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As a carbon-free reaction process, the electrocatalytic nitrogen reduction reaction (eNRR) under mild conditions has broad prospects for green and sustainable NH3 production. In this work, bimetallic RhRu nanoalloys (NAs) with cross-linked curly nanosheets were successfully prepared and exhibited exciting results in the eNRR process. Furthermore, the composition effect of RhRu NAs on eNRR activity was studied systematically, and the results showed that Rh0.6Ru0.4 NAs/CP exhibited the highest NH3 yield rate of 57.75 μg h-1 mgcat.-1 and faradaic efficiency of 3.39%. As an eNRR catalyst with great potential, Rh0.6Ru0.4 NAs extend the possibility of alloy-nanomaterials in the eNRR field and further provide an idea for the precise structure of more effective and stable electrocatalysts.

Shape-memory materials can retain their functionalities during mechanical deformation, and thus hold great promise for utilizations in versatile, wearable and portable systems. Here, we report a shape-memory V3O7·H2O monolith that works as a new emerging foldable electrocatalyst for nitrogen reduction reaction (NRR). Remarkably, the electrocatalyst has been designed according to our unexpected observation that metal oxides, commonly considered as a class of tough and brittle materials, can show shape-memory properties after anisotropic alignment of their microstructures via an ice-Templated freeze-casting method. We demonstrate the V3O7·H2O electrocatalyst for promoting the NRR characteristic of excellent performances, including an ammonia yield rate of 36.42 μg h-1 mg-1, faradaic efficiency of 14.20% at-0.55 V (vs. RHE), and operation for seven cycles without activity or structural degradation. Remarkably, NRR faradaic efficiencies do not change during electrode deformations, while ammonia yield rates only show a slight decline even after significant foldings. We further elucidate through density function theory that NRR proceeds at vanadium active sites of V3O7·H2O via the associative distal pathway with ?N2 + H+ → ?N2H as the rate-limiting step. This journal is

Surface structure effect is the key subject in electrocatalysis, and consists of the structure dependence of interaction between reaction molecules and the catalyst surface in specifying the surface atomic arrangement, chemical composition and electronic structure. Herein, we develop a controllable synthesis of Pt-RE (RE = La, Y, Sc) alloy concave nanocubes (PtRENCs) with {410} high-index facets (HIFs) by an electrochemical method in a choline chloride-urea based deep eutectic solvent. The PtRENCs are used as an efficient catalyst in electrocatalytic nitrogen reduction to ammonia (NH3). Owing to the high density of low-coordinated Pt step sites (HIF structure) and the unique electronic effect of Pt-RE, the as-prepared PtRENCs exhibit an excellent electrocatalytic performance for the nitrogen reduction reaction (NRR) under ambient conditions. The NH3 yield rate and faradaic efficiency (FE) share the same trend of Pt-La (rNH3: 71.4 μg h-1 μgcat-1, FE: 35.6%) > Pt-Y (rNH3: 65.2 μg h-1 μgcat-1, FE: 26.7%) > Pt-Sc (rNH3: 48.5 μg h-1 μgcat-1, FE: 19%) > Pt (rNH3: 25.8 μg h-1 μgcat-1, FE: 10.7%). Moreover, the PtRENCs demonstrate high selectivity for N2 reduction to NH3 and high stability retaining 90% of the NH3 yield rate and FE values after 12 h continuous NRR tests. Density functional theory (DFT) calculations indicate that the rate determining step of the NRR process is the formation of N2H2? from N2 with the transfer of two proton-coupled electrons, and the upshift of the d-band center boosts the NRR activity by enhancing the bonding strength of reaction intermediates on the high-index faceted Pt-RE (RE = La, Y, Sc) alloying surface. In addition, the introduction of RE (RE = La, Y, Sc) on the Pt step surface can effectively suppress the HER process and provide appropriate sites for the NRR. This journal is

Bismuth has been regarded as a promising electrocatalyst for triggering nitrogen reduction to ammonia, due to the ease of nitrogen dissociation rendered by the strong interaction between Bi 6p band and the N 2p orbitals. However, the poor conductivity of bismuth limits the electron transfer for nitrogen reduction. In addition, the sluggish water dissociation on the bismuth surface leads to insufficient proton supply for the protonation step of *N2, causing inferior ammonia production performance. In this work, we prepare an integrated and binder-free bismuth nanoparticles@nickel foam electrode for ambient ammonia synthesis via a facile displacement reaction. Using nickel foam as the conductive substrate improves the electron transfer of bismuth for nitrogen reduction to ammonia. In addition, enhanced water dissociation on the nickel surface improves the protonation of *N2 by supplying adequate protons via hydrogen spillover, thus boosting the ammonia production performance. This integrated electrode eliminates the use of polymer binders and reduces the contact resistance between the diffusion layer and catalyst layer, facilitating electron delivery and reducing cell resistance, thus requiring less energy input for ammonia production. The performance examination in an electrochemical H-type cell shows that an ammonia yield rate as high as of 9.3 × 10?11 mol s?1 cm?2 and a Faradaic efficiency of 6.3% are achieved. An ammonia yield rate of 8.19 × 10?11 mol s?1 cm?2 is observed after 6 cycles, with a retention rate of 88%.

