- Utilizing hydrogen underpotential deposition in CO reduction for highly selective formaldehyde production under ambient conditions
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Formaldehyde is an essential building block for hundreds of chemicals and a promising liquid organic hydrogen carrier (LOHC), yet its indirect energy-intensive synthesis process prohibits it from playing a more significant role. Here we report a direct CO reduction to formaldehyde (CORTF) process that utilizes hydrogen underpotential deposition to overcome the thermodynamic barrier and the scaling relationship restriction. This is the first time that this reaction has been realized under ambient conditions. Using molybdenum phosphide as a catalyst, formaldehyde was produced with nearly a 100% faradaic efficiency in aqueous KOH solution, with its formation rate being one order of magnitude higher compared with the state-of-the-art thermal catalysis approach. Simultaneous tuning of the current density and reaction temperature led to a more selective and productive formaldehyde synthesis, indicating the electrochemical and thermal duality of this reaction. DFT calculations revealed that the desorption of the ?H2CO intermediate likely served as the rate-limiting step, and the participation of H2O made the reaction thermodynamically favorable. Furthermore, a full-cell reaction set-up was demonstrated with CO hydrogenation to HCHO achieved without any energy input, which fully realized the spontaneous potential of the reaction. Our study shows the feasibility of combining thermal and electrochemical approaches for realizing the thermodynamics and for scaling relationship-confined reactions, which could serve as a new strategy in future reaction design.
- Bentalib, Abdulaziz,Pan, Yanbo,Peng, Zhenmeng,Shen, Xiaochen,Wu, Dezhen,Yao, Libo
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- Molybdenum phosphide (MoP) with dual active sites for the degradation of diclofenac in Fenton-like system
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The leaching and non-recoverability of mental ions have always limited the practical application of Fenton-like processes. For the first time, we synthesized molybdenum phosphide (MoP) with dual active sites for the degradation of diclofenac (DCF) in the Fenton-like process. The DCF degradation rate constant (k) of MoP + H2O2 process was calculated to be 0.13 min-1 within 40 min, indicating a highly efficient catalytic ability of MoP. In addition, this catalyst exhibits a stable structure and good activity, which could apply in a broad pH range, different ions solution and real wastewater condition. Accordingly, this efficient catalytic capability may be attributed to the presence of the metal sites Moδ+ and the electron-rich sites Pδ? in MoP, which could induce the generation of hydroxyl radical (?OH) and superoxide radical (?O2?) through electron transfer, resulting in the effective removal of DCF. This study provides an idea for the optimization of Fenton-like technologies and environmental remediation.
- Li, Xiuying,Huang, Shuangqiu,Xu, Huaihao,Deng, Yuepeng,Wang, Zhu,Liu, Zhao-Qing
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- A new approach to the synthesis of molybdenum phosphide via internal oxidation and reduction route
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A new method for the preparation of molybdenum phosphide was reported. Dispersed MoP with lamellar morphology was obtained from the decomposition of a mixed-salt precursor containing (NH4)4Mo7O24·2H2O
- Yao,Wang, Li,Dong, Haitao
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- Phosphorization-derived MoP@MoO3-x nanowires for selective photocatalytic oxidation of benzyl alcohol to benzaldehyde
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The selective oxidation of small molecules to high-value-added products is regarded as a promising approach to alleviating the worldwide energy crisis. In this work, heterogenous non-noble-metal molybdenum(III) phosphide (MoP) catalysts were anchored onto MoO3?x nanowires (MoP@MoO3?x) via a facile phosphorization method using various amounts of phosphorus precursor. Because of the combined attributes of the MoP and the MoO3?x nanowires, the novel MoP@MoO3?x nanowire catalysts not only provide more active sites but also enhance electron–hole separation efficiency. The results show that the selective transformation of benzyl alcohol to benzaldehyde was achieved with 67% selectivity. A comprehensive study including field-emission transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, Brunauer–Emmett–Teller analysis, X-ray diffraction analysis, UV–vis diffuse reflectance spectrum, electron-spin resonance, photocurrent measurements, electrochemical impedance spectroscopy, and density functional theory (DFT) computations was conducted. The selective photocatalytic oxidation results and the DFT calculations indicate that the MoP particles anchored onto the MoO3?x substrate display an important role in enhancing the selective photocatalytic oxidation of benzyl alcohol.
