Bismuth-Based Electrocatalysts for Identical Value-Added Formic Acid Through Coupling CO2 Reduction and Methanol Oxidation.

It is an effective way to reduce atmospheric CO2 via electrochemical CO2 reduction reaction (CO2 RR), while the slow oxygen evolution reaction (OER) occurs at the anode with huge energy consumption. Herein, methanol oxidation reaction (MOR) is used to replace OER, coupling CO2 RR to achieve co-production of formate. Through enhancing OCHO* adsorption by oxygen vacancies engineering and synergistic effect by heteroatom doping, Bi/Bi2 O3 and Ni─Bi(OH)3 are synthesized for efficient production of formate via simultaneous CO2 RR and methanol oxidation reaction (MOR), achieving that the coupling of CO2 RR//MOR only required 7.26 kWh gformate -1 power input, much lower than that of CO2 RR//OER (13.67 kWh gformate -1 ). Bi/Bi2 O3 exhibits excellent electrocatalytic CO2 RR performance, achieving FEformate >80% in a wide potential range from -0.7 to -1.2 V (vs RHE). For MOR, Ni─Bi(OH)3 exhibits efficient MOR catalytic performance with the FEformate >98% in the potential range of 1.35-1.6 V (vs RHE). Not only demonstrates the two-electrode systems exceptional stability, working continuously for over 250 h under a cell voltage of 3.0 V, but the cathode and anode can maintain a FE of over 80%. DFT calculation results reveal that the oxygen vacancies of Bi/Bi2 O3 enhance the adsorption of OCHO* intermediate, and Ni─Bi(OH)3 reduce the energy barrier for the rate determining step, leading to high catalytic activity.

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.

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

Electrochemical N2 reduction reactions (NRR) and the N2 oxidation reaction (NOR), using H2 O 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 mgcat. -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 mgcat. -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.

Catalytic Kinetics Regulation for Enhanced Electrochemical Nitrogen Oxidation by Ru-Nanoclusters-Coupled Mn3 O4 Catalysts Decorated with Atomically Dispersed Ru Atoms.

Electrochemical N2 oxidation reaction (NOR), using water and N2 in the atmosphere, represents a sustainable approach for nitric production to replace the conventional industrial synthesis with high energy consumption and greenhouse gas emission. Meanwhile, owing to chemical inertness of N2 and sluggish kinetics for 10-electron transfer, emerging electrocatalysts remain largely underexplored. Herein, Ru-nanoclusters-coupled Mn3 O4 catalysts decorated with atomically dispersed Ru atoms (Ru-Mn3 O4 ) are designed and explored as an advanced electrocatalyst for ambient N2 oxidation, with an excellent Faraday efficiency (28.87%) and a remarkable NO3 - yield (35.34 µg h-1 mg-1 cat. ), respectively. Experiments and density functional theory calculations reveal that the outstanding activity is ascribed to the coexistence of Ru clusters and single-atom Ru. The synergistic effect between the Ru clusters and Mn3 O4 can effectively activate the chemically inert N2 , lowering the kinetic barrier for the vital breakage of N≡N. The intensive *OH supply and enhanced conductivity are used to regulate the catalytic kinetics for optimized performance. This work provides brand-new ideas for the rational design of electrocatalysts in complicated electrocatalytic reactions with multiple dynamics-different steps.

Targeted Assembly of Ultrathin NiO/MoS2 Electrodes for Electrocatalytic Hydrogen Evolution in Alkaline Electrolyte.

The development of non-noble metal catalysts for hydrogen revolution in alkaline media is highly desirable, but remains a great challenge. Herein, synergetic ultrathin NiO/MoS2 catalysts were prepared to improve the sluggish water dissociation step for HER in alkaline conditions. With traditional electrode assembly methods, MoS2:NiO-3:1 exhibited the best catalytic performance; an overpotential of 158 mV was required to achieve a current density of 10 mA/cm2. Further, a synergetic ultrathin NiO/MoS2/nickel foam (NF) electrode was assembled by electrophoretic deposition (EPD) and post-processing reactions. The electrode displayed higher electrocatalytic ability and stability, and an overpotential of only 121 mV was needed to achieve a current density of 10 mA/cm2. The improvement was ascribed to the better catalytic environment, rather than a larger active surface area, a higher density of exposed active sites or other factors. DFT calculations indicated that the hybrid NiO/MoS2 heterostuctured interface is advantageous for the enhanced water dissociation step and the corresponding lower kinetic energy barrier-from 1.53 to 0.81 eV.

Boosting electrocatalytic reduction of nitrogen to ammonia under ambient conditions by alloy engineering.

Electrochemical reduction of nitrogen to ammonia under ambient conditions is regarded as a potential approach to tackle the energy-intensive Haber-Bosch process. However, it usually suffers from extremely low ammonia yield and faradaic efficiency due to the lack of highly active and selective electrocatalysts. Herein, fusiform-like ruthenium-copper alloy nanosheets (RuCu-FNs) were prepared by alloy engineering and utilized for the electrocatalytic NRR under ambient conditions. A high FE of 7.2% and an NH3 yield rate of 53.6 µg h-1 mgcat-1 were achieved at -0.1 V vs. RHE, which were better than those of the corresponding non-metallic catalyst and most alloy catalysts. The superior performance was ascribed to the differentiated second catalytic site for achieving both effectively adsorptive activation of chemically inert N2 and intermediate desorption from the catalyst surface. The source of NH3 was also identified with isotopic labeling via a self-developed simple and economic pathway. We provided a feasible pathway for the rational design of electrocatalysts for artificial N2 fixation.

Selective electroreduction of dinitrogen to ammonia on a molecular iron phthalocyanine/O-MWCNT catalyst under ambient conditions.

Effective catalysts with sufficient activity and selectivity are essential for the nitrogen reduction reaction (NRR). Many fruitful NRR electrocatalysts have been investigated with regard to NH3 production under ambient conditions in recent years. However, well-defined and modifiable molecular catalysts have rarely been reported for the NRR to date. Here, molecular FePc was grafted on an O-MWCNT surface as a NRR electrocatalyst to improve its recyclability. This catalyst displayed high electrocatalytic ability and selectivity, giving a large NH3 yield of 36 µg h-1 mg-1 cat., a FE of 9.73% and a turnover number (TON) of 12.56 after 2 h of electrocatalytic reaction in an acidic electrolyte, superior to most of the reported materials. DFT calculations indicated that the NRR preferentially proceeded along the alternate pathway, the activation of N2 to produce N2H* is the rate-limiting step with a ΔG value of 1.79 eV. Conclusively, we report FePc/O-MWCNT as a low-cost, high-efficiency NRR catalyst that also offers a valuable reference for molecular electrocatalyst research in electrochemical nitrogen reduction.