- Flowing afterglow study of the gas phase nucleophilic reactions of some formyl, acetyl and cyclic esters
-
A variety of nucleophiles have been investigated for their reactions with formyl and acetyl esters in the gas phase in our flowing afterglow. The reactions that are permitted in the gas phase are more varied than those seen in the condensed phase. The rates of reactions of methyl and ethyl esters as well as various lactones have been undertaken with various nucleophiles: H2N-, HO-, CH3O, NCCH2-, F-, CH3C(=O)CH2-, CH3S- and O2NCH2-. For example, the reaction rate of NCCH2- + HCO2CH2CH3 has been found to be (1.3 ± 0.2) x 10-10 cm3 molecule-1 s-1 and the only product is HC(O-)=CHCN which results from nucleophilic acyl substitution (BAC2) followed by a proton transfer within the ion-molecule complex. Other reaction mechanisms that have been observed include β-elimination (E2), bimolecular nucleophilic substitution at the alkyl group (BAL2), and the Riveros reaction (elimination of CO). A mechanism for the F- + HCO2CH3 reaction has been determined at the B3LYP/6-31 + G(d) level. Most notably, channels were determined computationally (6AL2 and Riveros), and these channels are also observed experimentally. Furthermore, the BAC2 pathway which proceeds via nucleophilic attack on the carbonyl group also leads to the Riveros products, F-(CH3OH) and CO.
- Frink, Brian T.,Hadad, Christopher M.
-
-
Read Online
- Nanoconfinement Engineering over Hollow Multi-Shell Structured Copper towards Efficient Electrocatalytical C?C coupling
-
Nanoconfinement provides a promising solution to promote electrocatalytic C?C coupling, by dramatically altering the diffusion kinetics to ensure a high local concentration of C1 intermediates for carbon dimerization. Herein, under the guidance of finite-element method simulations results, a series of Cu2O hollow multi-shell structures (HoMSs) with tunable shell numbers were synthesized via Ostwald ripening. When applied in CO2 electroreduction (CO2RR), the in situ formed Cu HoMSs showed a positive correlation between shell numbers and selectivity for C2+ products, reaching a maximum C2+ Faradaic efficiency of 77.0±0.3 % at a conversion rate of 513.7±0.7 mA cm?2 in a neutral electrolyte. Mechanistic studies clarified the confinement effect of HoMSs that superposition of Cu shells leads to a higher coverage of localized CO adsorbate inside the cavity for enhanced dimerization. This work provides valuable insights for the delicate design of efficient C?C coupling catalysts.
- Li, Jiawei,Liu, Chunxiao,Xia, Chuan,Xue, Weiqing,Zeng, Jie,Zhang, Menglu,Zheng, Tingting
-
supporting information
(2021/12/06)
-
- Symmetry-Broken Au–Cu Heterostructures and their Tandem Catalysis Process in Electrochemical CO2 Reduction
-
Symmetry-breaking synthesis of colloidal nanocrystals with desired structures and properties has aroused widespread interest in various fields, but the lack of robust synthetic protocols and the complex growth kinetics limit their practical applications. Herein, a general strategy is developed to synthesize the Au–Cu Janus nanocrystals (JNCs) through the site-selective growth of Cu nanodomains on Au nanocrystals, which is directed by the substantial lattice mismatch between them, with the assistance of judicious manipulation of the growth kinetics. This strategy can work on Au nanocrystals with different architectures for the achievement of diverse asymmetric Au–Cu hybrid nanostructures. Of particular note, the obtained Au nanobipyramids (Au NBPs)-based JNCs facilitate the conversion of CO2 to C2 hydrocarbon production during electrocatalysis, with the Faradaic efficiency and maximum partial current density being 4.1-fold and 6.4-fold higher than those of their monometallic Cu counterparts, respectively. The excellent electrocatalytic performances benefit from the special design of the Au–Cu Janus architectures and their tandem catalysis mechanism as well as the high-index facets on Au nanocrystals. This research provides a new approach to synthesize various hybrid Janus nanostructures, facilitating the study of structure-function relationship in the catalytic process and the rational design of efficient heterogeneous electrocatalysts.
- Jia, Henglei,Yang, Yuanyuan,Chow, Tsz Him,Zhang, Han,Liu, Xiyue,Wang, Jianfang,Zhang, Chun-yang
-
-
- Ru catalyzed hydrogenation of CO2 to formate under basic and acidic conditions
-
The hydrogenation of CO2 to MeOH is pertinent to advance future energy schemes. Towards this end, phosophine-ligated Ru catalysts have been shown to achieve this transformation under either acidic or basic conditions. In this manuscript, we screen catalytic conditions for a novel tris(phosphine) ligand with Ru to see if it can facilitate the conversion of CO2 to MeOH under both acidic and basic conditions. With both sets of conditions, we observe hydrogenation of CO2 to formate. This work shows that the same catalytic system can function under both reaction types but is limited to formate production.
- Cannon, Austin T.,Saouma, Caroline T.
-
-
- Selectivity Control of Cu Nanocrystals in a Gas-Fed Flow Cell through CO2Pulsed Electroreduction
-
In this study, we have taken advantage of a pulsed CO2 electroreduction reaction (CO2RR) approach to tune the product distribution at industrially relevant current densities in a gas-fed flow cell. We compared the CO2RR selectivity of Cu catalysts subjected to either potentiostatic conditions (fixed applied potential of -0.7 VRHE) or pulsed electrolysis conditions (1 s pulses at oxidative potentials ranging from Ean = 0.6 to 1.5 VRHE, followed by 1 s pulses at -0.7 VRHE) and identified the main parameters responsible for the enhanced product selectivity observed in the latter case. Herein, two distinct regimes were observed: (i) for Ean = 0.9 VRHE we obtained 10% enhanced C2 product selectivity (FEC2H4 = 43.6% and FEC2H5OH = 19.8%) in comparison to the potentiostatic CO2RR at -0.7 VRHE (FEC2H4 = 40.9% and FEC2H5OH = 11%), (ii) while for Ean = 1.2 VRHE, high CH4 selectivity (FECH4 = 48.3% vs 0.1% at constant -0.7 VRHE) was observed. Operando spectroscopy (XAS, SERS) and ex situ microscopy (SEM and TEM) measurements revealed that these differences in catalyst selectivity can be ascribed to structural modifications and local pH effects. The morphological reconstruction of the catalyst observed after pulsed electrolysis with Ean = 0.9 VRHE, including the presence of highly defective interfaces and grain boundaries, was found to play a key role in the enhancement of the C2 product formation. In turn, pulsed electrolysis with Ean = 1.2 VRHE caused the consumption of OH- species near the catalyst surface, leading to an OH-poor environment favorable for CH4 production.
- Jeon, Hyo Sang,Timoshenko, Janis,Rettenmaier, Clara,Herzog, Antonia,Yoon, Aram,Chee, See Wee,Oener, Sebastian,Hejral, Uta,Haase, Felix T.,Roldan Cuenya, Beatriz
-
supporting information
p. 7578 - 7587
(2021/05/26)
-
- Operando Investigation of Ag-Decorated Cu2O Nanocube Catalysts with Enhanced CO2 Electroreduction toward Liquid Products
-
Direct conversion of carbon dioxide into multicarbon liquid fuels by the CO2 electrochemical reduction reaction (CO2RR) can contribute to the decarbonization of the global economy. Here, well-defined Cu2O nanocubes (NCs, 35 nm) uniformly covered with Ag nanoparticles (5 nm) were synthesized. When compared to bare Cu2O NCs, the catalyst with 5 at % Ag on Cu2O NCs displayed a two-fold increase in the Faradaic efficiency for C2+ liquid products (30 % at ?1.0 VRHE), including ethanol, 1-propanol, and acetaldehyde, while formate and hydrogen were suppressed. Operando X-ray absorption spectroscopy revealed the partial reduction of Cu2O during CO2RR, accompanied by a reaction-driven redispersion of Ag on the CuOx NCs. Data from operando surface-enhanced Raman spectroscopy further uncovered significant variations in the CO binding to Cu, which were assigned to Ag?Cu sites formed during CO2RR that appear crucial for the C?C coupling and the enhanced yield of liquid products.