- Zhang, Yifan,Park, Soo-Jin
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- Binary and ternary transition-metal phosphides as HDN catalysts
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Transition-metal phosphides (Co2P, Ni2P, MoP, WP, CoMoP, NiMoP) were prepared by reducing metal oxide/phosphate precursors in a flow of H2. The solids obtained were tested in the hydrodenitrogenation of o-propylaniline at 643 K and 3 MPa. All the catalysts were active, with product selectivities resembling those of sulfidic catalysts. The influence of H2S on the activity and selectivities was tested and is discussed with regard to a possible surface modification. Based on the surface area of each catalyst, we estimated the relative intrinsic activities of the different phosphides. According to this estimation, MoP was intrinsically the most active catalyst.
- Stinner,Prins,Weber, Thomas
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- Physical and chemical properties of MoP, Ni2P, and MoNiP hydrodesulfurization catalysts: Time-resolved X-ray diffraction, density functional, and hydrodesulfurization activity studies
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Fuels derived from petroleum contribute approximately one-third to one-half of the world's energy supply and are utilized for transportation and to heat buildings. More stringent environmental regulations stress the need to develop a new generation of HDS catalysts that result in the ultimate goal of clean-burning fuels. Synchrotron-based time-resolved XRD was utilized to investigate in situ the crystalline phases present during the preparation of bulk and silica-supported MoP, Ni2P, and MoNiP by reduction of oxidic precursors in hydrogen. The formation of the metal phosphides occurred at 600°-800°C. Since the common species in all the cases were phosphate-type groups, their reduction by hydrogen was the final and determining step in the formation of Ni2P, MoP, and MoNiP. Silica-stabilized phosphide phases were observed during the synthesis of Ni2P/SiO2 and MoP/SiO2. α-Ni2P2O7 could be utilized as an oxidic precursor for the synthesis of bulk Ni2P via reduction with hydrogen. Ni-P and Mo-P bonds in the compounds had a small degree of ionic character. For Ni2P, MoS2, and MoP, a correlation was observed between the electronic properties of the metal cations and their HDS activities as silica-supported catalysts. A MoNiP/SiO2 catalyst was much less active than either MoP/SiO2 or Ni2P/SiO2 catalysts.
- Rodriguez, Jose A.,Kim, Jae-Yong,Hanson, Jonathan C.,Sawhill, Stephanie J.,Bussell, Mark E.
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- Reduction of sodium cyclotriphosphate by metallic molybdenum
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The products of the reaction between sodium cyclotriphosphate and powder Mo in vacuum at temperatures up to 1000°C were characterized by x-ray diffraction and 31P nuclear magnetic resonance. Above 650-700°C, the reaction yields MoP and amorphous sodium phosphates (orthophosphate, pyrophosphate, and cyclotetraphosphate) containing Mo in the oxidation state 5+. At the Mo content ensuring the largest percentage of sodium cyclotetraphosphate in the reaction products, these also contain a small amount of elemental phosphorus.
- Aueshov,Levchenko,Eskibaeva,Shustikova,Sinyaev
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- Synthesis, characterization, and hydrodesulfurization properties of silica-supported molybdenum phosphide catalysts
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Silica-supported molybdenum phosphide (MoP/SiO2) catalysts have been prepared and characterized by X-ray diffraction (XRD), pulsed chemisorption (CO and O2), scanning and transmission electron microscopy (SEM and TEM, respectively), and X-ray photo-electron spectroscopy (XPS). XRD and TEM analysis of MoP/SiO2 catalysts confirmed the presence of MoP crystallites dispersed on the surface of the silica support, while SEM energy dispersive X-ray microanalysis indicated the bulk composition of the supported MoP particles to be 12.7 atom% Mo and 14.1 atom% P. XPS analysis of a passivated 25 wt% MoP/SiO2 catalyst indicated the presence of two kinds of Mo species as well as phosphide and phosphate species at the catalyst surface. Thiophene hydrodesulfurization (HDS) activities were measured for 15 and 25 wt% MoP/SiO2 catalysts, and for a sulfided Mo/SiO2 catalyst with a Mo loading similar to that of the lower loading MoP catalyst. The 15 wt% MoP/SiO2 catalyst, when pretreated only by degassing in flowing He, was nearly four times more active than the sulfided Mo/SiO2 catalyst after 150 h on-stream. Following an initial decline in HDS activity during the first 3 h of measurement, the MoP/SiO2 catalyst displayed an unusual trend of HDS activity that increased monotonically as a function of time on-stream.
- Phillips, Diana C.,Sawhill, Stephanie J.,Self, Randy,Bussell, Mark E.
