Enrichment of Active Hydrogen at Amorphous CoO/Cu2O Heterojunction Interfaces Enhances Electrocatalytic Nitrate Reduction to Ammonia

Abstract The reduction of nitrate into valuable ammonia via electrocatalysis offers a green and sustainable synthetic pathway for ammonia. The electrocatalytic nitrate reduction reaction (NO 3 RR) 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/Cu 2 O tandem catalyst provides sufficient active hydrogen and synergistically catalyzes the NO 3 RR. The a‐CoO/Cu 2 O catalyst showed excellent performance with a maximum NH 3 Faradaic efficiency of 95.72% and a maximum yield rate of 0.96 mmol h −1 mg cat −1 at −0.4 V. In the flow cell, the maximum NH 3 yield rate of 12.14 mmol h −1 mg cat −1 is achieved at −800 mA. The high NO 3 RR activity of a‐CoO/Cu 2 O is attributed to the synergistic cascade effect of amorphous CoO and Cu 2 O at the heterojunction interface, where Cu 2 O serves as the adsorption site for NO 3 − , 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 NO 3 RR.