Active hydrogen boosts electrochemical nitrate reduction to ammonia

Electrochemical nitrate reduction to ammonia is a promising alternative strategy to the traditional Haber-Bosch process but suffers from a low Faradaic efficiency and limited ammonia yield due to the sluggish multi-electron/proton-involved steps. Herein, we report a typical hollow cobalt phosphide nanosphere electrocatalyst assembled on a self-supported carbon nanosheet array synthesized with a confinement strategy that exhibits an extremely high ammonia yield rate of 8.47 mmol h(-1) cm(-2) through nitrate reduction reaction, which is highly superior to previously reported values to our knowledge. In situ experiments and theoretical investigations reveal that the dynamic equilibrium between the generation of active hydrogen on cobalt phosphide and its timely consumption by nitrogen intermediates leads to a superior ammonia yield with a high Faradaic efficiency. This unique insight based on active hydrogen equilibrium provides new opportunities for large-scale ammonia production through electrochemical techniques and can be further used for carbon dioxide capture. While electrochemical conversion of nitrate to ammonia offers a renewable means to remediate waste compounds, it is challenging to achieve selective catalysis. Here, authors demonstrate a strategy to improve electrocatalytic ammonia production using cobalt phosphide on carbon nanosheet arrays.

Automated summary

This study presents a hollow cobalt phosphide nanosphere electrocatalyst assembled on a self-supported carbon nanosheet array for electrochemical nitrate reduction to ammonia. The catalyst exhibits an extremely high ammonia yield rate and a high Faradaic efficiency, achieved through the dynamic equilibrium between the generation of active hydrogen and its consumption by nitrogen intermediates. This insight provides new opportunities for large-scale ammonia production and carbon dioxide capture through electrochemical techniques.