Based on an ion exchange and dissolution-recrystallization mechanism, rigid indium metal-organic framework (In-MOF) nanosheets have been synthesized under mild conditions. The collective advantages of the rigid structure and two-dimensional architecture (thickness: 1.3 nm) enable In-MOF to show great activity during nitrogen electroreduction and excellent stability over a wide pH range. At pH values ?1mg?1(or 4.94 μg h?1cm?2) and faradic efficiency ≥6.72%. At pH values ≥7, 2D In-MOF can operate efficiently with a record NH3yield of 79.20 μg h?1mg?1(or 15.94 μg h?1cm?2) and faradic efficiency of 14.98%, making it one of the most active MOF-based electrocatalysts for nitrogen electroreduction. Furthermore, the reaction mechanism of nitrogen electroreduction has been revealed using density function theory (DFT) simulations, and it follows enzymatic pathways at all pH values, with the potential determining step being *H2NNH2* → *NH2+ NH3. It is expected that the present study will offer valuable clues for the design and fabrication of low-cost and efficient all-pH nitrogen reduction electrocatalysts for industrial applications.

The electrocatalytic N2reduction reaction (NRR) to ammonia (NH3) driven by intermittent renewable electricity under ambient conditions offers an alternative to the energy-intensive Haber-Bosch process. However, as a distinct core of the process, the design strategy of the electrocatalyst for enhancing the N2activation ability is still in a trial-and-error stage due to the absence of theoretical guidance. As a result, the corresponding NH3yield rate and selectivity are much lower than that required for implementation at scale. In this work, on the basis of the hard-soft acid-base theory, we report a paradigm for the design of an electrocatalyst with tuned Lewis acidity to efficiently activate and reduce N2to NH3. As a proof of concept, it is revealed that enhancing the Lewis acidity of the molybdenum sulfide (MoSx) model catalyst supported on carbon nanotubes can greatly improve its activation ability toward the N2molecule. Accordingly, a high faradaic efficiency of 21.60 ± 2.35% and NH3yield rate of 40.4 ± 3.6 μg h?1mgcat.?1are obtained over the modified MoSx, which are ～2 times enhanced in comparison with the original MoSx, respectively. Density functional theory calculations verify that the electron transfer from the occupied σ orbitals of N2to the empty d orbitals of Mo sites within MoSxcan be greatly accelerated by tuning the Lewis acidity of MoSxto match with the basicity of N2, thereby enhancing the N2activation processviathe σ → d donation mechanism.

This work presents a redox-mediated electrolytic nitrogen reduction reaction (RM-eNRR) using polyoxometalate (POM) as the electron and proton carrier which frees the TiO2-based catalyst from the electrode and shifts the reduction of nitrogen to a reactor tank. The RM-eNRR process has achieved an ammonium production yield of 25.1 μg h?1 or 5.0 μg h?1 cm?2 at an ammonium concentration of 6.7 ppm. With high catalyst loading, 61.0 ppm ammonium was accumulated in the electrolyte upon continuous operation, which is the highest concentration detected for ambient eNRR so far. The mechanism underlying the RM-eNRR was scrutinized both experimentally and computationally to delineate the POM-mediated charge transfer and hydrogenation process of nitrogen molecule on the catalyst. RM-eNRR is expected to provide an implementable solution to overcome the limitations in the conventional eNRR process.

A new type of dititanium dinitrogen complex supported by a triphenolamine (TPA) ligand is reported. Analysis by single-crystal X-ray diffraction and Raman and NMR spectroscopy reveals different coordination geometries for the two titanium centers. Hence, coordination of TPA and a nitrogen ligand results in trigonal-bipyramidal geometry, while an octahedral titanium center is obtained upon additional coordination of an ethoxide generated upon C-O bond cleavage in a diethyl ether solvent molecule. The titanium complex successfully generates ammonia in the presence of an excess amount of PCy3HI and KC8 in 154% yield (per titanium atom). A titanium complex with a bulkier TPA does not form a dinitrogen complex, and mononuclear titanium dinitrogen complexes were not accessible, presumably because of the high tendency of early transition metals to form binuclear dinitrogen complexes.

Hydrazine is a chemical of utmost importance in our society, either for organic synthesis or energy use. The direct conversion of NH3 to hydrazine is highly appealing, but it remains a very difficult task because the degradation of hydrazine is thermodynamically more feasible than the cleavage of the N?H bond of NH3. As a result, any catalyst capable of activating NH3 will thus unavoidably decompose N2H4. Here we show that cavitation bubbles, created by ultrasonic irradiation of aqueous NH3 at a high frequency, act as microreactors to activate and convert NH3 to NH species, without assistance of any catalyst, yielding hydrazine at the bubble–liquid interface. The compartmentation of in-situ-produced hydrazine in the bulk solution, which is maintained close to 30 °C, advantageously prevents its thermal degradation, a recurrent problem faced by previous technologies. This work also points towards a path to scavenge .OH radicals by adjusting the NH3 concentration.

The industrial-scale NH3 production still heavily depends on the Haber-Bosch process, which not only demands high energy consumption but also emits a large amount of CO2. The electrochemical fixation of N2 to NH3 under ambient conditions is regarded as an eco-friendly and sustainable approach, but stable and efficient electrocatalysts are demanded for the N2 reduction reaction under ambient conditions. In this communication, ReS2 nanosheet array on carbon cloth (ReS2/CC) is first utilized in NRR. This ReS2/CC exhibits high catalytic activity and strong long-term electrochemical durability. The Faraday efficiency of ReS2/CC is 0.78% and the NH3 yield of ReS2/CC is 3.61 × 10-10 mol s-1 cm-2 at -0.4 V versus reversible hydrogen electrode in 0.1 M HCl.