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- A novel and facile synthetic route to MMo (M = Ni or Co) bimetallic phosphides
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A novel and facile route to bimetallic molybdenum phosphides was described. Both NiMoP and CoMoP phosphides were successfully prepared by a hexamethylenetetramine (HMT) route. Mixed-salt precursors containing HMT, M-HMT (M = Ni, Co or Mo) complexes, MMo-HMT (M = Ni or Co) complexes and P-containing species can be directly converted to bimetallic molybdenum phosphides under a flow of Ar at 800 °C. It was proposed that the bimetallic phosphides were formed via two possible reaction pathways: (i) MMo-HMT complexes/P→MMoP (M = Ni or Co) and (ii) M-HMT (M = Ni, Co or Mo) complexes/P→M2P/MoP→MMoP (M = Ni or Co). Additionally, it was found that the dispersions and surface areas of NiMoP and CoMoP prepared by HMT route were higher than those of corresponding bimetallic phosphides prepared by traditional H2 reduction method.
- Yao, Zhiwei,Dong, Meijun,Shi, Yan,Sun, Yue,Liu, Qingyou
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- A novel synthetic route to transition metal phosphide nanoparticles
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A novel synthetic route was developed to prepare nano-sized and well-dispersed phosphides of transition metals (Mo, Ni, and Co) from their corresponding oxide precursors. The current approach produced metal phosphides in dimethyl ether (DME) using the rapid heating reduction (RHR) method. The synthesis of phosphides in DME was interesting, since the composition of gas-phase products was predominantly H2, CO and CH4 with a minor amount of CO2 but without H2O. Based on XRD and MS results, the formation mechanism of the phosphides was proposed. The overall synthesis process cannot simply be regarded as the reduction of an oxide precursor and the decomposition of DME. The product distribution should be ascribed to a combination of other catalytic reactions. In addition, it is noteworthy that compared with the traditional method, viz. temperature-programmed reduction in H2 (TPR-H2), the present method used a higher heating rate to shorten the reaction time and can yield more finely dispersed metal phosphide nanoparticles. The good dispersion of phosphide nanoparticles is probably achieved due to the fact that no H2O was released in the RHR-DME process, which can avoid strong hydrothermal sintering.
- Yao, Zhiwei,Li, Meng,Wang, Xiang,Qiao, Xue,Zhu, Jiang,Zhao, Yu,Wang, Guanzhang,Yin, Jingzhou,Wang, Haiyan
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- Mechanical mixtures of metal oxides and phosphorus pentoxide as novel precursors for the synthesis of transition-metal phosphides
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This study presents a new type of precursor, mechanical mixtures of metal oxides (MOs) and phosphorus pentoxide (P2O5) are used to synthesize Ni2P, Co2P and MoP phosphides by the H2 reduction method. In addition, this is first report of common solid-state P2O5 being used as a P source for the synthesis of metal phosphides. The traditional precursors are usually prepared via a complicated preparation procedure involving dissolution, drying and calcination steps. However, these novel MOs/P2O5 precursors can be obtained only by simple mechanical mixing of the starting materials. Furthermore, unlike the direct transformation from amorphous phases to phosphides, various specific intermediates were involved in the transformation from MOs/P2O5 to phosphides. It is worthy to note that the dispersions of Ni2P, Co2P and MoP obtained from MOs/P2O5 precursors were superior to those of the corresponding phosphides prepared from the abovementioned traditional precursors. It is suggested that the morphology of the as-prepared metal phosphides might be inherited from the corresponding MOs. Based on the results of XRD, XPS, SEM and TEM, the formation pathway of phosphides can be defined as MOs/P2O5 precursors → complex intermediates (metals, metal phosphates and metal oxide-phosphates) → metal phosphides.
- Guo, Lijuan,Zhao, Yu,Yao, Zhiwei
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- Molybdenum phosphide, a new hydrazine decomposition catalyst: Microcalorimetry and FTIR studies
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Unsupported and Al2O3-supported molybdenum phosphides (MoP) were tested as catalysts for the decomposition of hydrazine (N2H4), in comparison with previously studied Mo2N catalysts. The results showed that the activity increased with MoP loading on the MoP/Al2O3 catalysts and that the supported MoP catalysts were more stable during hydrazine decomposition compared with the supported Mo2N catalysts. FTIR results indicated that N2H4 decomposed on the Mo sites on the MoP, similar to the case of Mo2N. FTIR and microcalorimetric adsorption measurements showed that NH3 was adsorbed only moderately on the MoP catalyst, giving it better catalytic stability than the Mo2N, for which strong adsorption of NH3 blocked the active sites and led to a sharp decrease in activity.
