A Janus Fe‐SnO2 Catalyst that Enables Bifunctional Electrochemical Nitrogen Fixation

Electrochemical N₂ reduction reactions (NRR) and the N₂ oxidation reaction (NOR), using H₂O and N₂, are a sustainable approach to N₂ fixation. To date, owing to the chemical inertness of nitrogen, emerging electrocatalysts for the electrochemical NRR and NOR at room temperature and atmospheric pressure remain largely underexplored. Herein, a new‐type Fe‐SnO₂ was designed as a Janus electrocatalyst for achieving highly efficient NRR and NOR catalysis. A high NH₃ yield of 82.7 μg h^?1 mg_cat.^?1 and a Faraday efficiency (FE) of 20.4 % were obtained for NRR. This catalyst can also serve as an excellent NOR electrocatalyst with a NO₃^? yields of 42.9 μg h^?1 mg_cat.^?1 and a FE of 0.84 %. By means of experiments and DFT calculations, it is revealed that the oxygen vacancy‐anchored single‐atom Fe can effectively adsorb and activate chemical inert N₂ molecules, lowering the energy barrier for the vital breakage of N≡N and resulting in the enhanced N₂ fixation performance.     

A Spectroscopic Study of Electrochemical Nitrogen and Nitrate Reduction on Rhodium Surfaces

Rh is a promising electrocatalyst for the nitrogen reduction reaction (NRR) given its suitable nitrogen‐adsorption energy and low overpotential. However, the NRR pathway on Rh surfaces remains unknown. In this study, we employ surface‐enhanced infrared‐absorption spectroscopy (SEIRAS) and differential electrochemical mass spectrometry (DEMS) to study the reaction mechanism of NRR on Rh. N₂H_x (0≤x≤2) is detected with a N=N stretching mode at ≈2020 cm^?1 by SEIRAS and a signal at m/z=29 by DEMS. A new two‐step reaction pathway on Rh surfaces is proposed that involves an electrochemical process with a two‐electron transfer to form N₂H₂ and its subsequent decomposition in the electrolyte producing NH₃. Our results also indicate that nitrate reduction and the NRR share the same reaction intermediate N₂H_x.     

Vacancy Engineering of Iron‐Doped W18O49 Nanoreactors for Low‐Barrier Electrochemical Nitrogen Reduction

The electrochemical nitrogen reduction reaction (NRR) is a promising energy‐efficient and low‐emission alternative to the traditional Haber–Bosch process. Usually, the competing hydrogen evolution reaction (HER) and the reaction barrier of ambient electrochemical NRR are significant challenges, making a simultaneous high NH₃ formation rate and high Faradic efficiency (FE) difficult. To give effective NRR electrocatalysis and suppressed HER, the surface atomic structure of W₁₈O₄₉, which has exposed active W sites and weak binding for H₂, is doped with Fe. A high NH₃ formation rate of 24.7 μg h^?1 mg_cat^?1 and a high FE of 20.0 % are achieved at an overpotential of only ?0.15 V versus the reversible hydrogen electrode. Ab initio calculations reveal an intercalation‐type doping of Fe atoms in the tunnels of the W₁₈O₄₉ crystal structure, which increases the oxygen vacancies and exposes more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR.     

Metal‐Ligand Cooperative Synthesis of Benzonitrile by Electrochemical Reduction and Photolytic Splitting of Dinitrogen

Thermal nitrogen fixation relies on strong reductants to overcome the extraordinarily large N?N bond energy. Photochemical strategies that drive N₂ fixation are scarcely developed. Here, the synthesis of a dinuclear N₂‐bridged complex is presented upon reduction of a rhenium(III) pincer platform. Photochemical splitting into terminal nitride complexes is triggered by visible light. Clean nitrogen transfer with benzoyl chloride to free benzamide and benzonitrile is enabled by cooperative 2 H⁺/2 e^? transfer of the pincer ligand. A three‐step cycle is demonstrated for N₂ to nitrile fixation that relies on electrochemical reduction, photochemical N₂‐splitting and thermal nitrogen transfer.     