The Haber-Bosch process is widely used to convert atmospheric nitrogen (N2) into ammonia (NH3). However, the extreme reaction conditions and abundant carbon released by this process make it important to develop a greener NH3 production method. The electrochemical nitrogen reduction reaction (NRR) is an attractive alternative to the Haber-Bosch process. Herein, we demonstrated that molybdenum sulfide on nickel foil (1T-MoS2-Ni) with low crystallinity was an active NRR electrocatalyst. 1T-MoS2-Ni achieved a high faradaic efficiency of 27.66% for the NRR at -0.3 V (vs. RHE) in a LiClO4 electrolyte. In situ X-ray diffraction and ex situ X-ray photoemission analyses showed that lithium ions were intercalated into the 1T-MoS2 layers during the NRR. Moreover, theoretical calculations revealed the differences between six membered rings formed in the 1T-MoS2 and 2H-MoS2 systems with Li intercalation. The bond distances of d(Mo-N) and d(N-Li) of in Li-1T-MoS2 were found to be shorter than those in Li-2H-MoS2, resulting in a lower energy barrier of N2 fixation and higher NRR activity. Therefore, 1T-MoS2-Ni is promising as a scalable and low-cost NRR electrocatalyst with lower power consumption and carbon emission than the Haber-Bosch process.

Carbon-based nanomaterials are widely used in electro-catalysis because of their low cost, high conductivity and stability. However, their application towards selective electrochemical reduction of nitrogen to ammonia suffers from low activity and faradaic efficiency (FE). Here, we report a confined electrocatalysis strategy for enhanced ammonia production and FE in the electrochemical nitrogen reduction reaction (eNRR), by the construction of a carbon nanotube (CNT or NCNT) inserted porous metal-organic framework (MOF). The CNT/NCNT serves as the catalytic center and ensures an efficient pathway for electron conduction that is essential to electrocatalysis, while the general relative hydrophobicity within the MOF enriches the local concentration of N2 near the catalyst active sites, and more importantly suppresses the hydrogen evolution reaction (HER) to facilitate the FE. Among the systematically screened MOF and carbon nanotubes, NCNT@MIL-101(Fe) demonstrates the highest activity of 607.35 μg h-1 mgNCNT-1 and CNT@MIL-101(Fe) achieves the best FE of 37.28%. The significantly improved NRR performance of CNT@MOFs and NCNT@MOFs demonstrates the successful employment of confined catalysis in electrochemical reactions, which provides an alternative strategy for catalyst design in nitrogen fixation. This journal is

In the process of electrochemical ammonia synthesis using an aqueous solution as the electrolyte, most protons will preferentially compete for electrons for hydrogen generation. Herein, the carbon cloth loaded with Nano-Fe was used as the cathode, and a K3PO4 solution was used as the electrolyte. The electrochemical reduction of N2 to NH3 was investigated. It was found that the K3PO4 electrolyte had an obvious promotion effect on the ammonia synthesis efficiency compared with other electrolytes. It was confirmed that phosphorus and potassium had a synergistic effect on the ammonia synthesis efficiency. K+ can effectively prevent H+ from adsorbing to the active site of a catalyst surface, thus inhibiting the formation of hydrogen. The solubility of the phosphate solution for N2 is better than that of other aqueous electrolyte solutions, thus effectively improving the ammonia production efficiency. The highest ammonia yield was 79.0±5×10?11 mol ? s?1 ? cm?2, and the faraday efficiency reached 16.68 %. These results provide an effective way to improve the conversion yield of electrochemical ammonia synthesis in water systems.

Electrolytic ammonia synthesis from nitrogen at ambient conditions is appearing as a promising alternative to the Haber-Bosch process which is consuming high energy and emitting CO2. Here, a typical MOF material, HKUST-1 (Cu?BTC, BTC=benzene-1,3,5-tricarboxylate), was selected as an electrocatalyst for the reaction of converting N2 to NH3 under ambient conditions. At ?0.75 V vs. reversible hydrogen electrode, it achieves excellent catalytic performance in the electrochemical synthesis of ammonia with high NH3 yield (46.63 μg h?1 mg?1 cat. or 4.66 μg h?1 cm?2) and good Faraday efficiency (2.45%). It is indicated that the good performance of the HKUST-1 catalyst may originate from the formation of Cu(I). In addition, the catalyst also has good selectivity for N2 to NH3.

The electrocatalytic nitrogen (N2) reduction reaction is recognized as a green and sustainable approach for ammonia (NH3) synthesis alternative to the traditional industrial method-the Haber-Bosch process, while an efficient electrocatalysis of such a process is a prerequisite for N2 reduction. Developing a cost-effective electrocatalyst for the electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions with an excellent catalytic performance remains a great challenge. Here, we report a facile hydrothermal reaction to synthesize Fe-doped manganese oxide (MnO2) with a nanoneedle morphology as a cost-effective electrocatalyst for the NRR. It is verified that Fe plays a critical role in the NRR. This catalyst shows an excellent catalytic performance with a high faradaic efficiency of 16.8% and a high NH3 formation rate of 39.2 μg h-1 mgcat.-1 at -0.29 V vs. the reversible hydrogen electrode in 0.1 M Na2SO4, which are much higher than those of all reported Mn-based NRR catalysts and many other previously reported catalysts. This catalyst also shows excellent durability during electrolysis and recycling tests. In addition, the electrocatalyst mechanism is also assessed in combination with density functional theory.