- Cheng, Ruihua,Shu, Yuying,Zheng, Mingyuan,Li, Lin,Sun, Jun,Wang, Xiaodong,Zhang, Tao
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- On the surface sites of MoP/SiO2 catalyst under sulfiding conditions: IR spectroscopy and catalytic reactivity studies
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In recent decades, there has been worldwide interest in the development of new technologies for the production of clean fuels because of the more stringent environmental legislation and the increase of low-quality stocks. The surface sites of MoP/SiO2 catalysts and their evolution under sulfiding conditions were characterized by IR spectroscopy using CO as probe molecule. The HDS activities of thiophene were measured on the MoP/SiO2 catalyst that was subjected to different sulfidation and reactivation pretreatments. The surface of MoP/SiO2 was gradually sulfided in HDS reactions. Although the surface of a MoP/SiO2 catalyst became partially sulfided, the HDS activity tests show that MoP/SiO2 was fairly stable in the initial stage of the HDS reaction, providing further proof that molybdenum phosphide is a promising catalytic material for industrial HDS reactions. Two kinds of surface sulfur species were formed on the sulfided catalyst, i.e., reversibly and irreversibly bonded S species. The MoP/SiO2 catalyst remained stable in the HDS of thiophene because most sulfur species formed under HDS conditions were reversibly bonded on the catalyst surface. A detrimental effect of presulfidation on the HDS activity was observed for the MoP/SiO2 catalyst treated by H2S/H2 at > 623 K. The irreversibly sulfided catalyst could be completely regenerated by an oxidation and a subsequent reduction under mild conditions.
- Wu, Zili,Sun, Fuxia,Wu, Weicheng,Feng, Zhaochi,Liang, Changhai,Wei, Zhaobin,Li, Can
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- Preparation of high-performance MoP hydrodesulfurization catalysts via a sulfidation-reduction procedure
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MoP/MCM-41 was prepared from its oxidic precursors by sulfidation at 400 °C for 3 h using 10% H2S/H2, followed by temperature-programed reduction in H2. The resulting catalyst, MoP/MCM-41(SR), showed considerably a higher
- Teng, Yang,Wang, Anjie,Li, Xiang,Xie, Jianguo,Wang, Yao,Hu, Yongkang
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- MoP Nanoparticles Supported on Indium-Doped Porous Carbon: Outstanding Catalysts for Highly Efficient CO2 Electroreduction
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Electrochemical reduction of CO2 into value-added product is an interesting area. MoP nanoparticles supported on porous carbon were synthesized using metal–organic frameworks as the carbon precursor, and initial work on CO2 electroreduction using the MoP-based catalyst were carried out. It was discovered that MoP nanoparticles supported on In-doped porous carbon had outstanding performance for CO2 reduction to formic acid. The Faradaic efficiency and current density could reach 96.5 % and 43.8 mA cm?2, respectively, when using ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate as the supporting electrolyte. The current density is higher than those reported up to date with very high Faradaic efficiency. The MoP nanoparticles and the doped In2O3 cooperated very well in catalyzing the CO2 electroreduction.
- Sun, Xiaofu,Lu, Lu,Zhu, Qinggong,Wu, Congyi,Yang, Dexin,Chen, Chunjun,Han, Buxing
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- Porous Molybdenum Phosphide Nano-Octahedrons Derived from Confined Phosphorization in UIO-66 for Efficient Hydrogen Evolution
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Herein, a series of porous nano-structured carbocatalysts have been fused and decorated by Mo-based composites, such as Mo2C, MoN, and MoP, to form a hybrid structures. Using the open porosity derived from the pyrolysis of metal–organic frameworks (MOFs), the highly dispersive MoO2small nanoparticles can be deposited in porous carbon by chemical vapor deposition (CVD). Undergoing different treatments of carbonization, nitridation, and phosphorization, the Mo2C-, MoN-, and MoP-decorated carbocatalysts can be selectively prepared with un-changed morphology. Among these Mo-based composites, the MoP@Porous carbon (MoP@PC) composites exhibited remarkable catalytic activity for the hydrogen evolution reaction (HER) in 0.5 m H2SO4aqueous solution versus MoO2@PC, Mo2C@PC, and MoN@PC. This study gives a promising family of multifunctional lab-on-a-particle architectures which shed light on energy conversion and fuel-cell catalysis.
- Yang, Jian,Zhang, Fengjun,Wang, Xin,He, Dongsheng,Wu, Geng,Yang, Qinghua,Hong, Xun,Wu, Yuen,Li, Yadong
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- Hydrodesulfurization of dibenzothiophene and its hydrogenated intermediates over bulk MoP
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The hydrodesulfurization (HDS) of dibenzothiophene (DBT) and its hydrogenated intermediates 1,2,3,4-tetrahydro-dibenzothiophene (TH-DBT) and 1,2,3,4,4a,9b-hexahydro-dibenzothiophene (HH-DBT) over a bulk MoP catalyst was studied at 340 °C and 4 MPa both in the presence and absence of piperidine. The results indicated that sulfur was incorporated on the surface of MoP during HDS reactions, probably leading to the formation of new active sites, which possessed higher direct desulfurization (DDS) activity than the fresh MoP. The hydrogenation pathway and DDS pathway played an equally important role in the HDS of DBT. The desulfurization of TH-DBT was much faster than that of DBT, whereas HH-DBT mainly desulfurized by dehydrogenation to TH-DBT and subsequent desulfurization of TH-DBT. Piperidine decreased the rates of all reactions, but that of hydrogenation more than of desulfurization. It not only competed with the sulfur-containing molecules for adsorption on the active sites but also slowed down the sulfidation of MoP surface.