Surface‐Regulated Rhodium–Antimony Nanorods for Nitrogen Fixation

Surface regulation is an effective strategy to improve the performance of catalysts, but it has been rarely demonstrated for nitrogen reduction reaction (NRR) to date. Now, surface‐rough Rh₂Sb nanorod (RNR) and surface‐smooth Rh₂Sb NR (SNR) were selectively created, and their performance for NRR was investigated. The high‐index‐facet bounded Rh₂Sb RNRs/C exhibit a high NH₃ yield rate of 228.85±12.96 μg h^?1 mg^?1_Rh at ?0.45 V versus reversible hydrogen electrode (RHE), outperforming the Rh₂Sb SNRs/C (63.07±4.45 μg h^?1 mg^?1_Rh) and Rh nanoparticles/C (22.82±1.49 μg h^?1 mg^?1_Rh), owing to the enhanced adsorption and activation of N₂ on high‐index facets. Rh₂Sb RNRs/C also show durable stability with negligible activity decay after 10 h of successive electrolysis. The present work demonstrates that surface regulation plays an important role in promoting NRR activity and provides a new strategy for creating efficient NRR electrocatalysts.     

Defect Engineering Metal‐Free Polymeric Carbon Nitride Electrocatalyst for Effective Nitrogen Fixation under Ambient Conditions

Electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions provides an intriguing picture for the conversion of N₂ into NH₃. However, electrocatalytic NRR mainly relies on metal‐based catalysts, and it remains a grand challenge in enabling effective N₂ activation on metal‐free catalysts. Here we report a defect engineering strategy to realize effective NRR performance (NH₃ yield: 8.09 μg h^?1 mg^?1_cat., Faradaic efficiency: 11.59 %) on metal‐free polymeric carbon nitride (PCN) catalyst. Illustrated by density functional theory calculations, dinitrogen molecule can be chemisorbed on as‐engineered nitrogen vacancies of PCN through constructing a dinuclear end‐on bound structure for spatial electron transfer. Furthermore, the N?N bond length of adsorbed N₂ increases dramatically, which corresponds to “strong activation” system to reduce N₂ into NH₃. This work also highlights the significance of defect engineering for improving electrocatalysts with weak N₂ adsorption and activation ability.     

Ammonia Synthesis Under Ambient Conditions: Selective Electroreduction of Dinitrogen to Ammonia on Black Phosphorus Nanosheets

Constructing efficient catalysts for the N₂ reduction reaction (NRR) is a major challenge for artificial nitrogen fixation under ambient conditions. Herein, inspired by the principle of “like dissolves like”, it is demonstrated that a member of the nitrogen family, well‐exfoliated few‐layer black phosphorus nanosheets (FL‐BP NSs), can be used as an efficient nonmetallic catalyst for electrochemical nitrogen reduction. The catalyst can achieve a high ammonia yield of 31.37 μg h^?1 mg^?1_cat. under ambient conditions. Density functional theory calculations reveal that the active orbital and electrons of zigzag and diff‐zigzag type edges of FL‐BP NSs enable selective electrocatalysis of N₂ to NH₃ via an alternating hydrogenation pathway. This work proves the feasibility of using a nonmetallic simple substance as a nitrogen‐fixing catalyst and thus opening a new avenue towards the development of more efficient metal‐free catalysts.     

ZIF‐Induced d‐Band Modification in a Bimetallic Nanocatalyst: Achieving Over 44 % Efficiency in the Ambient Nitrogen Reduction Reaction

The electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance owing to preferential catalyst–H formation and the consequential hydrogen evolution reaction (HER). Now, the Pt/Au electrocatalyst d‐band structure is electronically modified using zeolitic imidazole framework (ZIF) to achieve a Faradaic efficiency (FE) of >44 % with high ammonia yield rate of >161 μg mg_cat^?1 h^?1 under ambient conditions. The strategy lowers electrocatalyst d‐band position to weaken H adsorption and concurrently creates electron‐deficient sites to kinetically drive NRR by promoting catalyst–N₂ interaction. The ZIF coating on the electrocatalyst doubles as a hydrophobic layer to suppress HER, further improving FE by >44‐fold compared to without ZIF (ca. 1 %). The Pt/Au‐N_ZIF interaction is key to enable strong N₂ adsorption over H atom.     