- Herzog, Antonia,Bergmann, Arno,Jeon, Hyo Sang,Timoshenko, Janis,Kühl, Stefanie,Rettenmaier, Clara,Lopez Luna, Mauricio,Haase, Felix T.,Roldan Cuenya, Beatriz
-
supporting information
p. 7426 - 7435
(2021/02/26)
-
- Hydrogen and chemicals from alcohols through electrochemical reforming by Pd-CeO2/C electrocatalyst
-
The development of low-cost and sustainable hydrogen production is of primary importance for a future transition to sustainable energy. In this work, the selective and simultaneous production of pure hydrogen and chemicals from renewable alcohols is achieved using an anion exchange membrane electrolysis cell (electrochemical reforming) employing a nanostructured Pd-CeO2/C anode. The catalyst exhibits high activity for alcohol electrooxidation (e.g. 474 mA cm?2 with EtOH at 60 °C) and the electrolysis cell produces high volumes of hydrogen (1.73 l min?1 m?2) at low electrical energy input (Ecost = 6 kWh kgH2?1 with formate as substrate). A complete analysis of the alcohol oxidation products from several alcohols (methanol, ethanol, 1,2-propandiol, ethylene glycol, glycerol and 1,4-butanediol) shows high selectivity in the formation of valuable chemicals such as acetate from ethanol (100%) and lactate from 1,2-propandiol (84%). Importantly for industrial application, in batch experiments the Pd-CeO2/C catalyst achieves conversion efficiencies above 80% for both formate and methanol, and 95% for ethanol.
- Bellini, Marco,Pagliaro, Maria V.,Marchionni, Andrea,Filippi, Jonathan,Miller, Hamish A.,Bevilacqua, Manuela,Lavacchi, Alessandro,Oberhauser, Werner,Mahmoudian, Jafar,Innocenti, Massimo,Fornasiero, Paolo,Vizza, Francesco
-
-
- Erratum: Thermodynamic Analysis of Metal-Ligand Cooperativity of PNP Ru Complexes: Implications for CO2Hydrogenation to Methanol and Catalyst Inhibition (J. Am. Chem. Soc. (2019) 141:36 (14317-14328) DOI: 10.1021/jacs.9b06760)
-
Equation 13 in the Supporting Information contained a sign error, resulting in the incorrect pKa values reported for (PNP)Ru-CO2and PNP. The pKa of (PNP)Ru-CO2should be 26.1 ± 0.4 (not 24.6 ± 0.4). The pKa of PNP should be 29.0 ± 0.4 (not 28.6 ± 0.4). The same incorrect pKa values are reported on page 14322, in the left column, last paragraph for PNP, and in the right column, first paragraph for (PNP)Ru-CO2), and on page 14323, in Table 2, as well as in the SI (Table S3 and Figure S12 caption). Also in the Supporting Information, Figures S15 and S17 have the wrong functions plotted. The slope of the correct function was used in extrapolating thermochemical parameters derived from Figure S17. The slope of Figure S15 was used to extrapolate thermochemical parameters, which resulted in our reporting incorrect values. The value of K8,Cl should be 0.004 ± 0.0016 (not 2.5 × 10-7). The value of K5,Cl should be 2.0(±0.8) × 10-31(not 1.3 × 10-34), and hence the corresponding pKa should be >29.7 ± 0.2 (not >33.9 ± 0.4). The value of K6,Clshould be 1.0(±0.6) × 10-7(not 6.3 × 10-12), and hence the corresponding ΔG6,Cl should be 9.5 ± 0.3 kcalmol-1(not 15.3 ± 0.5 kcalmol-1). A corrected Supporting Information file is provided that has revised versions of eq 13, Figure S12 caption, Figure S15, Figure S17, and Table S3. The corrected Table 2 is shown below. None of these errors impact the discussion and conclusions drawn. We regret these errors and apologize for any confusion that may have resulted.
- Ardon, Yotam,Geary, Jackson,Mathis, Cheryl L.,Philliber, Mallory A.,Reese, Maxwell S.,Saouma, Caroline T.,Vanderlinden, Ryan T.
-
supporting information
p. 11274 - 11274
(2021/08/03)
-
- Reconstructing two-dimensional defects in CuO nanowires for efficient CO2electroreduction to ethylene
-
Here we report that in situ reconstructed Cu two-dimensional (2D) defects in CuO nanowires during CO2RR lead to significantly enhanced activity and selectivity of C2H4 compared to the CuO nanoplatelets. Specifically, the CuO nanowires achieve high faradaic efficiency of 62% for C2H4 and a partial current density of 324 mA cm-2 yet at a low potential of -0.56 V versus a reversible hydrogen electrode. Structural evolution characterization and in situ Raman spectra reveal that the high yield of C2H4 on CuO nanowires is attributed to the in situ reduction of CuO to Cu followed by structural reconstruction to form 2D defects, e.g., stacking faults and twin boundaries, which improve the CO production rate and ?CO adsorption strength. This finding may provide a paradigm for the rational design of nanostructured catalysts for efficient CO2 electroreduction to C2H4.
- Li, Zhengyuan,Wang, Yan,Wu, Jingjie,Wu, Yucheng,Xia, Shuai,Zhang, Jianfang,Zhang, Tianyu
-
supporting information
p. 8276 - 8279
(2021/08/25)
-
- Investigating the Origin of Enhanced C2+Selectivity in Oxide-/Hydroxide-Derived Copper Electrodes during CO2Electroreduction
-
Oxide-/hydroxide-derived copper electrodes exhibit excellent selectivity toward C2+ products during the electrocatalytic CO2 reduction reaction (CO2RR). However, the origin of such enhanced selectivity remains controversial. Here, we prepared two Cu-based electrodes with mixed oxidation states, namely, HQ-Cu (containing Cu, Cu2O, CuO) and AN-Cu (containing Cu, Cu(OH)2). We extracted an ultrathin specimen from the electrodes using a focused ion beam to investigate the distribution and evolution of various Cu species by electron microscopy and electron energy loss spectroscopy. We found that at the steady stage of the CO2RR, the electrodes have all been reduced to Cu0, regardless of the initial states, suggesting that the high C2+ selectivities are not associated with specific oxidation states of Cu. We verified this conclusion by control experiments in which HQ-Cu and AN-Cu were pretreated to fully reduce oxides/hydroxides to Cu0, and the pretreated electrodes showed even higher C2+ selectivity compared with their unpretreated counterparts. We observed that the oxide/hydroxide crystals in HQ-Cu and AN-Cu were fragmented into nanosized irregular Cu grains under the applied negative potentials. Such a fragmentation process, which is the consequence of an oxidation-reduction cycle and does not occur in electropolished Cu, not only built an intricate network of grain boundaries but also exposed a variety of high-index facets. These two features greatly facilitated the C-C coupling, thus accounting for the enhanced C2+ selectivity. Our work demonstrates that the use of advanced characterization techniques enables investigating the structural and chemical states of electrodes in unprecedented detail to gain new insights into a widely studied system.
- Lei, Qiong,Zhu, Hui,Song, Kepeng,Wei, Nini,Liu, Lingmei,Zhang, Daliang,Yin, Jun,Dong, Xinglong,Yao, Kexin,Wang, Ning,Li, Xinghua,Davaasuren, Bambar,Wang, Jianjian,Han, Yu
-
p. 4213 - 4222
(2020/03/04)
-
- A bioinspired molybdenum-copper molecular catalyst for CO2electroreduction
-
Non-noble metal molecular catalysts mediating the electrocatalytic reduction of carbon dioxide are still scarce. This work reports the electrochemical reduction of CO2to formate catalyzed by the bimetallic complex [(bdt)MoVI(O)S2CuICN]2?(bdt = benzenedithiolate), a mimic of the active site of the Mo-Cu carbon monoxide dehydrogenase enzyme (CODH2). Infrared spectroelectrochemical (IR-SEC) studies coupled with density functional theory (DFT) computations revealed that the complex is only a pre-catalyst, the active catalyst being generated upon reduction in the presence of CO2. We found that the two-electron reduction of [(bdt)MoVI(O)S2CuICN]2?triggers the transfer of the oxo moiety to CO2forming CO32?and the complex [(bdt)MoIVS2CuICN]2?and that a further one-electron reduction is needed to generate the active catalyst. Its protonation yields a reactive MoVH hydride intermediate which reacts with CO2to produce formate. These findings are particularly relevant to the design of catalysts from metal oxo precursors.
- Dey, Subal,Fontecave, Marc,Mouchfiq, Ahmed,Mougel, Victor,Todorova, Tanya K.
-
p. 5503 - 5510
(2020/06/10)
-
- Reduction of carbon dioxide at a plasmonically active copper-silver cathode
-
Electrochemically deposited copper nanostructures were coated with silver to create a plasmonically active cathode for carbon dioxide (CO2) reduction. Illumination with 365 nm light, close to the peak plasmon resonance of silver, selectively enhanced 5 of the 14 typically observed copper CO2 reduction products while simultaneously suppressing hydrogen evolution. At low overpotentials, carbon monoxide was promoted in the light and at high overpotentials ethylene, methane, formate, and allyl alcohol were enhanced upon illumination; generally C1 products and C2/C3 products containing a double carbon bond were selectively promoted under illumination. Temperature-dependent product analysis in the dark showed that local heating is not the cause of these selectivity changes. While the exact plasmonic mechanism is still unknown, these results demonstrate the potential for enhancing CO2 reduction selectivity at copper electrodes using plasmonics.