NH3, as one of the most massively used chemical products in the world, not only serves as the main nitrogen source of chemical fertilizers but also is considered as a promising renewable energy source. Most ammonia in industry is produced by the Haber-Bosch process under extremely high temperature and pressure conditions, which is intensively energy consuming and environmentally unfriendly. Electrocatalytic nitrogen reduction reaction (NRR) has been regarded as a promising way to produce NH3 under ambient conditions in recent years, but the research for efficient earth-abundant electrocatalysts is still highly limited. In this work, different TiO2 phases (anatase and rutile)/carbon nanocomposites with a sandwich architecture are produced by annealing MXene at different temperatures, which shows excellent electrocatalytic NRR performance. In 0.1 M Na2SO4, anatase TiO2/C composites show better NRR performance than the rutile ones, which achieve a large NH3 yield of 14.0 μg h-1 cm-2, a high Faradaic efficiency of 13.3% at-0.2 V vs a reversible hydrogen electrode, and a high electrochemical stability. The sandwich architecture of anatase TiO2 nanoparticles well-dispersed on the surface of carbon layers could increase the conductivity of TiO2 and the exposure of active sites, which could explain the improved NRR activity of anatase TiO2/C composites compared with previous work. Density functional theory calculations suggest that the energy barrier of most steps for the surface of anatase TiO2 is relatively lower than that of rutile TiO2, which could explain the better electrocatalytic NRR performance for anatase TiO2/C composites compared with the rutile ones.

Achieving an efficient electrochemical nitrogen reduction reaction (ENRR) remains a great challenge, demanding the development of a new strategy for ENRR catalyst engineering. Herein, we demonstrate a largely improved ENRR by the controlled engineering of Ru nanowires with atomic Pt decoration. Specifically, the readily synthesized Ru88Pt12 nanowires exhibit a high NH3 production rate of 47.1 μg h-1 mgcat-1 and faradaic efficiency of 8.9% at -0.2 V, which are 5.3 and 14.6 times higher than those values for Ru nanowires. They also show outstanding stability, as evidenced by the full preservation of the NH3 yield and faradaic efficiency even after 15 h of electrocatalysis. As revealed by theoretical investigations, the d-band center of Ru atoms is upshifted by the tensile strain due to the presence of Pt atoms, leading to the selective enhancement of N2 adsorption and the stabilization of N2H?. Such an atomic engineering method may be applied to precisely tailor other metal nanocatalysts for different applications.

Activation and reduction of N2 have been a major challenge to chemists and the focus since now has mostly been on the synthesis of NH3. Alternatively, reduction of N2 to hydrazine is desirable because hydrazine is an excellent energy vector that can release the stored energy very conveniently without the need for catalysts. To date, only one molecular catalyst has been reported to be able to reduce N2 to hydrazine chemically. A trinuclear T-shaped nickel thiolate molecular complex has been designed to activate dinitrogen. The electrochemically generated all Ni(I) state of this molecule can reduce N2 in the presence of PhOH as a proton donor. Hydrazine is detected as the only nitrogen-containing product of the reaction, along with gaseous H2. The complex reported here is selective for the 4e-/4H+ reduction of nitrogen to hydrazine with a minor overpotential of ～300 mV.

Nitrogen (N2) fixation to produce bio-available ammonia (NH3) is essential to all life but is a challenging transformation to catalyze owing to the chemical inertness of N2. Transition metals can, however, bind N2 and activate it for functionalization. Significant opportunities remain in developing robust and efficient transition metal catalysts for the N2 reduction reaction (N2RR). One opportunity to target in catalyst design concerns the stabilization of transition metal diazenido species (M-NNH) that result from the first N2 functionalization step. Well-characterized M-NNH species remain very rare, likely a consequence of their low N–H bond dissociation free energies (BDFEs). In this essay, we discuss the relationship between the BDFEN–H of a given M-NNH species to the observed overpotential and selectivity for N2RR catalysis with that catalyst system. We note that developing strategies to either increase the N–H BDFEs of M-NNH species, or to avoid M-NNH intermediates altogether, are potential routes to improved N2RR efficiency.

Single-atom catalysts have demonstrated their superiority over other types of catalysts for various reactions. However, the reported nitrogen reduction reaction single-atom electrocatalysts for the nitrogen reduction reaction exclusively utilize metal–nitrogen or metal–carbon coordination configurations as catalytic active sites. Here, we report a Fe single-atom electrocatalyst supported on low-cost, nitrogen-free lignocellulose-derived carbon. The extended X-ray absorption fine structure spectra confirm that Fe atoms are anchored to the support via the Fe-(O-C2)4 coordination configuration. Density functional theory calculations identify Fe-(O-C2)4 as the active site for the nitrogen reduction reaction. An electrode consisting of the electrocatalyst loaded on carbon cloth can afford a NH3 yield rate and faradaic efficiency of 32.1 μg h?1 mgcat.?1 (5350 μg h?1 mgFe?1) and 29.3 percent, respectively. An exceptional NH3 yield rate of 307.7 μg h?1 mgcat.?1 (51 283 μg h?1 mgFe?1) with a near record faradaic efficiency of 51.0 percent can be achieved with the electrocatalyst immobilized on a glassy carbon electrode.

The electrochemical conversion of N2 at ambient conditions using renewably generated electricity is an attractive approach for sustainable ammonia (NH3) production. Considering the chemical inertness of N2, rational design of efficient and stable catalysts is required. Therefore, in this work, it is demonstrated that a C-doped TiO2/C (C-TixOy/C) material derived from the metal–organic framework (MOF) MIL-125(Ti) can achieve a high Faradaic efficiency (FE) of 17.8 %, which even surpasses most of the established noble metal-based catalysts. On the basis of the experimental results and theoretical calculations, the remarkable properties of the catalysts can be attributed to the doping of carbon atoms into oxygen vacancies (OVs) and the formation of Ti?C bonds in C-TixOy. This binding motive is found to be energetically more favorable for N2 activation compared to the non-substituted OVs in TiO2. This work elucidates that electrochemical N2 reduction reaction (NRR) performance can be largely improved by creating catalytically active centers through rational substitution of anions into metal oxides.