- Bai, Jin,Li, Xiang,Wang, Anjie,Prins, Roel,Wang, Yao
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- Alumina-supported molybdenum phosphide hydroprocessing catalysts
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Alumina-supported molybdenum phosphide hydroprocessing catalysts, MoP/γ-Al2O3, with 3.5-39 wt % were prepared by TPR of alumina-supported molybdenum phosphate precursors. Effects of loading, reduction temperature, and heating rate on the catalysts were studied. The MoP/γ-Al2O3 catalysts performed well in hydroprocessing of a simulated distillate containing dibenzothiophene and quinoline at conditions representative of industrial hydroprocessing (643 K and 3.1 MPa). For the 13 wt % sample, the HDS conversion was 57% and HDN conversion 62%. Catalytic activity was generally independent of the amount of MoP deposited on the alumina surface, independent of the presence of X-ray visible molybdenum phases, and was associated with a relatively high temperature reduction peak found at all loading levels of MoP/Al2O3 but not in bulk MoP. The high-temperature peak resulted in highly dispersed MoP, which was responsible for the bulk of the CO titration sites and the catalytic activity. The amount of hydrogenated quinoline products was stable near 30%, consistent with equilibration between quinoline and 1,2,3,4-tetrahydroquinoline.
- Clark, Paul A.,Oyama, S. Ted
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- Characterization of silica-supported molybdenum and tungsten phosphide hydroprocessing catalysts by 31P nuclear magnetic resonance spectroscopy
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Silica-supported molybdenum phosphide, MoP/SiO2, and tungsten phosphide, WP/SiO2, were prepared and characterized for their catalytic activity in hydrodenitrogenation (HDN) and hydrodesulfurization (HDS). The silica-supported phosphides were tested in the simultaneous hydroprocessing of quinoline and dibenzothiophene at 3.1 MPa and 643 K and were compared to a MoS2/SiO2 sample. The supported phosphides had superior HDN and lower HDS activity compared to the sulfide under these conditions. The conversion levels of MoP/SiO2 were similar to those of bulk MoP, while the WP/SiO2 was somewhat less active than its bulk WP counterpart. However, when compared on a CO uptake basis, the bulk materials had a clear performance advantage. Solid state nuclear magnetic resonance measurements indicated 31P shifts from 85% H3PO4 of 255 ppm for WP and 214 ppm for MoP. Comparison of freshly prepared and passivated samples indicated that the supported phosphides were susceptible to surface oxidation on exposure to the atmosphere as a result of their small particle size.
- Clark,Wang,Oyama
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- A new metal-organic open framework enabling facile synthesis of carbon encapsulated transition metal phosphide/sulfide nanoparticle electrocatalysts
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Engineering 3d to 5d nonprecious transition metal electrocatalysts to demonstrate both high activity and superior durability for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), which would be ideal for enabling low-cost hydrogen production from water splitting, remains a serious challenge. Herein, we report the rational design and experimental realization of a new metal-organic open framework (MOF) to enable a facile and scalable synthesis of transition metal phosphide (TMP) and sulfide (TMS) composite nanoparticle electrocatalysts encapsulated by heteroatom-doped carbon (TMP/C and TMS/C) as bifunctional electrocatalysts for water splitting. Using this new MOF, we synthesized NiP/NiFeP/C and MoWS/MoP/C composite nanoparticle electrocatalysts that exhibited outstanding electrocatalytic activities and durability that are among the higher values reported in the literature for HER and OER electrocatalysts. A two-electrode water-splitting device using our bifunctional NiP/NiFeP/C catalyst reached 10 mA cm-2 at a cell voltage of 1.53 V and 100 mA cm-2 at 1.68 V in 1.0 M KOH. The device showed excellent stability for overall water splitting with almost 98% retention of its initial current of 100 mA cm-2 for over 20 h. Our results demonstrate the versatility of the new MOF to synthesize highly active and stable TM-based electrocatalysts for water splitting.