- Corson, Elizabeth R.,Subramani, Ananya,Cooper, Jason K.,Kostecki, Robert,Urban, Jeffrey J.,McCloskey, Bryan D.
-
supporting information
p. 9970 - 9973
(2020/09/23)
-
- One pot solvent assisted syntheses of Ag3SbS3nanocrystals and exploring their phase dependent electrochemical behavior toward oxygen reduction reaction and visible light induced methanol oxidation reaction
-
A huge variety of silver based ternary sulfide semiconductors (SCs) have been considered for the sustainable advancement of renewable energy sources. Herein, we have synthesized two important classes of newly emerging semiconductor nanocrystals (NCs) Ag3SbS3 (SAS), i.e. hexagonal and monoclinic by simply tuning the solvent polarity, of which the second one has been synthesized in a phase pure NC for the first time by the thermal decomposition of silver and antimony based dithiocarbamate (~N-CS2-M) complexes. Interestingly, these two systems exhibit two different semiconducting (SC) properties and band gaps; hexagonal SAS has a p type (Eg ~ 1.65 eV) whereas monoclinic SAS has an n type (Eg ~ 2.1 eV) character. For the first time ever we have designed a reducing working electrode (i.e. cathode) by modifying the rotating disc electrode (RDE) with hexagonal SAS that exhibits excellent electrochemical oxygen reduction reaction (ORR) activity (Eonset = 1.09 V vs. RHE and average number of electron transfer: 3.89) comparable to that of the highly expensive Pt/C (Eonset = 0.88 V vs. RHE and average number of electron transfer: 3.92). Density functional theory (DFT) investigation confirms the corroborations of experimental data with theoretical implications. In addition, the electrode fabricated from monoclinic SAS acts as an efficient photoanode which exhibits higher photoelectrochemical (PEC) methanol oxidation reaction (MOR) activity under illumination in alkaline medium compared to that of standard TiO2 grown on an indium tin oxide (ITO) coated glass slide. On illumination, the relative photocurrent density at the onset potential has been obtained to be 845 which is a very significant experimental output with respect to any other TiO2 or Pt?TiO2 based photocatalysts for this application. The physicochemical stability and reusability of both materials were supported by 50 hours of extended electrochemical chronoamperometric measurements and powder XRD and the TEM analyses after electrocatalysis. This study explores a possible pathway for designing simple and less expensive but catalytically efficient silver based ternary sulfide NC systems for developing an SC material to reduce the energy crisis in the near future.
- Adhikary, Bibhutosh,Bhadu, Gopala Ram,Ghorui, Uday Kumar,Mondal, Papri,Satra, Jit
-
supporting information
p. 9464 - 9479
(2020/09/09)
-
- Metal-ligand bond strength determines the fate of organic ligands on the catalyst surface during the electrochemical CO2reduction reaction
-
Colloidally synthesised nanocrystals (NCs) are increasingly utilised as catalysts to drive both thermal and electrocatalytic reactions. Their well-defined size and shape, controlled by organic ligands, are ideal to identify the parameters relevant to the activity, selectivity and stability in catalysis. However, the impact of the native surface ligands during catalysis still remains poorly understood, as does their fate. CuNCs are among the state-of-the-art catalysts for the electrochemical CO2 reduction reaction (CO2RR). In this work, we study CuNCs that are capped by different organic ligands to investigate their impact on the catalytic properties. We show that the latter desorb from the surface at a cathodic potential that depends on their binding strength with the metal surface, rather than their own electroreduction potentials. By monitoring the evolving surface chemistry in situ, we find that weakly bound ligands desorb very rapidly while strongly bound ligands impact the catalytic performance. This work provides a criterion to select labile ligands versus ligands that will persist on the surface, thus offering opportunity for interface design. This journal is
- Buonsanti, Raffaella,Iyengar, Pranit,Loiudice, Anna,Mensi, Mounir,Pankhurst, James R.
-
p. 9296 - 9302
(2020/09/17)
-
- Electroreduction of CO2to Formate on a Copper-Based Electrocatalyst at High Pressures with High Energy Conversion Efficiency
-
Electrocatalytic CO2 reduction (CO2RR) to valuable fuels is a promising approach to mitigate energy and environmental problems, but controlling the reaction pathways and products remains challenging. Here a novel Cu2O nanoparticle film was synthesized by square-wave (SW) electrochemical redox cycling of high-purity Cu foils. The cathode afforded up to 98percent Faradaic efficiency for electroreduction of CO2 to nearly pure formate under ≥45 atm CO2 in bicarbonate catholytes. When this cathode was paired with a newly developed NiFe hydroxide carbonate anode in KOH/borate anolyte, the resulting two-electrode high-pressure electrolysis cell achieved high energy conversion efficiencies of up to 55.8percent stably for long-term formate production. While the high-pressure conditions drastically increased the solubility of CO2 to enhance CO2 reduction and suppress hydrogen evolution, the (111)-oriented Cu2O film was found to be important to afford nearly 100percent CO2 reduction to formate. The results have implications for CO2 reduction to a single liquid product with high energy conversion efficiency.
- Chiang, Ching-Yu,Dai, Hongjie,Guo, Jinyu,Hung, Wei-Hsuan,Ku, Ching-Shun,Kuang, Yun,Li, Aowen,Li, Jiachen,Meng, Yongtao,Sun, Xiaoming,Tian, Xin,Xu, Mingquan,Zhang, Xiao,Zhou, Wu,Zhu, Guanzhou
-
supporting information
p. 7276 - 7282
(2020/08/06)
-
- Reactivity of borohydride incorporated in coordination polymers toward carbon dioxide
-
Borohydride (BH4-)-containing coordination polymers converted CO2into HCO2-or [BH3(OCHO)]-, whose reaction routes were affected by the electronegativity of metal ions and the coo
- Kadota, Kentaro,Sivaniah, Easan,Horike, Satoshi
-
p. 5111 - 5114
(2020/05/26)
-
- PHOTO-REDOX TITANIUM CONTAINING ORGANIC FRAMEWORKS AND METHODS OF MAKING AND USE THEREOF
-
Disclosed herein are metal-organic frameworks and methods of making and use thereof.
- -
-
Paragraph 0165; 0172-0173
(2020/07/07)
-
- Highly selective and durable photochemical co2 reduction by molecular mn(i) catalyst fixed on a particular dye-sensitized TiO2 Platform
-
A Mn(I)-based hybrid system (OrgD-|TiO2|-MnP) for photocatalytic CO2 reduction is designed to be a coassembly of Mn(4,4′-Y2-bpy)(CO)3Br (MnP; Y = CH2PO(OH)2) and (E)-3-[5-(4-(diphenylamino)phenyl)-2,2′-bithiophen-2′-yl]-2-cyanoacrylic acid (OrgD) on TiO2 semiconductor particles. The OrgD-|TiO2|-MnP hybrid reveals persistent photocatalytic behavior, giving high turnover numbers and good product selectivity (HCOO- versus CO). As a typical run, visible-light irradiation of the hybrid catalyst in the presence of 0.1 M electron donor (ED) and 0.001 M LiClO4 persistently produced HCOO- with a >99% selectivity accompanied by a trace amount of CO; the turnover number (TONformate) reached ?250 after 23 h of irradiation. The product selectivity (HCOO-/CO) was found to be controlled by changing the loading amount of MnP on the TiO2 surface. In situ FTIR analysis of the hybrid during photocatalysis revealed that, at low Mn concentration, the Mn-H monomeric mechanism associated with HCOO- formation is dominant, whereas at high Mn concentration, CO is formed via a Mn-Mn dimer mechanism.
- Woo, Sung-Jun,Choi, Sunghan,Kim, So-Yoen,Kim, Pil Soo,Jo, Ju Hyoung,Kim, Chul Hoon,Son, Ho-Jin,Pac, Chyongjin,Kang, Sang Ook
-
p. 2580 - 2593
(2019/03/08)
-
- Characterizing Cation Chemistry for Anion Exchange Membranes - A Product Study of Benzylimidazolium Salt Decompositions in the Base
-
Imidazolium functionality has played a prominent role in research on anion exchange membranes for use in alkaline electrochemical devices. Base stability and degradation of these materials has been much studied, but in many instances, product pathways have not been thoroughly delineated. We report an NMR study of base-induced decomposition products from three benzylimidazolium salts bearing varying extents of methyl substitution on the imidazolium ring. The major products are consistent with a hydrolytic ring fragmentation pathway as the principal mode of decomposition. We observe several new products not previously reported in the literature on imidazolium salt degradation, including benzilic acid rearrangement products formally derived from intermediate 1,2-dicarbonyl compounds or their equivalents. However, the overall reactions are complex, the yields of observed products do not account for all consumed starting materials, and mechanistic ambiguities remain.