Most conventional photoelectrochemical-based methods for synthesizing NH3 show low selectivity due to the generation of H2 as a by-product. In principle, two types of reaction mechanisms can occur in the reduction of N2 to NH3. One is an associative pathway in which N2 molecules on the catalyst are hydrogenated. The other is a dissociative pathway in which nitrogen and hydrogen react after the cleavage of the strong N2 triple bond. Understanding the mechanism of NH3 formation on the electrode will facilitate the development of selective and efficient NH3 synthesis techniques. In this study, we constructed a two-electrode system composed of a strontium titanate photocatalytic anode in which the plasmon effect is expressed by plasmonic gold nanoparticles and a zirconium cathode, which was connected to the external circuit to investigate the reaction by electrochemical analysis in addition to analysis of the product. The bias and pH dependences of the reaction were then systematically investigated, and the plasmon-induced synthesis of NH3 on Zr was proposed to proceed via an associative pathway.

The electrochemical N2 reduction reaction (NRR) in an aqueous medium has recently aroused great attention for the synthesis of NH3 under ambient conditions. However, this process generally suffers from a low NH3 production rate and often requires a noble-metal based electrocatalyst with some sophisticated nanosynthesis method. This work reports a new non-precious, self-supportive iron sulfide (FeSx) NRR electrocatalyst, synthesized by a simple H2S-plasma treatment on low-cost Fe foam. The H2S-plasma treatment sulfurizes the Fe surface to afford a self-supportive FeSx thin layer on the Fe foam (FeSx/Fe). The synthesized FeSx/Fe foam can be directly used as the electrode for the NRR, and it is demonstrated to show a remarkable NH3 production rate of 4.13 × 10-10 mol s-1 cm-2 and a high faradaic efficiency of 17.6%, significantly outperforming many other reported non-precious electrocatalysts. Further material characterization shows that the surface FeSx converts to the mackinawite FeS after the NRR; the mackinawite FeS is possibly the actual high-activity NRR electrocatalyst, and density functional theory calculation is further employed to elucidate the NRR mechanism. Given the high performance and low cost, we envision that the plasma-synthesized FeSx/Fe will be of great promise for the electrochemical NH3 synthesis under ambient conditions.

The electrochemical nitrogen reduction reaction (NRR) offers an energy-saving and environmentally friendly approach to produce ammonia under ambient conditions. However, traditional catalysts have extremely poor NRR performances because of their low activity and the competitive hydrogen evolution reaction. The high catalytic activity of nanoporous gold (NPG) and the hydrophobicity and molecular concentrating effect of the zeolitic imidazolate framework-8 (ZIF-8) were incorporated in the NPG?ZIF-8 nanocomposite so that the ZIF-8 shell could weaken hydrogen evolution and retard reactant diffusion. A highest Faradaic efficiency of 44 % and an excellent rate of ammonia production of (28.7±0.9) μg h?1 cm?2 were achieved, which are superior to traditional gold nanoparticles and NPG. Moreover, the composite catalyst shows high electrochemical stability and selectivity (98 %). The superior NRR performance makes NPG?ZIF-8 one of the most promising water-based NRR electrocatalysts for ammonia production.

Developing noble-metal-free electrocatalysts is important to industrially viable ammonia synthesis through the nitrogen reduction reaction (NRR). However, the present transition-metal electrocatalysts still suffer from low activity and Faradaic efficiency due to poor interfacial reaction kinetics. Herein, an interface-engineered heterojunction, composed of CoS nanosheets anchored on a TiO2 nanofibrous membrane, is developed. The TiO2 nanofibrous membrane can uniformly confine the CoS nanosheets against agglomeration, and contribute substantially to the NRR performance. The intimate coupling between CoS and TiO2 enables easy charge transfer, resulting in fast reaction kinetics at the heterointerface. The conductivity and structural integrity of the heterojunction are further enhanced by carbon nanoplating. The resulting C?CoS?TiO2 electrocatalyst achieves a high ammonia yield (8.09×10?10 mol s?1 cm?2) and Faradaic efficiency (28.6 %), as well as long-term durability.

Using electrocatalytic N2 reduction to make NH3 is considered to be an attractive environmentally-friendly alternative to the Haber-Bosch process, which is rather energy-intensive and has heavy CO2 emissions. However, only limited success has been achieved in identifying metal oxides as effective electrocatalysts for the N2 reduction reaction (NRR) under alkaline conditions. In this communication, we report that a K2Ti4O9 nanobelt is able to effectively electrocatalyze the ambient NRR for N2-to-NH3 fixation at alkaline pH. When tested in 0.1 M KOH, a high NH3 yield of 22.88 μg h-1 mg-1cat. and a faradaic efficiency of 5.87% were attained. Moreover, K2Ti4O9 also demonstrates good selectivity and high electrochemical stability for NH3 formation.

[Problem] high temperature and high pressure condition such as a Bosch process without requiring a high energy · harbor, ammonia nitrogen (nitrogen-fixing method) and low energy method simply as a precursor of ammonia nitrogen - novel chromium complex. (1) A compound represented by the general formula [a], as well as the fixing method using a nitrogen compound. (Where R is an alkyl group, a cycloalkyl group, or an aryl group; R1 Is H or an alkyl group)[Drawing] no (by machine translation)

The production of ammonia (NH3) in the industrial scale basically relies on the traditional technology of Haber-Bosch, which is operated under harsh conditions with high energy consumption and a huge number of greenhouse gas emissions. Electrochemical N2 reduction reaction (NRR) is a promising route for artificial N2-to-NH3 fixation with less energy consumption. However, an effective electrocatalyst, as a prerequisite of the NRR, is of significance. Here, we report that a spinel LiMn2O4 nanofiber acts as a noble-metal-free electrocatalyst for NH3 synthesis with excellent performance under ambient conditions. The electrocatalyst, which was tested in 0.1 M HCl, has an excellent Faradaic efficiency of 7.44% and a NH3 yield of 15.83 μg h-1 mgcat.-1 at -0.50 V versus reversible hydrogen electrode. Moreover, it also possesses excellent electrochemical and structure stability.

