Ambient electrochemical N2-to-NH3 fixation enabled by Nb2O5 nanowire array

Abstract

Electrochemical reduction offers a carbon-neutral process for energy-saving NH₃ synthesis under ambient conditions, but this process involves difficulty in breaking the strong NN bond of inert N₂ and the challenge of N₂ 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 Nb₂O₅ nanowire array on carbon cloth (Nb₂O₅/CC) as a self-standing NRR catalyst electrode toward artificial N₂ fixation with high selectivity under ambient conditions. In 0.1 M Na₂SO₄, such Nb₂O₅/CC achieves an NH₃ 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 Nb₂O₅ (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.