- Pellerite, Mark J.,Kaplun, Marina M.,Webb, Robert J.
-
p. 15486 - 15497
(2019/11/19)
-
- Direct Synthesis of Methyl Formate from CO2 With Phosphine-Based Polymer-Bound Ru Catalysts
-
Methyl formate was produced in one pot through the hydrogenation of CO2 to formic acid/formate followed by an esterification step. The route offers the possibility to integrate renewable energy into the fossil-based chemical value chain. In this work, a phosphine-polymer-anchored Ru complex was shown to be an efficient solid catalyst for the direct hydrogenation of CO2 to methyl formate. The 1,2-bis(diphenylphosphino)ethane-like polymer presented the highest activity with a turnover number (TON) of up to 3401 at 160 °C. The reaction parameters were systemically investigated to optimize the reaction towards the formation of methyl formate. This catalyst could be reused seven times without a significant decrease in activity. Evolution of the catalytic Ru center during the reaction was revealed, and a possible reaction mechanism was proposed.
- Sun, Ruiyan,Kann, Anna,Hartmann, Heinrich,Besmehn, Astrid,Hausoul, Peter J. C.,Palkovits, Regina
-
p. 3278 - 3285
(2019/06/13)
-
- On the Oxidation State of Cu2O upon Electrochemical CO2 Reduction: An XPS Study
-
The encouraging selectivity of copper oxides for the electroreduction of CO2 into ethylene and alcohols has led to a vivid debate on the possible relation between their operando (sub-)surface oxidation state (i. e. fully reduced or partially oxidized) and this distinct reactivity. The high roughness of the Cu oxides used in previous studies on this matter adds complexity to this controversy and motivated us to prepare quasi-planar Cu2O thin films that displayed a CO2 reduction selectivity similar to that of oxide-derived copper catalysts reported in previous studies. Most importantly, when the post-mortem thin films were transferred for characterization in an air-free environment, X-ray photoelectron spectroscopy measurements confirmed their complete reduction in the course of the CO2 reduction reaction. Thus, our results indicate that the selectivity of the Cu oxides featured in previous studies stems from their enhanced roughness, highlighting the importance of controlled sample transfer upon post-mortem characterization with ex situ techniques.
- Permyakova, Anastasia A.,Herranz, Juan,El Kazzi, Mario,Diercks, Justus S.,Povia, Mauro,Mangani, Léa Rose,Horisberger, Michael,P?tru, Alexandra,Schmidt, Thomas J.
-
p. 3120 - 3127
(2019/08/07)
-
- Room temperature, near-quantitative conversion of glucose into formic acid
-
Herein, a facile and efficient method was developed to selectively transform glucose into formic acid at room temperature. After parameter optimization, formic acid was obtained in an unprecedented 91.3% yield with a reaction time of 8 h in lithium hydroxide aqueous solution with hydrogen peroxide as the oxidant. The synergistic effects of the base and the oxidant promoted the glucose conversion at room temperature and enhanced the selectivity towards FA. Besides, the employed mild conditions have suppressed FA decomposition that often occurred under harsh conditions, which further improved the FA selectivity. A series of model compound tests were conducted to probe the possible intermediates based on which a plausible reaction pathway was proposed. In addition, the process is applicable to various carbohydrates such as cellobiose, starch, xylan, etc. This work opens up a simple, mild but effective method to produce FA from renewable biomass resources, which would remarkably alleviate the energy consumption, capital costs, handling risks, etc.
- Wang, Can,Chen, Xi,Qi, Man,Wu, Jianeng,G?zaydin, G?kalp,Yan, Ning,Zhong, Heng,Jin, Fangming
-
p. 6089 - 6096
(2019/11/20)
-
- Bipyridine-Assisted Assembly of Au Nanoparticles on Cu Nanowires To Enhance the Electrochemical Reduction of CO2
-
We report a new strategy to prepare a composite catalyst for highly efficient electrochemical CO2 reduction reaction (CO2RR). The composite catalyst is made by anchoring Au nanoparticles on Cu nanowires via 4,4′-bipyridine (bipy). The Au-bipy-Cu composite catalyzes the CO2RR in 0.1 m KHCO3 with a total Faradaic efficiency (FE) reaching 90.6 % at ?0.9 V to provide C-products, among which CH3CHO (25 % FE) dominates the liquid product (HCOO?, CH3CHO, and CH3COO?) distribution (75 %). The enhanced CO2RR catalysis demonstrated by Au-bipy-Cu originates from its synergistic Au (CO2 to CO) and Cu (CO to C-products) catalysis which is further promoted by bipy. The Au-bipy-Cu composite represents a new catalyst system for effective CO2RR conversion to C-products.
- Fu, Jiaju,Zhu, Wenlei,Chen, Ying,Yin, Zhouyang,Li, Yuyang,Liu, Juan,Zhang, Hongyi,Zhu, Jun-Jie,Sun, Shouheng
-
supporting information
p. 14100 - 14103
(2019/09/03)
-
- Thermodynamic Analysis of Metal-Ligand Cooperativity of PNP Ru Complexes: Implications for CO2 Hydrogenation to Methanol and Catalyst Inhibition
-
The hydrogenation of CO2 in the presence of amines to formate, formamides, and methanol (MeOH) is a promising approach to streamlining carbon capture and recycling. To achieve this, understanding how catalyst design impacts selectivity and performance is critical. Herein we describe a thorough thermochemical analysis of the (de)hydrogenation catalyst, (PNP)Ru-Cl (PNP = 2,6-bis(di-tert-butylphosphinomethyl)pyridine; Ru = Ru(CO)(H)) and correlate our findings to catalyst performance. Although this catalyst is known to hydrogenate CO2 to formate with a mild base, we show that MeOH is produced when using a strong base. Consistent with pKa measurements, the requirement for a strong base suggests that the deprotonation of a six-coordinate Ru species is integral to the catalytic cycle that produces MeOH. Our studies also indicate that the concentration of MeOH produced is independent of catalyst concentration, consistent with a deactivation pathway that is dependent on methanol concentration, not equivalency. Our temperature-dependent equilibrium studies of the dearomatized congener, (*PNP)Ru, with various H-X species (to give (PNP)Ru-X; X = H, OH, OMe, OCHO, OC(O)NMe2) reveal that formic acid equilibrium is approximately temperature-independent; relative to H2, it is more favored at elevated temperatures. We also measure the hydricity of (PNP)Ru-H in THF and show how subsequent coordination of the substrate can impact the apparent hydricity. The implications of this work are broadly applicable to hydrogenation and dehydrogenation catalysis and, in particular, to those that can undergo metal-ligand cooperativity (MLC) at the catalyst. These results serve to benchmark future studies by allowing comparisons to be made among catalysts and will positively impact rational catalyst design.
- Mathis, Cheryl L.,Geary, Jackson,Ardon, Yotam,Reese, Maxwell S.,Philliber, Mallory A.,Vanderlinden, Ryan T.,Saouma, Caroline T.
-
supporting information
p. 14317 - 14328
(2019/10/11)
-
- Electrocatalytic Reduction of CO2 to Methanol by Iron Tetradentate Phosphine Complex Through Amidation Strategy
-
The iron complex of tetradentate tris[2-(diphenylphosphino) ethyl]phosphine (PP3), [Fe(PP3)(MeCN)2](BF4)2, was able to electrocatalytically reduce CO2 to formate with a Faradaic efficiency (FE) of approximately 97.3 % in acetonitrile. Upon addition of diethylamine as a cocatalyst, electrocatalytic reduction to methanol was achieved with an FE of 68.5 %, and other products were formamide and formate. A mechanistic study suggested that the [FeH(PP3)](BF4) hydride complex was the active species in the electrocatalysis. Added amine as cocatalyst could react with CO2 to form carbamate, which could then be reduced to formamide and further to methanol. By contrast, free CO2 could only be reduced to formate as the end-product.