The traditional NH3 production method (Haber-Bosch process) is currently complemented by electrochemical synthesis at ambient conditions, but the rather low selectivity (as indicated by the Faradaic efficiency) for the electrochemical reduction of molecular N2 into NH3 impedes the progress. Here, we present a powerful method to significantly boost the Faradaic efficiency of Au electrocatalysts to 67.8% for the nitrogen reduction reaction (NRR) by increasing their electron density through the construction of inorganic donor-acceptor couples of Ni and Au nanoparticles. The unique role of the electron-rich Au centers in facilitating the fixation and activation of N2 was also investigated via theoretical simulation methods and then confirmed by experimental results. The highly coupled Au and Ni nanoparticles supported on nitrogen-doped carbon are stable for reuse and long-term performance of the NRR, making the electrochemical process more sustainable for practical application.

The synthesis of NH3 heavily depends on the energy-intensive Haber-Bosch process with a large amount of greenhouse gas emission. Electrochemical reduction offers a carbon-neutral process to convert N2 to NH3 at ambient conditions, but requires efficient and stable catalysts for the N2 reduction reaction. Mo-dependent nitrogenases and synthetic molecular complexes have attracted increasing attention for N2 fixation; however, less attention has been paid to Mo-based nanocatalysts for electrochemical N2 conversion to NH3. Herein, we report that MoO3 nanosheets act as an efficient non-noble-metal catalyst for electrochemical N2 fixation to NH3 with excellent selectivity at room temperature and atmospheric pressure. In 0.1 M HCl, this catalyst exhibits remarkable NRR activity with an NH3 yield of 4.80 × 10-10 mol s-1 cm-2 (29.43 μg h-1 mgcat.-1) and a faradaic efficiency of 1.9%. Moreover, this catalyst also shows high electrochemical stability and durability. Density functional theory calculations reveal that the outermost Mo atoms serve as the active sites for effective N2 adsorption.

Theory predicts a very rich high pressure chemistry of hydronitrogens with the existence of many NxHy compounds. The stability of these phases under pressure is being investigated by the compression of N2-H2 mixtures of various compositions. A previous study had disclosed a eutectic-type N2-H2 phase diagram with two stoichiometric van der Waals compounds: (N2)6(H2)7 and N2(H2)2. The structure and pressure induced chemistry of the (N2)6(H2)7 compound have already been investigated. Here, we determine the structure of the N2(H2)2 compound and characterize using Raman spectroscopy measurements the chemical changes under a pressure cycle up to 60 GPa and back to ambient conditions. A N2(H2)2 single crystal was grown from a 1:2 N2-H2 mixture and its crystalline structure was solved using synchrotron X-ray diffraction. Similar to the (N2)6(H2)7 solid, N2(H2)2 has a remarkable host-guest structure containing N2 molecules orientationally disordered with spherical, ellipsoidal and planar shapes. Above 50 GPa, N2(H2)2 was found to undergo a chemical reaction. The reaction products were determined to be of the azane family, with NH3 as the main constituent, along with molecular nitrogen. Upon pressure decrease, the reaction products are found to react in such a way that below 10 GPa, hydrazine is the sole azane detected. Observed down to the opening of the diamond anvil cell, the formation of metastable hydrazine instead of the energetically favorable ammonia is puzzling and remains to be elucidated. That could change the current view of Jovian planets' atmospheres in which ammonia is assumed the only stable hydronitrogen molecule.

Newly designed and prepared vanadium complexes bearing anionic pyrrole-based PNP-type pincer and aryloxy ligands were found to work as effective catalysts for the direct conversion of molecular dinitrogen into ammonia and hydrazine under mild reaction con

Dinitrogen-bridged dititanium and dizirconium complexes bearing anionic pyrrole-based PNP-type pincer ligands are prepared and characterized by X-ray analysis. Their catalytic activity is investigated toward reduction of nitrogen gas into ammonia and hydr

Iron-chloride, -dinitrogen, and -methyl complexes bearing anionic carbazole-based PNP-type pincer ligands are designed, prepared and characterized by X-ray analysis. Some iron complexes are found to work as catalysts toward nitrogen fixation under mild re