Greatly Improving Electrochemical N2 Reduction over TiO2 Nanoparticles by Iron Doping

Titanium‐based catalysts are needed to achieve electrocatalytic N₂ reduction to NH₃ with a large NH₃ yield and a high Faradaic efficiency (FE). One of the cheapest and most abundant metals on earth, iron, is an effective dopant for greatly improving the nitrogen reduction reaction (NRR) performance of TiO₂ nanoparticles in ambient N₂‐to‐NH₃ conversion. In 0.5 m LiClO₄, Fe‐doped TiO₂ catalyst attains a high FE of 25.6 % and a large NH₃ yield of 25.47 μg h^?1 mg_cat^?1 at ?0.40 V versus a reversible hydrogen electrode. This performance compares favorably to those of all previously reported titanium‐ and iron‐based NRR electrocatalysts in aqueous media. The catalytic mechanism is further probed with theoretical calculations.     

A Janus Fe-SnO2 Catalyst that Enables Bifunctional Electrochemical Nitrogen Fixation

Electrochemical N₂ reduction reactions (NRR) and the N₂ oxidation reaction (NOR), using H₂O and N₂, are a sustainable approach to N₂ fixation. To date, owing to the chemical inertness of nitrogen, emerging electrocatalysts for the electrochemical NRR and NOR at room temperature and atmospheric pressure remain largely underexplored. Herein, a new-type Fe-SnO₂ was designed as a Janus electrocatalyst for achieving highly efficient NRR and NOR catalysis. A high NH₃ yield of 82.7 μg h⁻¹ mg_cat.⁻¹ and a Faraday efficiency (FE) of 20.4 % were obtained for NRR. This catalyst can also serve as an excellent NOR electrocatalyst with a NO₃⁻ yields of 42.9 μg h⁻¹ mg_cat.⁻¹ and a FE of 0.84 %. By means of experiments and DFT calculations, it is revealed that the oxygen vacancy-anchored single-atom Fe can effectively adsorb and activate chemical inert N₂ molecules, lowering the energy barrier for the vital breakage of N≡N and resulting in the enhanced N₂ fixation performance.     

Pulsed Electrocatalysis Enabling High Overall Nitrogen Fixation Performance for Atomically Dispersed Fe on TiO2

Atomically dispersed Fe was designed on TiO₂ and explored as a Janus electrocatalyst for both nitrogen oxidation reaction (NOR) and nitrogen reduction reaction (NRR) in a two-electrode system. Pulsed electrochemical catalysis (PE) was firstly involved to inhibit the competitive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Excitingly, an unanticipated yield of 7055.81 μmol h⁻¹ g⁻¹_cat. and 12 868.33 μmol h⁻¹ g⁻¹_cat. were obtained for NOR and NRR at 3.5 V, respectively, 44.94 times and 7.8 times increase in FE than the conventional constant voltage electrocatalytic method. Experiments and density functional theory (DFT) calculations revealed that the single-atom Fe could stabilize the oxygen vacancy, lower the energy barrier for the vital rupture of N≡N, and result in enhanced N₂ fixation performance. More importantly, PE could effectively enhance the N₂ supply by reducing competitive O₂ and H₂ agglomeration, inhibit the electrocatalytic by-product formation for longstanding *OOH and *H intermediates, and promote the non-electrocatalytic process of N₂ activation.     

Potassium‐Ion‐Assisted Regeneration of Active Cyano Groups in Carbon Nitride Nanoribbons: Visible‐Light‐Driven Photocatalytic Nitrogen Reduction

As a metal‐free nitrogen reduction reaction (NRR) photocatalyst, g‐C₃N₄ is available from a scalable synthesis at low cost. Importantly, it can be readily functionalized to enhance photocatalytic activities. However, the use of g‐C₃N₄‐based photocatalysts for the NRR has been questioned because of the elusive mechanism and the involvement of N defects. This work reports the synthesis of a g‐C₃N₄ photocatalyst modified with cyano groups and intercalated K⁺ (mCNN), possessing extended visible‐light harvesting capacity and superior photocatalytic NRR activity (NH₃ yield: 3.42 mmol g^?1 h^?1). Experimental and theoretical studies suggest that the ‐C≡N in mCNN can be regenerated through a pathway analogous to Mars van Krevelen process with the aid of the intercalated K⁺. The results confirm that the regeneration of the cyano group not only enhances photocatalytic activity and sustains the catalytic cycle, but also stabilizes the photocatalyst.     