- Bi, Jiaojiao,Hou, Pengfei,Liu, Fang-Wei,Kang, Peng
-
p. 2195 - 2201
(2019/05/15)
-
- CO2 and CO/H2 Conversion to Methoxide by a Uranium(IV) Hydride
-
Here we show that a scaffold combining siloxide ligands and a bridging oxide allows the synthesis and characterization of the stable dinuclear uranium(IV) hydride complex [K2{[U(OSi(OtBu)3)3]2(μ-O)(μ-H)2}], 2, which displays high reductive reactivity. The dinuclear bis-hydride 2 effects the reductive coupling of acetonitrile by hydride transfer to yield [K2{[U(OSi(OtBu)3)3]2(μ-O)(μ-κ2-NC(CH3)NCH2CH3)}], 3. Under ambient conditions, the reaction of 2 with CO affords the oxomethylene2- reduction product [K2{[U(OSi(OtBu)3)3]2(μ-CH2O)(μ-O)}], 4, that can further add H2 to afford the methoxide hydride complex [K2{[U(OSi(OtBu)3)3]2(μ-OCH3)(μ-O)(μ-H)}], 5, from which methanol is released in water. Complex 2 also effects the direct reduction of CO2 to the methoxide complex 5, which is unprecedented in f element chemistry. From the reaction of 2 with excess CO2, crystals of the bis-formate carbonate complex [K2{[U(OSi(OtBu)3)3]2(μ-CO3)(μ-HCOO)2}], 6, could also be isolated. All the reaction products were characterized by X-ray crystallography and NMR spectroscopy.
- Falcone, Marta,Scopelliti, Rosario,Mazzanti, Marinella
-
p. 9570 - 9577
(2019/05/17)
-
- Structural Sensitivities in Bimetallic Catalysts for Electrochemical CO2 Reduction Revealed by Ag-Cu Nanodimers
-
Understanding the structural and compositional sensitivities of the electrochemical CO2 reduction reaction (CO2RR) is fundamentally important for developing highly efficient and selective electrocatalysts. Here, we use Ag/Cu nanocrystals to uncover the key role played by the Ag/Cu interface in promoting CO2RR. Nanodimers including the two constituent metals as segregated domains sharing a tunable interface are obtained by developing a seeded growth synthesis, wherein preformed Ag nanoparticles are used as nucleation seeds for the Cu domain. We find that the type of metal precursor and the strength of the reducing agent play a key role in achieving the desired chemical and structural control. We show that tandem catalysis and electronic effects, both enabled by the addition of Ag to Cu in the form of segregated nanodomain within the same catalyst, synergistically account for an enhancement in the Faradaic efficiency for C2H4 by 3.4-fold and in the partial current density for CO2 reduction by 2-fold compared with the pure Cu counterpart. The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for electrochemical CO2 reduction.
- Huang, Jianfeng,Mensi, Mounir,Oveisi, Emad,Mantella, Valeria,Buonsanti, Raffaella
-
supporting information
p. 2490 - 2499
(2019/03/04)
-
- Atomic Layer Deposition of ZnO on CuO Enables Selective and Efficient Electroreduction of Carbon Dioxide to Liquid Fuels
-
Electrochemical reduction of carbon dioxide, if powered by renewable electricity, could serve as a sustainable technology for carbon recycling and energy storage. Among all the products, ethanol is an attractive liquid fuel. However, the maximum faradaic efficiency of ethanol is only ≈10 % on polycrystalline Cu. Here, CuZn bimetallic catalysts were synthesized by in situ electrochemical reduction of ZnO-shell/CuO-core bi-metal-oxide. Dynamic evolution of catalyst was revealed by STEM-EDS mapping, showing the migration of Zn atom and blending between Cu and Zn. CuZn bimetallic catalysts showed preference towards ethanol formation, with the ratio of ethanol/ethylene increasing over five times regardless of applied potential. We achieved 41 % faradaic efficiency for C2+ liquids with this catalyst. Transitioning from H-cell to an electrochemical flow cell, we achieved 48.6 % faradaic efficiency and ?97 mA cm?2 partial current density for C2+ liquids at only ?0.68 V versus reversible hydrogen electrode in 1 m KOH. Operando Raman spectroscopy showed that CO binding on Cu sites was modified by Zn. Free CO and adsorbed *CH3 are believed to combine and form *COCH3 intermediate, which is exclusively reduced to ethanol.
- Ren, Dan,Gao, Jing,Pan, Linfeng,Wang, Zaiwei,Luo, Jingshan,Zakeeruddin, Shaik M.,Hagfeldt, Anders,Gr?tzel, Michael
-
supporting information
p. 15036 - 15040
(2019/09/13)
-
- 2D Metal Oxyhalide-Derived Catalysts for Efficient CO2 Electroreduction
-
Electrochemical reduction of CO2 is a compelling route to store renewable electricity in the form of carbon-based fuels. Efficient electrochemical reduction of CO2 requires catalysts that combine high activity, high selectivity, and low overpotential. Extensive surface reconstruction of metal catalysts under high productivity operating conditions (high current densities, reducing potentials, and variable pH) renders the realization of tailored catalysts that maximize the exposure of the most favorable facets, the number of active sites, and the oxidation state all the more challenging. Earth-abundant transition metals such as tin, bismuth, and lead have been proven stable and product-specific, but exhibit limited partial current densities. Here, a strategy that employs bismuth oxyhalides as a template from which 2D bismuth-based catalysts are derived is reported. The BiOBr-templated catalyst exhibits a preferential exposure of highly active Bi (110) facets. Thereby, the CO2 reduction reaction selectivity is increased to over 90% Faradaic efficiency and simultaneously stable current densities of up to 200 mA cm?2 are achieved—more than a twofold increase in the production of the energy-storage liquid formic acid compared to previous best Bi catalysts.
- García de Arquer, F. Pelayo,Bushuyev, Oleksandr S.,De Luna, Phil,Dinh, Cao-Thang,Seifitokaldani, Ali,Saidaminov, Makhsud I.,Tan, Chih-Shan,Quan, Li Na,Proppe, Andrew,Kibria, Md. Golam,Kelley, Shana O.,Sinton, David,Sargent, Edward H.
-
-
- A Highly Porous Copper Electrocatalyst for Carbon Dioxide Reduction
-
Electrochemical reduction of carbon dioxide (CO2) is an appealing approach toward tackling climate change associated with atmospheric CO2 emissions. This approach uses CO2 as the carbon feedstock to produce value-added chemicals, resulting in a carbon-neutral (or even carbon-negative) process for chemical production. Many efforts have been devoted to the development of CO2 electrolysis devices that can be operated at industrially relevant rates; however, limited progress has been made, especially for valuable C2+ products. Herein, a nanoporous copper CO2 reduction catalyst is synthesized and integrated into a microfluidic CO2 flow cell electrolyzer. The CO2 electrolyzer exhibits a current density of 653 mA cm?2 with a C2+ product selectivity of ≈62% at an applied potential of ?0.67 V (vs reversible hydrogen electrode). The highly porous electrode structure facilitates rapid gas transport across the electrode–electrolyte interface at high current densities. Further investigations on electrolyte effects reveal that the surface pH value is substantially different from the pH of bulk electrolyte, especially for nonbuffering near-neutral electrolytes when operating at high currents.
- Lv, Jing-Jing,Jouny, Matthew,Luc, Wesley,Zhu, Wenlei,Zhu, Jun-Jie,Jiao, Feng
-
-
- Integrative CO2 Capture and hydrogenation to methanol with reusable catalyst and amine: Toward a carbon neutral methanol economy
-
Herein we report an efficient and recyclable system for tandem CO2 capture and hydrogenation to methanol. After capture in an aqueous amine solution, CO2 is hydrogenated in high yield to CH3OH (>90%) in a biphasic 2-MTHF/water system, which also allows for easy separation and recycling of the amine and catalyst for multiple reaction cycles. Between cycles, the produced methanol can be conveniently removed in vacuo. Employing this strategy, catalyst Ru-MACHO-BH and polyamine PEHA were recycled three times with 87% of the methanol producibility of the first cycle retained, along with 95% of catalyst activity after four cycles. CO2 from dilute sources such as air can also be converted to CH3OH using this route. We postulate that the CO2 capture and hydrogenation to methanol system presented here could be an important step toward the implementation of the carbon neutral methanol economy concept.