Late-transition-metal-based catalysts are widely used in N2 fixation reactions, but the reactivity of late-transition-metal N2 complexes, besides iron N2 complexes, has remained poorly understood as their N2 complexes were thought to be labile and hard to functionalize. By employing a monodentate N-heterocyclic carbene (NHC), 1,3-dicyclohexylimidazol-2-ylidene (ICy) as ligand, the cobalt(0)- and cobalt(-1)-N2 complexes, [(ICy)3Co(N2)] (1) and [(ICy)2Co(N2)2M]n (M = K, 2a; Rb, 2b; Cs, 2c), respectively, were synthesized from the stepwise reduction of (ICy)3CoCl by the corresponding alkaline metals under a N2 atmosphere. Complexes 2a-c in their solid states adopt polymeric structures. The N-N distances (1.145(6)-1.162(5) ?) and small N-N infrared stretchings (ca. 1800 and 1900 cm-1) suggest the strong N2 activation of the end-on N2 ligands in 2a-c. One electron oxidation of 1 by [Cp2Fe][BF4] gave the cobalt(I) complex devoid of N2 ligand [(ICy)3Co][BF4] (3). The bis(dinitrogen)cobalt(-1) complexes 2a-c undergo protonation reaction with triflic acid to give N2H4 in 24-30% yields (relative to cobalt). Complexes 2a-c could also react with silyl halides to afford diazene complexes [(ICy)2Co(η2-R3SiNNSiR3)] (R = Me, 6a; Et, 6b) that are the first diazene complexes of late transition metals prepared from N2 functionalization. Characterization data, in combination with calculation results, suggest the electronic structures of the diazene complexes as low-spin cobalt(II) complexes containing dianionic ligand [η2-R3SiNNSiR3]2-. Complexes 1, 2a-c, 6a, 6b, and (ICy)2CoCl2 proved to be effective catalysts for the reductive silylation of N2 to afford N(SiMe3)3. These NHC-cobalt catalysts display comparable turnover numbers (ca. 120) that exceed the reported 3d metal catalysts. The fine performance of the NHC-cobalt complexes in the stoichiometric and catalytic N2-functionalization reactions points out the utility of low-valent low-coordinate group 9 metal species for N2 fixation.

Distinguishing the reactivity differences between N2 complexes having different binding modes is crucial for the design of effective N2-functionalizing reactions. Here, we compare the reactions of a K-bridged, dinuclear FeNNFe complex with a monomeric Fe(N2) complex where the bimetallic core is broken up by the addition of chelating agents. The new anionic iron(0) dinitrogen complex has enhanced electron density at the distal N atoms of coordinated N2, and though the N2 is not as weakened in this monomeric compound, it is much more reactive toward silylation by (CH3)3SiI (TMSI). Double silylation of N2 gives a three-coordinate iron(III) hydrazido(2-) complex, which is finely balanced between coexisting S = 1/2 and S = 3/2 states that are characterized by crystallography, spectroscopy, and computations. These results give insight into the interdependence between binding modes, alkali dependence, reactivity, and magnetic properties within an iron system that functionalizes N2.

NH3 synthesis heavily depends on the energy-intensive Haber-Bosch process, which produces serious carbon emission. Electrocatalytic N2 reduction emerges as an environmentally benign process for sustainable artificial N2 fixation but requires efficient, stable and selective catalysts for the N2 reduction reaction (NRR). Here, we report that Cr2O3 nanofiber behaves as a superb non-noble-metal NRR electrocatalyst for artificial N2 fixation to NH3, with excellent selectivity under ambient conditions. In 0.1 M HCl, this catalyst achieves a high Faradaic efficiency of 8.56% and a high NH3 formation rate of 28.13 μg h?1 mgcat.?1, placing it amongst the most active aqueous-based NRR electrocatalysts. Moreover, this catalyst also shows strong electrochemical durability during electrolysis and the recycling test. It opens a new avenue to explore the rational design of Cr-based nanostructures as advanced catalysts for N2 fixation and other applications.

The Fe(0) species Fe(N2)(dmpe)2 exists in equilibrium with the previously unreported dimer, [Fe(dmpe2)2(μ-N2)]. For the first time these complexes, alongside Fe(N2)(depe)2, are shown unambiguously to produce N2H4 and/or NH3 upon addition of triflic acid; for Fe(N2)(depe)2 this represents one of the highest electron conversion efficiencies for Fe complexes to date.

Biological N2 fixation to NH3 may proceed at one or more Fe sites in the active-site cofactors of nitrogenases. Modeling individual e-/H+ transfer steps of iron-ligated N2 in well-defined synthetic systems is hence of much interest but remains a significant challenge. While iron complexes have been recently discovered that catalyze the formation of NH3 from N2, mechanistic details remain uncertain. Herein, we report the synthesis and isolation of a diamagnetic, 5-coordinate Fe=NNH2+ species supported by a tris(phosphino)silyl ligand via the direct protonation of a terminally bound Fe-N2- complex. The Fe=NNH2+ complex is redox-active, and low-temperature spectroscopic data and DFT calculations evidence an accumulation of significant radical character on the hydrazido ligand upon one-electron reduction to S = 1/2 Fe=NNH2. At warmer temperatures, Fe=NNH2 rapidly converts to an iron hydrazine complex, Fe-NH2NH2+, via the additional transfer of proton and electron equivalents in solution. Fe-NH2NH2+ can liberate NH3, and the sequence of reactions described here hence demonstrates that an iron site can shuttle from a distal intermediate (Fe=NNH2+) to an alternating intermediate (Fe-NH2NH2+) en route to NH3 liberation from N2. It is interesting to consider the possibility that similar hybrid distal/alternating crossover mechanisms for N2 reduction may be operative in biological N2 fixation.

The first complete structurally and spectroscopically characterized series of isostructural Group 6 N2 complexes is reported. Protonolysis experiments on cis-[M(N2)2(PEtNRPEt)2] (M = Cr, Mo, W; R = 2,6-difluorobenzyl) reveal that only Cr affords N2H5+ and NH4+ from the reduction of the N2 ligands.

A series of azaferrocene-based PNP-type pincer ligands were designed and prepared as new PNP-type pincer ligands. Some transition-metal complexes, including molybdenum, chromium, and iron complexes, bearing these azaferrocene-based PNP-type pincer ligands were also prepared and characterized by X-ray analysis. The stoichiometric and catalytic reactivities of molybdenum–dinitrogen complexes toward nitrogen fixation were investigated in detail.