- Weng, Baicheng,Wang, Xiaoming,Grice, Corey R.,Xu, Fenghua,Yan, Yanfa
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- A novel synthetic approach to synthesizing bulk and supported metal phosphides
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This paper presents a novel synthetic approach to synthesizing metal phosphides. Both bulk and supported Ni2P, Cu3P, MoP, and InP were synthesized by thermal decomposition of their metal oxide and hypophosphite precursors. Mechanistic studies of Ni2P were carried out using a separated-bed tube reactor, and the result indicates that NiO is reduced by PH3 (produced from decomposition of NaH2PO2) at 300 °C. Ni2P hollow spheres were successfully synthesized by this method, which indicates that it is possible to synthesize metal phosphides with special morphology by using metal oxides with special morphology as precursors.
- Guan, Qingxin,Li, Wei
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- Efficient hydrogenation performance improvement of MoP and Ni2P catalysts by adjusting the electron distribution around Mo and Ni atoms
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MoP and Ni2P catalysts were modified by elements with different electronegativities. Based on this method, two series of catalysts were designed and synthesized: Mo based phosphide catalysts (MoP, Mo8WP9, Mo8CuP9) and Ni based phosphide catalysts (Ni2P, Ni38W2P20). The consistency between synthetized and designed materials was mainly verified by XRD, SEM-EDS, TEM, EXAFS. Then, relative catalyst parameters were further characterized using BET, and CO chemisorption. The hydrogenation properties of verified synthesized catalysts are evaluated by hydrodeoxygenation of methyl palmitate. The activity of the catalysts followed the order: Mo8WP9 > MoP > Mo8CuP9, Ni38W2P20 > Ni2P. In particular, the W modified catalysts (Mo8WP9 and Ni38W2P20) exhibited hydrogenation activities 2.83 and 3.68 times that of MoP and Ni2P, respectively. Further, the product selectivities of different catalysts were analysed detailedly. The C16/C15 molar ratio was increased with the incorporation of W, which represented that the selectivity of the HDO pathway increased. While the C16/C15 molar ratio was decreased with the introduction of Cu, and this suggested that the selectivity of decarbonylation increased. These results indicate that the adjustment of the electron distribution around Mo and Ni atoms could successfully control the hydrogenation properties of catalysts.
- Lu, Mingyue,Zheng, Lirong,Li, Rongguan,Guan, Qingxin,Li, Wei
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- Formation, structure, and HDN activity of unsupported molybdenum phosphide
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Transition metal sulfides are used as catalysts in HDS and HDN. The removal of nitrogen- and sulfur-containing compounds from fuels is essential for NOx and SO2 abatement. To test the idea that phosphate may react with Ni-MoS2 to form a catalyst with (partly) phosphide-like character, a pure MoP was prepared from an aqueous solution of (NH4)6Mo7O24 · 4H2O and (NH4)2HPO4 by precipitation, calcination, and subsequent reduction in H2 at 923 K. The aqueous solutions contained MoO42-, HPO42-, and P2Mo5O236- anions. Pure MoP formed after precipitation and reduction with H2. MoP crystallized in the tungsten carbide structure in which each Mo atom is trigonal-prismatically coordinated by six P atoms. The intrinsic HDN activity of the surface Mo atoms of MoP was nearly six times higher than that of Mo edge atoms in γ-Al2O3-supported MoS2. Their selectivity was comparable to that of an Ni-promoted MoS2 catalyst.
- Stinner,Prins,Weber, Th.
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- Novel synthesis of dispersed molybdenum and nickel phosphides from thermal carbonization of metal- and phosphorus-containing resins
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Dispersed pure phases of MoP and Ni2P nanoparticles supported by carbon were synthesized by carbonization of metal- and phosphorus-containing resins under an inert atmosphere. The solid products and the evolution of gases during the carbonization process were investigated by various techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), N2 adsorption-desorption analysis, and mass spectrometry (MS). The resins underwent two carbonization stages: the low-temperature carbonization stage (x species were further reacted with the carbonization products (C, H2 and CH4) to yield Mo(Ni) phosphide. Note that compared with the traditional H2-temperature-programmed reduction (H2-TPR) method, this novel synthesis route produced a large amount of COx besides H2O, leading to a lower water vapor pressure. In addition, the residual carbon produced from resin can play a role in bonding of nanoparticle aggregation. Therefore, the better dispersions and higher surface areas of the as-prepared phosphide nanoparticles were attributed to the mitigation of hydrothermal sintering and the intimate contact between phosphide nanoparticles and carbon species.
