Ambient electrochemical N ₂ -to-NH ₃ fixation enabled by Nb ₂ O ₅ nanowire array

Electrochemical reduction offers a carbon-neutral process for energy-saving NH ₃ synthesis under ambient conditions, but this process involves difficulty in breaking the strong NN bond of inert N ₂ and the challenge of N ₂ activation, underlining the need for high-performance electrocatalysts for the nitrogen reduction reaction (NRR). Herein, we report our recent effort in this direction by in situ hydrothermally growing a Nb ₂ O ₅ nanowire array on carbon cloth (Nb ₂ O ₅ /CC) as a self-standing NRR catalyst electrode toward artificial N ₂ fixation with high selectivity under ambient conditions. In 0.1 M Na ₂ SO ₄ , such Nb ₂ O ₅ /CC achieves an NH ₃ formation rate of 1.58 × 10 ^-10 mol s ^-1 cm ^-2 and a high faradaic efficiency of 2.26% at -0.60 V, rivaling the performances of most reported non-noble metal NRR electrocatalysts in neutral medium. Notably, this catalyst also shows high electrochemical stability during electrolysis and recycling tests. Density functional theory calculations reveal that a distal associative route is involved in the reaction pathways during the NRR over the Nb ₂ O ₅ (001) facet. This work would open up an exciting new avenue to explore the design of self-standing 3D electrodes made of transition metal oxides for the NRR and other applications.