Enrichment of Active Hydrogen at Amorphous CoO/Cu2O 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 (NO3RR) 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/Cu2O tandem catalyst provides sufficient active hydrogen and synergistically catalyzes the NO3RR. The a-CoO/Cu2O catalyst showed excellent performance with a maximum NH3 Faradaic efficiency of 95.72% and a maximum yield rate of 0.96 mmol h-1 mgcat-1 at -0.4 V. In the flow cell, the maximum NH3 yield rate of 12.14 mmol h-1 mgcat-1 is achieved at -800 mA. The high NO3RR activity of a-CoO/Cu2O is attributed to the synergistic cascade effect of amorphous CoO and Cu2O at the heterojunction interface, where Cu2O serves as the adsorption site for NO3-, 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 NO3RR.