- Kar, Sayan,Sen, Raktim,Goeppert, Alain,Prakash, G.K. Surya
-
supporting information
p. 1580 - 1583
(2018/02/17)
-
- CO2 Reduction Promoted by Imidazole Supported on a Phosphonium-Type Ionic-Liquid-Modified Au Electrode at a Low Overpotential
-
The catalytic conversion of CO2 to useful compounds is of great importance from the viewpoint of global warming and development of alternatives to fossil fuels. Electrochemical reduction of CO2 using aromatic N-heterocylic molecules is a promising research area. We describe a high performance electrochemical system for reducing CO2 to formate, methanol, and CO using imidazole incorporated into a phosphonium-type ionic liquid-modified Au electrode, imidazole@IL/Au, at a low onset-potential of -0.32 V versus Ag/AgCl. This represents a significant improvement relative to the onset-potential obtained using a conventional Au electrode (-0.56 V). In the reduction carried out at -0.4 V, formate is mainly generated and methanol and CO are also generated with high efficiency at -0.6 ~ -0.8 V. The generation of methanol is confirmed by experiments using 13CO2 to generate 13CH3OH. To understand the reaction behavior of CO2 reduction, we characterized the reactions by conducting potential- and time-dependent in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (SEIRAS) measurements in D2O. During electrochemical CO2 reduction at -0.8 V, the C-O stretching band for CDOD (or COD) increases and the C=O stretching band for COOD increases at -0.4 V. These findings indicate that CO2 reduction intermediates, CDOD (or COD) and COOD, are formed, depending on the reduction potential, to convert CO2 to methanol and formate, respectively.
- Iijima, Go,Kitagawa, Tatsuya,Katayama, Akira,Inomata, Tomohiko,Yamaguchi, Hitoshi,Suzuki, Kazunori,Hirata, Kazuki,Hijikata, Yoshimasa,Ito, Miho,Masuda, Hideki
-
p. 1990 - 2000
(2018/03/09)
-
- Electrochemical Reduction of Carbon Dioxide to Methanol on Hierarchical Pd/SnO2 Nanosheets with Abundant Pd–O–Sn Interfaces
-
Electrochemical conversion of CO2 into fuels using electricity generated from renewable sources helps to create an artificial carbon cycle. However, the low efficiency and poor stability hinder the practical use of most conventional electrocatalysts. In this work, a 2D hierarchical Pd/SnO2 structure, ultrathin Pd nanosheets partially capped by SnO2 nanoparticles, is designed to enable multi-electron transfer for selective electroreduction of CO2 into CH3OH. Such a structure design not only enhances the adsorption of CO2 on SnO2, but also weakens the binding strength of CO on Pd due to the as-built Pd–O–Sn interfaces, which is demonstrated to be critical to improve the electrocatalytic selectivity and stability of Pd catalysts. This work provides a new strategy to improve electrochemical performance of metal-based catalysts by creating metal oxide interfaces for selective electroreduction of CO2.
- Zhang, Wuyong,Qin, Qing,Dai, Lei,Qin, Ruixuan,Zhao, Xiaojing,Chen, Xumao,Ou, Daohui,Chen, Jie,Chuong, Tracy T,Wu, Binghui,Zheng, Nanfeng
-
supporting information
p. 9475 - 9479
(2018/07/29)
-
- Sharp Cu@Sn nanocones on Cu foam for highly selective and efficient electrochemical reduction of CO2 to formate
-
Electrochemical reduction of aqueous CO2 into formate is subject to poor selectivity and low current density with conventional Sn-based catalysts owing to the inert nature of CO2 molecules and the low number of active sites. Recently, it has been demonstrated that alkali metal cations could greatly enhance selectivity for CO2 reduction by stabilizing the key intermediates, which leads to an effective solution to this problem by concentrating local metal cations through tailoring the catalyst structure. Herein, we synthesized spiky Cu@Sn nanocones over a macroporous Cu foam, which has a curvature radius of 10 nm, via facile electrochemical coating of a thin layer of Sn over the Cu nanoconic surface. A faradaic efficiency of 90.4% toward formate production was achieved, with a current density of 57.7 mA cm-2 at -1.1 V vs. a reversible hydrogen electrode, which far exceeds results achieved to date with state-of-the-art Sn catalysts. The performance should be attributed to the combined effects of a sharp conical feature that facilitates the enrichment of surface-adsorbed metal cations and the promotion of the mass transfer and active sites growth favored by the three-dimensional porous network.
- Chen, Chengzhen,Pang, Yuanjie,Zhang, Fanghua,Zhong, Juhua,Zhang, Bo,Cheng, Zhenmin
-
p. 19621 - 19630
(2018/10/24)
-
- Insights into Cell-Free Conversion of CO2 to Chemicals by a Multienzyme Cascade Reaction
-
Multienzymatic cascade reactions have garnered the attention of many researchers as an approach for converting CO2 into methanol. The cascade reaction used in this study includes the following enzymes: a formate dehydrogenase (ClFDH), a formaldehyde dehydrogenase (BmFaldDH), and an alcohol dehydrogenase (YADH) from Clostridium ljungdahlii, Burkholderia multivorans, and Saccharomyces cerevisiae, respectively. Because this cascade reaction requires NADH as a cofactor, phosphite dehydrogenase (PTDH) was employed to regenerate the cofactor. The multienzymatic cascade reaction, along with PTDH, yielded 3.28 mM methanol. The key to the success of this cascade reaction was a novel formaldehyde dehydrogenase, BmFaldDH, the enzyme catalyzing the reduction of formate to formaldehyde. The methanol yield was further improved by incorporation of 1-ethyl-3-methylimidazolium acetate (EMIM-Ac), resulting in 7.86 mM of methanol. A 500-fold increase in total turnover number was observed for the ClFDH-BmFaldDH-YADH cascade system compared to the Candida boidinii FDH-Pseudomonas putida FaldDH-YADH system. We provided detailed insights into the enzymatic reduction of CO2 by determining the thermodynamic parameters (Kd and ΔG) using isothermal titration calorimetry. Furthermore, we demonstrated a novel time-dependent formaldehyde production from CO2. Our results will aid in the understanding and development of a robust multienzyme catalyzed cascade reaction for the reduction of CO2 to value-added chemicals.
- Singh, Raushan Kumar,Singh, Ranjitha,Sivakumar, Dakshinamurthy,Kondaveeti, Sanath,Kim, Taedoo,Li, Jinglin,Sung, Bong Hyun,Cho, Byung-Kwan,Kim, Dong Rip,Kim, Sun Chang,Kalia, Vipin C.,Zhang, Yi-Heng P. Job,Zhao, Huimin,Kang, Yun Chan,Lee, Jung-Kul
-
p. 11085 - 11093
(2019/01/03)
-
- Metal-Organic Frameworks Mediate Cu Coordination for Selective CO2 Electroreduction
-
The electrochemical carbon dioxide reduction reaction (CO2RR) produces diverse chemical species. Cu clusters with a judiciously controlled surface coordination number (CN) provide active sites that simultaneously optimize selectivity, activity, and efficiency for CO2RR. Here we report a strategy involving metal-organic framework (MOF)-regulated Cu cluster formation that shifts CO2 electroreduction toward multiple-carbon product generation. Specifically, we promoted undercoordinated sites during the formation of Cu clusters by controlling the structure of the Cu dimer, the precursor for Cu clusters. We distorted the symmetric paddle-wheel Cu dimer secondary building block of HKUST-1 to an asymmetric motif by separating adjacent benzene tricarboxylate moieties using thermal treatment. By varying materials processing conditions, we modulated the asymmetric local atomic structure, oxidation state and bonding strain of Cu dimers. Using electron paramagnetic resonance (EPR) and in situ X-ray absorption spectroscopy (XAS) experiments, we observed the formation of Cu clusters with low CN from distorted Cu dimers in HKUST-1 during CO2 electroreduction. These exhibited 45% C2H4 faradaic efficiency (FE), a record for MOF-derived Cu cluster catalysts. A structure-activity relationship was established wherein the tuning of the Cu-Cu CN in Cu clusters determines the CO2RR selectivity.
- Nam, Dae-Hyun,Bushuyev, Oleksandr S.,Li, Jun,De Luna, Phil,Seifitokaldani, Ali,Dinh, Cao-Thang,García De Arquer, F. Pelayo,Wang, Yuhang,Liang, Zhiqin,Proppe, Andrew H.,Tan, Chih Shan,Todorovi?, Petar,Shekhah, Osama,Gabardo, Christine M.,Jo, Jea Woong,Choi, Jongmin,Choi, Min-Jae,Baek, Se-Woong,Kim, Junghwan,Sinton, David,Kelley, Shana O.,Eddaoudi, Mohamed,Sargent, Edward H.
