Xiaoya Fan

Abstract Renewable electricity‐powered nitrate/carbon dioxide co‐reduction reaction toward urea production paves an attractive alternative to industrial urea processes and offers a clean on‐site approach to closing the global nitrogen cycle. However, its large‐scale implantation is severely impeded by challenging C–N coupling and requires electrocatalysts with high activity/selectivity. Here, cobalt‐nanoparticles anchored on carbon nanosheet (Co NPs@C) are proposed as a catalyst electrode to boost yield and Faradaic efficiency (FE) toward urea electrosynthesis with enhanced C–N coupling. Such Co NPs@C renders superb urea‐producing activity with a high FE reaching 54.3% and a urea yield of 2217.5 µg h −1 mg cat. −1 , much superior to the Co NPs and C nanosheet counterparts, and meanwhile shows strong stability. The Co NPs@C affords rich catalytically active sites, fast reactant diffusion, and sufficient catalytic surfaces‐electrolyte contacts with favored charge and ion transfer efficiencies. The theoretical calculations reveal that the high‐rate formation of *CO and *NH 2 intermediates is crucial for facilitating urea synthesis.

NH3 is an essential feedstock for fertilizer synthesis. Industry-scale NH3 synthesis mostly relies on the Haber-Bosch method, however, which suffers from massive CO2 emission and high energy consumption. Electrocatalytic NO3− reduction is an attractive substitute to the Haber-Bosch method for synthesizing NH3 under mild conditions. As this reaction will produce a variety of products, it highly desires efficient and selective electrocatalyst for NH3 generation. Here, we report in situ grown Fe3O4 particle on stainless steel (Fe3O4/SS) as a high-efficiency electrocatalyst for NO3− reduction to NH3. In 0.1 M NaOH with 0.1 M NaNO3, such Fe3O4/SS reaches a remarkable Faradaic efficiency of 91.5% and a high NH3 yield of 10,145 µg·h−1·cm−2 at −0.5 V vs. reversible hydrogen electrode (RHE). Furthermore, it owns robust structural and electrochemical stability. This work provides useful guidelines to expand the scope of metallic oxide electrocatalysts for NH3 synthesis. The catalytic mechanism is uncovered and discussed further by theoretical calculations.

Abstract Electrochemical nitrate (NO 3 − ) reduction reaction (NO 3 − RR) is a potential sustainable route for large‐scale ambient ammonia (NH 3 ) synthesis and regulating the nitrogen cycle. However, as this reaction involves multi‐electron transfer steps, it urgently needs efficient electrocatalysts on promoting NH 3 selectivity. Herein, a rational design of Co nanoparticles anchored on TiO 2 nanobelt array on titanium plate (Co@TiO 2 /TP) is presented as a high‐efficiency electrocatalyst for NO 3 − RR. Density theory calculations demonstrate that the constructed Schottky heterostructures coupling metallic Co with semiconductor TiO 2 develop a built‐in electric field, which can accelerate the rate determining step and facilitate NO 3 − adsorption, ensuring the selective conversion to NH 3 . Expectantly, the Co@TiO 2 /TP electrocatalyst attains an excellent Faradaic efficiency of 96.7% and a high NH 3 yield of 800.0 µmol h −1 cm −2 under neutral solution. More importantly, Co@TiO 2 /TP heterostructure catalyst also presents a remarkable stability in 50‐h electrolysis test.

Abstract Ammonia (NH 3 ) is an indispensable feedstock for fertilizer production and one of the most ideal green hydrogen rich fuel. Electrochemical nitrate (NO 3 − ) reduction reaction (NO 3 − RR) is being explored as a promising strategy for green to synthesize industrial‐scale NH 3 , which has nonetheless involved complex multi‐reaction process. This work presents a Pd‐doped Co 3 O 4 nanoarray on titanium mesh (Pd‐Co 3 O 4 /TM) electrode for highly efficient and selective electrocatalytic NO 3 − RR to NH 3 at low onset potential. The well‐designed Pd‐Co 3 O 4 /TM delivers a large NH 3 yield of 745.6 µmol h −1 cm −2 and an extremely high Faradaic efficiency (FE) of 98.7% at −0.3 V with strong stability. These calculations further indicate that the doping Co 3 O 4 with Pd improves the adsorption characteristic of Pd‐Co 3 O 4 and optimizes the free energies for intermediates, thereby facilitating the kinetics of the reaction. Furthermore, assembling this catalyst in a Zn‐NO 3 − battery realizes a power density of 3.9 mW cm −2 and an excellent FE of 98.8% for NH 3 .