Enrichment of Active Hydrogen at Amorphous CoO/CuO Heterojunction Interfaces Enhances Electrocatalytic Nitrate Reduction to Ammonia.

The reduction of nitrate into valuable ammonia via electrocatalysis offers a green and sustainable synthetic pathway for ammonia. The electrocatalytic nitrate reduction reaction (NORR) encompasses two crucial reaction steps: nitrate deoxygenation and nitrite hydrogenation. Notably, the nitrite hydrogenation reaction is regarded as the rate-determining step of the process. Herein, the amorphous CoO support introduced for the construction of the a-CoO/CuO tandem catalyst provides sufficient active hydrogen and synergistically catalyzes the NORR. The a-CoO/CuO catalyst showed excellent performance with a maximum NH Faradaic efficiency of 95.72% and a maximum yield rate of 0.96 mmol h mg at -0.4 V. In the flow cell, the maximum NH yield rate of 12.14 mmol h mg is achieved at -800 mA. The high NORR activity of a-CoO/CuO is attributed to the synergistic cascade effect of amorphous CoO and CuO at the heterojunction interface, where CuO serves as the adsorption site for NO , while the accelerated active hydrogen generation of amorphous CoO promotes the nitrite hydrogenation reaction. This work provides a strategy for designing multi-site cascade catalysts centered on amorphous structures to achieve efficient NORR.