- Yao, Zhiwei,Tong, Jin,Qiao, Xue,Jiang, Jun,Zhao, Yu,Liu, Dongmei,Zhang, Yichi,Wang, Haiyan
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- Structural stability and mutual transformations of molybdenum carbide, nitride and phosphide
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The structural stability and transformations of Mo carbide, nitride and phosphide were investigated under various atmosphere conditions by X-ray diffraction (XRD). The results indicated that the order of structural stability of these Mo-based compounds was as follows: Mo2N 2C 2C and Mo2N can be transformed to MoP, whereas the reverse transformations did not occur. Noticeably, compared with those Mo sources containing oxygen, the use of Mo2C/Mo2N as Mo-source can produce finely dispersed MoP nanoparticles by the temperature-programmed reaction (TPR) method. The result was probably due to the fact that lower-levels H2O generated during synthesis process can avoid strong hydrothermal sintering. The influence of formation energy had been considered and was found to relate to the structural stability and transformations of these Mo-based compounds.
- Yao, Zhiwei,Lai, Zhuangchai,Zhang, Xiaohong,Peng, Feng,Yu, Hao,Wang, Hongjuan
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- Lithium-ion storage in molybdenum phosphides with different crystal structures
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Transition metal phosphides have been receiving a great deal of attention as anode materials for Li-ion batteries due to their novel properties of high theoretical capacity and relatively low polarization. MoP and MoP2 nanoparticles with different crystal structures are synthesized by phosphorization in different stoichiometric proportions, using Mo nanospheres as the precursor produced by the plasma evaporation method. When used as the anode material for Li-ion batteries, the MoP2 electrode delivers a stable capacity of 676.60 mA h g-1 after 300 cycles at a current density of 0.1 A g-1 with obvious discharge/charge plateaus; however, the capacity of the hexagonal MoP electrode is 312.38 mA h g-1. The first-principles calculations illustrate that the di-phosphorus bond of MoP2 is prone to break and the distal P atoms preferentially bind with Li atoms to form Li3P during lithiation, but MoP prefers to form ternary LixMoP. The ex situ X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) of the MoP2 electrode after cycling confirm the conversion reaction for the electrochemical storage of Li-ions.
- Jin, Xiaozhe,Tian, Ruixue,Wu, Aimin,Xiao, Yadan,Dong, Xufeng,Hu, Fangyuan,Huang, Hao
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p. 2225 - 2233
(2020/02/26)
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- Method for preparing hydrocarbyl phenol by catalytic conversion of phenolic compound in presence of molybdenum-based catalyst
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The invention discloses a method for preparing hydrocarbyl phenol by catalytic conversion of a phenolic compound in the presence of a molybdenum-based catalyst. The method comprises mixing a phenoliccompound, a molybdenum-based catalyst and a reaction solvent, adding the mixture into a sealed reactor, feeding gas into the reactor, heating the mixture to 150-350 DEG C, carrying out stirring for areaction for 0.5-2h, then filtering to remove a solid catalyst and carrying out rotary evaporateion to obtain a liquid product. The phenolic compound has a wide source, a cost is low, product alkyl phenol selectivity is high, an added value is high, alcohol or an alcohol-water mixture is used as a reaction solvent, environmental friendliness is realized, pollution is avoided, any inorganic acids and alkalis are avoided in the reaction process, the common environmental pollution problems in the biomass processing technology are solved, the reaction conditions are mild, the process can be carried out at a low temperature, high-efficiency conversion of the reactants can be realized without consuming hydrogen gas and the method is suitable for large-scale industrial trial production.
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Paragraph 0066-0067
(2018/04/02)
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- Effect of citric acid on the synthesis of MoP catalyst for CO2 reforming of CH4
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A new molybdenum phosphide (MoP) catalyst was successfully synthesized for CO2 reforming of CH4 reaction. The catalysts were prepared by temperature-programmed reduction (TPR) of phosphomolybdate precursors which were modified by citric acid (CA) at the molar ratio of MoP:CA = 1: x (x = 0, 1.0, 2.0, 3.0), which were characterized by means of X-ray diffraction(XRD), N2 adsorption-desorption and CO2-TPD techniques. The results showed that the addition of citric acid can affect the catalytic activity and that the MoP catalyst had the highest catalytic activity at 1073 K and X=1. After reduced in H2 flow at 923 K, the activity of the post-reaction catalyst can be well restored, while its structure remains unchanged. In higher temperatures, the samples exhibit good anti-sintering ability and stability.