Even though the well-established Haber-Bosch process has been the major artificial way to 'fertilize' the earth, its energy-intensive nature has been motivating people to learn from nitrogenase, which can fix atmospheric N2 to NH3 in vivo under mild conditions with its precisely arranged proteins. Here we demonstrate that efficient fixation of N2 to NH3 can proceed under room temperature and atmospheric pressure in water using visible light illuminated BiOBr nanosheets of oxygen vacancies in the absence of any organic scavengers and precious-metal cocatalysts. The designed catalytic oxygen vacancies of BiOBr nanosheets on the exposed {001} facets, with the availability of localized electrons for-back-donation, have the ability to activate the adsorbed N2, which can thus be efficiently reduced to NH3 by the interfacial electrons transferred from the excited BiOBr nanosheets. This study might open up a new vista to fix atmospheric N2 to NH3 through the less energy-demanding photochemical process.

Novel molybdenum-dinitrogen complexes bearing a PNN-type pincer ligand are designed, prepared, and characterized spectroscopically. Molecular structures of molybdenum trichloride and molybdenum-dinitrogen complexes bearing trimethylphosphine are confirmed by X-ray analysis. Stoichiometric and catalytic reactions are investigated, where only a stoichiometric amount of ammonia is produced based on the molybdenum atom of the complexes. These results indicate that reactive behaviors of molybdenum-dinitrogen complexes are depending on the nature of the pincer ligands.

The deprotection of wide varieties of oximes, imines, and azines to their corresponding carbonyls has been achieved using Cu-nanoparticles on a cellulose template as a reusable catalyst. The reactions were carried out at 80-100 °C using microwave irradiation in water under neutral condition. The catalyst can be reused for several cycles with good to excellent yield.

Hydroxylamine reacts as an oxygen nucleophile, most likely via its ammonia oxide tautomer, towards both phosphate di- and triesters of 2-hydroxypyridine. But the reactions are very different. The product of the two-step reaction with the triester TPP is trapped by the NH2OH present in solution to generate diimide, identified from its expected disproportionation and trapping products. The reaction with H3N+-O- shows general base catalysis, which calculations show is involved in the breakdown of the phosphorane addition-intermediate of a two-step reaction. The reactivity of the diester anion DPP- is controlled by its more basic pyridyl N. Hydroxylamine reacts preferentially with the substrate zwitterion DPP ± to displace first one then a second 2-pyridone, in concerted SN2(P) reactions, forming O-phosphorylated products which are readily hydrolysed to inorganic phosphate. The suggested mechanisms are tested and supported by extensive theoretical calculations.

A dinitrogen-bridged dimolybdenum-tetrachloride complex is prepared and reduced with Super-Hydride (LiBHEt3) to afford the corresponding dimolybdenum-dinitrogen complex together with the formation of molecular dihydrogen. This reaction proceeds via the ligand exchange of the coordinated dihydrogen generated in situ with molecular dinitrogen.

The environmentally friendly reduction and a solution processability of chemically modified graphene nanosheets are most important for their applications. Here we report for the first time that in situ synthesis of hydrazine and spontaneous reduction of g

The recombination rate constant for the NH2(X2B 1) + NH2(X2B1) → N 2H4(X1A1) reaction in He, Ne, Ar, and N2 was measured over the pressure range 1-20 Torr at a temperature of 296 K. The NH2 radical was produced by 193 nm laser photolysis of NH3 dilute in the third-body gas. The production of NH2 and the loss of NH3 were monitored by high-resolution continuous-wave absorption spectroscopy: NH2 on the 1221 ← 1331 rotational transition of the (0,7,0)A2A1 ← (0,0,0) X 2B1 vibronic band and NH3 on either inversion doublet of the qQ3(3) rotational transition of the ν1 fundamental. Both species were detected simultaneously following the photolysis laser pulse. The broader Doppler width of the NH 2 spectral transition allowed temporal concentration measurements to be extended up to 20 Torr before pressure broadening effects became significant. Fall-off behavior was identified and the bimolecular rate constants for each collision partner were fit to a simple Troe form defined by the parameters, k0, kinf, and Fcent. This work is the first part of a two part series in which part 2 will discuss the measurements with more efficient energy transfer collision partners CH4, C 2H6, CO2, CF4, and SF6. The pressure range was too limited to extract any new information on k inf, and kinf was taken from the theoretical calculations of Klippenstein et al. (J. Phys. Chem A 2009, 113, 10241) as kinf = 7.9 × 10-11 cm3 molecule-1 s-1 at 296 K. The individual Troe parameters were: He, k0 = 2.8 × 10-29 and Fcent = 0.47; Ne, k0 = 2.7 × 10-29 and Fcent = 0.34; Ar, k0 = 4.4 × 10-29 and Fcent = 0.41; N2, k0 = 5.7 × 10-29 and Fcent = 0.61, with units cm6 molecule-2 s-1 for k0. In the case of N 2 as the third body, it was possible to measure the recombination rate constant for the NH2 + H reaction near 20 Torr total pressure. The pure three-body recombination rate constant was (2.3 ± 0.55) × 10-30 cm6 molecule-2 s-1, where the uncertainty is the total experimental uncertainty including systematic errors at the 2σ level of confidence.

Novel molybdenum- and tungsten-dinitrogen complexes bearing PNP-type pincer ligands are prepared and characterized by X-ray analysis. Reactions of these molybdenum- and tungsten-dinitrogen complexes with an excess amount of sulfuric acid in THF at room temperature afford ammonia and hydrazine in good yields.

Substituted bicyclic carboxamide and urea compounds corresponding to formula (I) processes for the preparation thereof, pharmaceutical compositions containing these compounds, and a method of using these compounds for the treatment and/or inhibition of pain and other conditions mediated at least in part via the vanilloid receptor 1.