-
p. 11378 - 11386
(2018/09/06)
-
- Coupling glucose dehydrogenation with co2 hydrogenation by hydrogen transfer in aqueous media at room temperature
-
Conversion of CO2 into value-added chemicals and fuels provides a direct solution to reduce excessive CO2 in the atmosphere. Herein, a novel catalytic reaction system is presented by coupling the dehydrogenation of glucose with the hydrogenation of a CO2-derived salt, ammonium carbonate, in an ethanol–water mixture. For the first time, the hydrogenation of CO2 to formate by glucose has been achieved under ambient conditions. Under the optimal reaction conditions, the highest yield of formate reached approximately 46 %. We find that the apparent pH value in the ethanol–water mixture plays a central role in determining the performance of the hydrogen-transfer reaction. Based on the13 C NMR and ESI–MS results, a possible pathway of the coupled glucose dehydrogenation and CO2 hydrogenation reactions was proposed.
- Ding, Guodong,Su, Ji,Zhang, Cheng,Tang, Kan,Yang, Lisha,Lin, Hongfei
-
-
- Effects of Electrolyte Anions on the Reduction of Carbon Dioxide to Ethylene and Ethanol on Copper (100) and (111) Surfaces
-
The CO2 electroreduction reaction has been investigated on Cu(100) and Cu(111) surfaces in 0.1 m aqueous solutions of KClO4, KCl, KBr, and KI electrolyte. The formation of ethylene and ethanol on these surfaces generally increased as the electrolyte anion was changed from ClO4?→Cl?→Br?→I?. For example, on Cu(100) at ?1.23 V versus RHE, as the electrolyte anion changed from ClO4? to I?, the faradaic efficiency (FE) of ethylene formation increased from 31 to 50 %, FEethanol increased from 7 to 16 %, and the associated current densities increased five- and sevenfold, respectively. A remarkable total FE of up to 74 % for C2 and C3 products was obtained in the presence of KI. Despite surface roughening in the presence of the electrolytes, the Cu(100) electrode still enhanced the formation of C2 compounds better than Cu(111). The favorable reduction of CO2 to C2 products in KI electrolyte was correlated with a higher *CO population on the surface, as shown using linear sweep voltammetry. In situ Raman spectroscopy indicated that the coordination environment of *CO was altered by the used electrolyte anion. Thus, apart from affecting the morphology of the electrode and local pH value, we propose that the anion plays a critical role in enhancing the formation of C2 products by tuning the coordination environment of adsorbed *CO, which gives rise to more efficient C?C coupling.
- Huang, Yun,Ong, Cheng Wai,Yeo, Boon Siang
-
p. 3299 - 3306
(2018/08/11)
-
- Dynamic Changes in the Structure, Chemical State and Catalytic Selectivity of Cu Nanocubes during CO2 Electroreduction: Size and Support Effects
-
In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, chemical state, and reactivity of size- and shape-controlled ligand-free Cu nanocubes during CO2 electroreduction (
- Grosse, Philipp,Gao, Dunfeng,Scholten, Fabian,Sinev, Ilya,Mistry, Hemma,Roldan Cuenya, Beatriz
-
supporting information
p. 6192 - 6197
(2018/04/30)
-
- Systematic variation of the optical bandgap in titanium based isoreticular metal-organic frameworks for photocatalytic reduction of CO2 under blue light
-
A series of metal-organic frameworks isoreticular to MIL-125-NH2 were prepared, where the 2-amino-terephthalate organic links feature N-alkyl groups of increasing chain length (from methyl to heptyl) and varying connectivity (primary and secondary). The prepared materials display reduced optical bandgaps correlated with the inductive donor ability of the alkyl substituent as well as high photocatalytic activity towards the reduction of carbon dioxide under blue illumination operating over 120 h. Secondary N-alkyl substitution (isopropyl, cyclopentyl and cyclohexyl) exhibits larger apparent quantum yields than the primary N-alkyl analogs directly related to their longer lived excited-state lifetime. In particular, MIL-125-NHCyp (Cyp = cyclopentyl) exhibits a small bandgap (Eg = 2.30 eV), a long-lived excited-state (τ = 68.8 ns) and a larger apparent quantum yield (Φapp = 1.80%) compared to the parent MIL-125-NH2 (Eg = 2.56 eV, Φapp = 0.31%, τ = 12.8 ns), making it a promising candidate for the next generation of photocatalysts for solar fuel production based on earth-abundant elements.
- Logan, Matthew W.,Ayad, Suliman,Adamson, Jeremy D.,Dilbeck, Tristan,Hanson, Kenneth,Uribe-Romo, Fernando J.
-
supporting information
p. 11854 - 11863
(2017/07/10)
-
- Role of the Adsorbed Oxygen Species in the Selective Electrochemical Reduction of CO2 to Alcohols and Carbonyls on Copper Electrodes
-
The electrochemical reduction of CO2 into fuels has gained significant attention recently as source of renewable carbon-based fuels. The unique high selectivity of copper in the electrochemical reduction of CO2 to hydrocarbons has called much interest in discovering its mechanism. In order to provide significant information about the role of oxygen in the electrochemical reduction of CO2 on Cu electrodes, the conditions of the surface structure and the composition of the Cu single crystal electrodes were controlled over time. This was achieved using pulsed voltammetry, since the pulse sequence can be programmed to guarantee reproducible initial conditions for the reaction at every fraction of time and at a given frequency. In contrast to the selectivity of CO2 reduction using cyclic voltammetry and chronoamperometric methods, a large selection of oxygenated hydrocarbons was found under alternating voltage conditions. Product selectivity towards the formation of oxygenated hydrocarbon was associated to the coverage of oxygen species, which is surface-structure- and potential-dependent.
- Le Duff, Cécile S.,Lawrence, Matthew J.,Rodriguez, Paramaconi
-
p. 12919 - 12924
(2017/10/07)
-
- Solvothermally-Prepared Cu2O Electrocatalysts for CO2 Reduction with Tunable Selectivity by the Introduction of p-Block Elements
-
The electroreduction of CO2 to fuels and chemicals is an attractive strategy for the valorization of CO2 emissions. In this study, a Cu2O electrocatalyst prepared by a simple and potentially scalable solvothermal route effectively targeted CO evolution at low-to-moderate overpotentials [with a current efficiency for CO (CECO) of ca. 60 % after 12 h at ?0.6 V vs. reversible hydrogen electrode, RHE], and its selectivity was tuned by the introduction of p-block elements (In, Sn, Ga, Al) into the catalyst. SEM, HRTEM, and voltammetric analyses revealed that the Cu2O catalyst undergoes extensive surface restructuring (favorable for CO evolution) under the reaction conditions. The modification of Cu2O with Sn and In further enhanced the current efficiency (CE) for CO (ca. 75 % after 12 h at ?0.6 V). In contrast, the introduction of Al altered the selectivity profile of the catalyst significantly, decreasing the selectivity toward CO but promoting the reduction of CO2 to ethylene (CE≈7 %), n-propanol, and ethanol (CE≈2 % each) at ?0.8 V vs. RHE. This result is related to a decreased reducibility of Al-doped Cu2O that might preserve Cu+ species (favorable for C2H4 production) under the reaction conditions, which is supported by XRD, X-ray photoelectron spectroscopy, and H2 temperature-programmed reduction observations.
- Larrazábal, Gastón O.,Martín, Antonio J.,Krumeich, Frank,Hauert, Roland,Pérez-Ramírez, Javier
-
p. 1255 - 1265
(2017/03/29)
-
- Promoter Effects of Alkali Metal Cations on the Electrochemical Reduction of Carbon Dioxide
-
The electrochemical reduction of CO2 is known to be influenced by the identity of the alkali metal cation in the electrolyte; however, a satisfactory explanation for this phenomenon has not been developed. Here we present the results of experimental and theoretical studies aimed at elucidating the effects of electrolyte cation size on the intrinsic activity and selectivity of metal catalysts for the reduction of CO2. Experiments were conducted under conditions where the influence of electrolyte polarization is minimal in order to show that cation size affects the intrinsic rates of formation of certain reaction products, most notably for HCOO-, C2H4, and C2H5OH over Cu(100)- and Cu(111)-oriented thin films, and for CO and HCOO- over polycrystalline Ag and Sn. Interpretation of the findings for CO2 reduction was informed by studies of the reduction of glyoxal and CO, key intermediates along the reaction pathway to final products. Density functional theory calculations show that the alkali metal cations influence the distribution of products formed as a consequence of electrostatic interactions between solvated cations present at the outer Helmholtz plane and adsorbed species having large dipole moments. The observed trends in activity with cation size are attributed to an increase in the concentration of cations at the outer Helmholtz plane with increasing cation size.
- Resasco, Joaquin,Chen, Leanne D.,Clark, Ezra,Tsai, Charlie,Hahn, Christopher,Jaramillo, Thomas F.,Chan, Karen,Bell, Alexis T.