- Guo, Hui-Rui,Li, Xian-Cai,Yang, Ai-Jun,Yang, Yi-Feng,Yu, Li-Li
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p. 463 - 468
(2016/08/30)
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- Templated-preparation of a three-dimensional molybdenum phosphide sponge as a high performance electrode for hydrogen evolution
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Electrocatalysts play a vital role in electrochemical water-splitting for hydrogen production. Here, we report the preparation of three-dimensional molybdenum phosphide (MoP) as a non-precious-metal electrocatalyst for the hydrogen evolution reaction (HER) by using cheap sponge (polyurethane, PU) as a sacrificial template. The obtained 3D MoP not only has large surface area, but also possesses a porous and channel-rich structure, in which the side walls of the pores are composed of refined nanoparticles. The 3D MoP sponge was used as a bulky and binder-free HER electrode and exhibited excellent catalytic activity in an acidic electrolyte (achieving 10 and 20 mA cm-2 at an overpotential of 105 and 155 mV, respectively). In addition, this novel bulky HER electrode showed a relatively small Tafel slope of 126 mV dec-1, a high exchange current density of 3.052 mA cm-2, and a faradaic efficiency of nearly 100%. Furthermore, this bulky electrode revealed high tolerance and durability both under acidic and basic conditions, maintaining 96% and 93% of its initial catalytic activity after continuous testing for 60000 s. Thus, our work paves a feasible way of fabricating a cheap and highly efficient HER electrode on a large-scale for electrochemical water-splitting technology.
- Deng, Chen,Ding, Fei,Li, Xinyuan,Guo, Yaofang,Ni, Wei,Yan, Huan,Sun, Kening,Yan, Yi-Ming
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- Synthesis of transition-metal phosphides from oxidic precursors by reduction in hydrogen plasma
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A series of transition metal phosphides, including MoP, WP, CoP, Co2P, and Ni2P, were synthesized from their oxidic precursors by means of hydrogen plasma reduction under mild conditions. The effects of reduction conditions, such as
- Guan, Jie,Wang, Yao,Qin, Minglei,Yang, Ying,Li, Xiang,Wang, Anjie
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p. 1550 - 1555
(2009/09/30)
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- The synthesis of metal phosphides: Reduction of oxide precursors in a hydrogen plasma
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(Equation Presented) A NiPpy phosphide synthesis: Nickel phosphides such as Ni2P and Ni3P are synthesized stoichiometrically from oxide precursors in a nonthermal hydrogen plasma at atmospheric pressure and low temperature in 60 min (see scheme). This energy- and time-efficient approach can also be applied to the synthesis of other metal phosphides such as GaP, InP, MoP, and WP.
- Wang, Anjie,Qin, Minglei,Guan, Jie,Wang, Li,Guo, Hongchen,Li, Xiang,Wang, Yao,Prins, Roel,Hu, Yongkang
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p. 6052 - 6054
(2009/03/11)
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- The effect of cobalt addition to bulk MoP and Ni2P catalysts for the hydrodesulfurization of 4,6-dimethyldibenzothiophene
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Bulk metal phosphide catalysts with nominal composition CoxNi2P (0 ≤ x ≤ 0.34) and Co0.07MoP were investigated for the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) at 583 K and 3.0 MPa H2. The selectivity for the direct desulfurization (DDS) of 4,6-DMDBT to the product dimethylbiphenyl (DMBP) increased to 49 and 31% over the Co0.08Ni2P and Co0.07MoP catalysts, respectively, compared with the 2P and MoP. Analysis by X-ray photoelectron spectroscopy (XPS) showed that the addition of the Co to MoP and Ni2P resulted in a P enrichment of the catalyst surface. Among the CoxNi2P and Co0.07MoP catalysts studied, the maximum DMBP selectivity occurred for the Co0.08Ni2P catalyst; this catalyst had the highest n-propylamine uptake and lowest CO uptake and the highest P/metal atom ratio, as determined by XPS. The increased selectivity to DMBP suggests that acid sites associated with phosphorous promote skeletal isomerization of 4,6-DMDBT to yield products that readily undergo DDS on the metal sites of the CoxNi2P (0 ≤ x ≤ 0.34) and Co0.07MoP catalysts.
- Abu, Ibrahim I.,Smith, Kevin J.
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p. 356 - 366
(2008/10/09)
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- Preparation of Al, Cr, Nb, Mo, and W monophosphides from a lithium metaphosphate melt
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Synthesis of a series of phosphides (AlP, CrP, NbP, MoP, and WP) by reactions of powdered metals with a melt of lithium metaphosphate LiPO3 was studied. Thermodynamic parameters (ΔH2980, ΔS2980, ΔG2980, and ΔG12730) of the reactions were calculated and their temperature modes were optimized on the basis of the standard thermodynamic characteristics of the initial substances and the reaction products. X-ray patterns of the powders of the obtained compounds are presented.
- Lesnyak,Stratiichuk,Sudavtsova,Slobodyanik
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p. 1274 - 1277
(2007/10/03)
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