Amorphous core/shell Ti-doped SnO2 with synergistically improved N2 adsorption/activation and electrical conductivity for electrochemical N2 reduction

Electrochemical nitrogen reduction reaction (NRR) has been considered as an appealing and sustainable method to produce ammonia from N₂ under ambient conditions, attracting increasing interest. Limited by low solubility of N₂ in water and high stability of NN triple bond, developing NRR electrocatalysts with both strong N₂ adsorption/activation and high electrical conductivity remain challenging. Here, we demonstrate an efficient strategy to develop NRR electrocatalyst with synergistically enhanced N₂ adsorption/activation and electrical conductivity by heteroatom doping. Combining computational and experimental study, the DFT-designed Ti-doped SnO₂ exhibits significantly enhanced NRR performance with ammonia yield rate of 13.09 µg h^?1 mg^?1 at ?0.2 V vs. RHE. Particularly, the Faradaic efficiency reaches up to 42.6%, outperforming most of Sn-based electrocatalysts. The fundamental mechanism for improving NRR performance of SnO₂ by Ti doping is also revealed. Our work highlights a powerful strategy for developing high-activity electrocatalysts for NRR and beyond.     

Crystal‐Phase‐Engineered PdCu Electrocatalyst for Enhanced Ammonia Synthesis

Crystal phase engineering is a powerful strategy for regulating the performance of electrocatalysts towards many electrocatalytic reactions, while its impact on the nitrogen electroreduction has been largely unexplored. Herein, we demonstrate that structurally ordered body‐centered cubic (BCC) PdCu nanoparticles can be adopted as active, selective, and stable electrocatalysts for ammonia synthesis. Specifically, the BCC PdCu exhibits excellent activity with a high NH₃ yield of 35.7 μg h^?1 mg^?1_cat, Faradaic efficiency of 11.5 %, and high selectivity (no N₂H₄ is detected) at ?0.1 V versus reversible hydrogen electrode, outperforming its counterpart, face‐centered cubic (FCC) PdCu, and most reported nitrogen reduction reaction (NRR) electrocatalysts. It also exhibits durable stability for consecutive electrolysis for five cycles. Density functional theory calculation reveals that strong orbital interactions between Pd and neighboring Cu sites in BCC PdCu obtained by structure engineering induces an evident correlation effect for boosting up the Pd 4d electronic activities for efficient NRR catalysis. Our findings open up a new avenue for designing active and stable electrocatalysts towards NRR.     

Reactive Ionic Liquid Enables the Construction of 3D Rh Particles with Nanowire Subunits for Electrocatalytic Nitrogen Reduction

Until now, the synthesis of Rh particles with unusual three‐dimensional (3D) nanostructures is still challenging. A 3D nanostructure enables fast ion/molecule transport and possesses plenty of exposed active surface, and therefore it is of great interest to construct 3D Rh particles catalysts for the N₂ reduction reaction (NRR). Herein, we proposed a reactive ionic liquid strategy for fabricating unusual 3D Rh particles with nanowires as the subunits. The ionic liquid n‐octylammonium formate simultaneously worked as reaction medium, reductant and template for the successful construction of 3D Rh particles. The as‐prepared 3D Rh particles demonstrated excellent activity for electrocatalytic N₂ fixation in 0.1 M KOH electrolyte under ambient conditions with a high NH₃ yield of 35.58 μg h^?1 mg_cat.^?1 at ?0.2 V versus reversible hydrogen electrode (RHE), surpassing most of the state‐of‐the‐art noble metal catalysts. Our reactive ionic liquid strategy thus holds great promise for the rational construction of high‐performance electrocatalysts toward NRR.     

Tuning the Electron Localization of Gold Enables the Control of Nitrogen‐to‐Ammonia Fixation

The (photo)electrochemical N₂ reduction reaction (NRR) provides a favorable avenue for the production of NH₃ using renewable energy in mild operating conditions. Understanding and building an efficient catalyst with high NH₃ selectivity represents an area of intense interest for the early stages of development for NRR. Herein, we introduce a CoO_x layer to tune the local electronic structure of Au nanoparticles with positive valence sites for boosting conversion of N₂ to NH₃. The catalysts, possessing high average oxidation states (ca. 40 %), achieve a high NH₃ yield rate of 15.1 μg cm^?2 h^?1 and a good faradic efficiency of 19 % at ?0.5 V versus reversible hydrogen electrode. Experimental results and simulations reveal that the ability to tune the oxidation state of Au enables the control of N₂ adsorption and the concomitant energy barrier of NRR. Altering the Au oxidation state provides a unique strategy for control of NRR in the production of valuable NH₃.     