-
p. 11277 - 11287
(2017/08/22)
-
- Selective Electrochemical Reduction of Carbon Dioxide to Ethylene and Ethanol on Copper(I) oxide catalysts
-
The selective electroreduction of carbon dioxide to C2 compounds (ethylene and ethanol) on copper(I) oxide films has been investigated at various electrochemical potentials. Aqueous 0.1 M KHCO3 was used as electrolyte. A remarkable finding is that the faradic yields of ethylene and ethanol can be systematically tuned by changing the thickness of the deposited overlayers. Films 1.7-3.6 μm thick exhibited the best selectivity for these C2 compounds at -0.99 V vs RHE, with faradic efficiencies (FE) of 34-39% for ethylene and 9-16% for ethanol. Less than 1% methane was formed. A high C2H4/CH4 products' ratio of up to ~100 could be achieved. Scanning electron microscopy, X-ray diffraction, and in situ Raman spectroscopy revealed that the Cu2O films reduced rapidly and remained as metallic Cu0 particles during the CO2 reduction. The selectivity trends exhibited by the catalysts during CO2 reduction in phosphate buffer, and KHCO3 electrolytes suggest that an increase in local pH at the surface of the electrode is not the only factor in enhancing the formation of C2 products. An optimized surface population of edges and steps on the catalyst is also necessary to facilitate the dissociation of CO2 and the dimerization of the pertinent CHxO intermediates to ethylene and ethanol.
- Ren, Dan,Deng, Yilin,Handoko, Albertus Denny,Chen, Chung Shou,Malkhandi, Souradip,Yeo, Boon Siang
-
p. 2814 - 2821
(2015/05/20)
-
- Electrocatalytic production of C3-C4 compounds by conversion of CO2 on a chloride-induced Bi-phasic Cu2O-Cu catalyst
-
Electrocatalytic conversion of carbon dioxide (CO2) has recently received considerable attention as one of the most feasible CO2 utilization techniques. In particular, copper and copper-derived catalysts have exhibited the ability to produce a number of organic molecules from CO2. Herein, we report a chloride (Cl)-induced bi-phasic cuprous oxide (Cu2O) and metallic copper (Cu) electrode (Cu2OCl) as an efficient catalyst for the formation of high-carbon organic molecules by CO2 conversion, and identify the origin of electroselectivity toward the formation of high-carbon organic compounds. The Cu2OCl electrocatalyst results in the preferential formation of multi-carbon fuels, including n-propanol and n-butane C3-C4 compounds. We propose that the remarkable electrocatalytic conversion behavior is due to the favorable affinity between the reaction intermediates and the catalytic surface. Cl-induced bi-phasic Cu2O-Cu shows remarkable catalytic ability for CO2 conversion toward high-carbon-number compounds. The oxidized Cu phase allows reaction intermediates to stay for a longer time on the surface, and consequently leads to formation of larger molecules.
- Lee, Seunghwa,Kim, Dahee,Lee, Jaeyoung
-
supporting information
p. 14701 - 14705
(2016/02/09)
-
- Solvolytic Behavior of Aliphatic Carboxylates
-
The leaving group abilities (nucleofugalities) of a series of aliphatic carboxylates have been obtained by determining the nucleofuge-specific parameters (Nf and sf) from solvolysis rate constants of X,Y-substituted benzhydryl carboxylates in a series of aqueous ethanol mixtures by applyication of the linear free energy relationship (LFER) equation: log k = sf (Ef + Nf). These values can be employed to compare reactivities of carboxylates with those of other leaving groups previously included in the nucleofugality scale, and also to estimate the solvolysis rates of various carboxylates. It is confirmed that the inductive effect is the most important variable governing the reactivities of halogenated carboxylates in solution. Moreover, both the Hammett correlation and the solvolytic activation parameters have revealed a strong influence of the inductive effect on the nucleofugality of alkyl-substituted carboxylates. The reaction constants (sf) indicate that carboxylate substrates with weaker leaving groups solvolyze via later, more carbocation-like, transition states, which is in accord with the Hammond postulate. In addition, due to the weaker demand for solvation of transition states that produce more strongly stabilized benzhydrylium ions, in which more efficient charge delocalization occurs, the reaction constants (sf) obtained with most of the leaving groups investigated here increase as the polarity of the solvent decreases.
- Matic, Mirela,Denegri, Bernard,Kronja, Olga
-
supporting information
p. 1477 - 1486
(2015/10/05)
-
- Electrocatalytic and photocatalytic conversion of CO2 to methanol using ruthenium complexes with internal pyridyl cocatalysts
-
The ruthenium complexes [Ru(phen)2(ptpbα)]2+ (Ruα) and [Ru(phen)2(ptpbβ)]2+ (Ruβ), where phen =1,10-phenanthroline; ptpbα = pyrido[2′,3′:5,6] pyrazino[2,3-f][1,10]phenanthroline; ptpbβ = pyrido[3′,4′:5,6] pyrazino[2,3-f][1,10]phenanthroline, are shown as electrocatalysts and photocatalysts for CO2 reduction to formate, formaldehyde, and methanol. Photochemical activity of both complexes is lost in water but is retained in 1 M H2O in DMF. Controlled current electrolysis of a solution of Ruβ in CO2 saturated DMF:H2O (1 M) yields predominantly methanol over a 6 h period at ~ -0.60 V versus Ag/AgCl, with traces of formaldehyde. After this time, the potential jumped to -1.15 V producing both methanol and CO as products. Irradiation of Ruβ in a solution of DMF:H2O (1 M) containing 0.2 M TEA (as the sacrificial reductant) yields methanol, formaldehyde, and formate. Identifications of all of the relevant redox and protonated states of the respective complexes were obtained by a combination of voltammetry and differential reflectance measurements. Spectroelectrochemistry was particularly useful to probe the photochemical and electrochemical reduction mechanisms of both complexes as well as the complexes speciation in the absence and presence of CO2.
- Boston, David J.,Pachon, Yeimi M. Franco,Lezna, Reynaldo O.,De Tacconi,MacDonnell, Frederick M.
-
p. 6544 - 6553
(2014/07/22)
-
- A high-valent heterobimetallic [CuIII(μ-O)2Ni III]2+ core with nucleophilic oxo groups
-
Cores and effect: Unlike homobimetallic analogues, the heterobimetallic CuNi bis(μ-oxo) diamond core has nucleophilic oxo groups. A similar heterobimetallic core may, therefore, act as a viable intermediate during the deformylation of fatty aldehydes by cyanobacterial aldehyde decarbonylase. Copyright
- Kundu, Subrata,Pfaff, Florian Felix,Miceli, Enrico,Zaharieva, Ivelina,Herwig, Christian,Yao, Shenglai,Farquhar, Erik R.,Kuhlmann, Uwe,Bill, Eckhard,Hildebrandt, Peter,Dau, Holger,Driess, Matthias,Limberg, Christian,Ray, Kallol
-
supporting information
p. 5622 - 5626
(2013/06/27)
-
- Effect of water during the quantitation of formate in photocatalytic studies on CO2 reduction in dimethylformamide
-
The effect of the water concentration on the quantitation of formate from dimethylformamide in the presence of electron-donating bases using ion chromatography is reported. This observation has important implications in the area of the photocatalytic reduction of CO2, where formate levels are often used to calculate catalyst turnover numbers.
- Paul, Avishek,Connolly, Damian,Schulz, Martin,Pryce, Mary T.,Vos, Johannes G.
-
body text
p. 1977 - 1979
(2012/05/05)
-
- Oxidation of ethanolamines by sodium N-bromobenzenesulfonamide in alkaline buffer medium: A kinetic and mechanistic study
-
The kinetics of oxidation of ethanolamines, monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA), by sodium N-bromobenzenesulfonamide or bromamine-B (BAB) in alkaline buffer medium (pH 8.7-12.2) has been studied at 40°C. The three reactions follow identical kinetics with first-order in [oxidant] and fractional-order each in [substrate] and [OH-]. Under comparable experimental conditions, the rate of oxidation increases in the order: DEA > TEA > MEA. The added reaction product, benzenesulfonamide, retards the reaction rate. The addition of halide ions and the variation of ionic strength of the medium have no significant effect on the rate. The dielectric effect is negative. The solvent isotope effect k′(H2O)/k′(D2O) ≈ 0.92. Activation parameters for the composite reaction and for the rate-limiting step were computed from the Eyring plots, Michaelis-Menten type of kinetics is observed. The formation and decomposition constants of ethanolamine-BAB complexes are evaluated. An isokinetic relationship is observed with β = 430 K indicating that enthalpy factors control the rate. For each substrate, a mechanism consistent with the kinetic data has been proposed.
- Puttaswamy,Vaz, Nirmala,Made Gowda
-
p. 480 - 490
(2007/10/03)
-