In situ localization of BiVO4 onto two-dimensional MXene promoting photoelectrochemical nitrogen reduction to ammonia

The existing industrial ammonia synthesis usually adopts the Haber-Bosch process, which requires harsh conditions of high temperature and high pressure, and consumes high energy. Under this circumstance, photoelectrochemical (PEC) catalysis is regarded as a promising method for N₂ reduction reaction (NRR), but bears problems of low efficiency and yield. Thus, exploring active catalysts remains highly desirable. In this work, BiVO₄@MXene hybrids have been facilely synthesized by a hydrothermal route. The heterojunctions by the in situ growth of BiVO₄ onto two-dimensional (2D) MXene greatly increase the NRR efficiency: under photoelectric conditions, the optimized NH₃ yield is 27.25 µg h ^{? 1} cm^?2, and the Faraday efficiency achieves 17.54% at ?0.8 V relative to the reversible hydrogen electrode (RHE), which are higher than most state-of-the-art NRR (photo) electrocatalysts. The mechanism speculation shows the enhanced light absorption range and the heterojunction formation largely promote the separation and the transfer efficiency of photogenerated carriers, thereby improving the PEC catalytic ability. Therefore, this work provides a hybrid route to combine the advantages of photo and electric catalysis for effective artificial nitrogen fixation.     

The Unexpected Mechanism Underlying the High‐Valent Mono‐Oxo‐Rhenium(V) Hydride Catalyzed Hydrosilylation of CN Functionalities: Insights from a DFT Study

In this study, we theoretically investigated the mechanism underlying the high‐valent mono‐oxo‐rhenium(V) hydride Re(O)HCl₂(PPh₃)₂ ( 1 ) catalyzed hydrosilylation of C?N functionalities. Our results suggest that an ionic S_N2‐Si outer‐sphere pathway involving the heterolytic cleavage of the Si?H bond competes with the hydride pathway involving the C?N bond inserted into the Re?H bond for the rhenium hydride ( 1 ) catalyzed hydrosilylation of the less steric C?N functionalities (phenylmethanimine, PhCH=NH, and N‐phenylbenzylideneimine, PhCH=NPh). The rate‐determining free‐energy barriers for the ionic outer‐sphere pathway are calculated to be ～28.1 and 27.6 kcal mol^?1, respectively. These values are slightly more favorable than those obtained for the hydride pathway (by ～1–3 kcal mol^?1), whereas for the large steric C?N functionality of N,1,1‐tri(phenyl)methanimine (PhCPh=NPh), the ionic outer‐sphere pathway (33.1 kcal mol^?1) is more favorable than the hydride pathway by as much as 11.5 kcal mol^?1. Along the ionic outer‐sphere pathway, neither the multiply bonded oxo ligand nor the inherent hydride moiety participate in the activation of the Si?H bond.     

Nanoporous Gold Embedded ZIF Composite for Enhanced Electrochemical Nitrogen Fixation

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.     

W/Mo-polyoxometalate-derived electrocatalyst for high-efficiency nitrogen fixation

Ammonia is the feedstock chemical for most fertilizers and the alternative of renewable energy carriers. Environmentally benign electrochemical nitrogen reduction reaction (NRR) under mild conditions has been recognized as one of the most attractive strategies for N₂ fixation. Herein, inspired by Mo-based nitrogenase, W/Mo-doping electrocatalysts were developed with mixed-metal polyoxometalate H₃PW₆Mo₆O₄₀ as the precursor for high performance electrocatalytic NRR. Trace amount of Pt was transplanted on the surface of W/Mo@rGO via in situ electroplating treatment to further improve the NRR performance. The resulting Pt-W/Mo@rGO-6 achieves excellent performance for NRR with a high NH₃ yield of 79.2 µg h^?1 mg_cat^?1 due to the multicomponent synergistic effect in the composite catalyst. The Pt-W/Mo@rGO-6 represents the first example of highly efficient NRR electraocatalyst derived from mixed-metal polyoxometalate, which exhibits outstanding stability confirmed by the constant catalytic performance over 24 h chronoamperometric test. This finding opens a new avenue to construct highly efficient NRR electrocatalyst by employing mixed metal polyoxometalate as the precursor under ambient conditions.