Interface Engineering in Cu-CoO Heterostructure for High-Efficiency Electrocatalytic Nitrate Reduction to Ammonia

Abstract

The electrocatalytic nitrate (NO3⁻) reduction reaction (NtrRR) to synthesize ammonia (NH3) presents a promising alternative to the traditional Haber-Bosch process, owing to its mild reaction conditions and sustainability. Herein, we successfully synthesized a Cu-CoO@CNT heterostructure catalyst for electrochemical NO3⁻-to-NH3 conversion. As a result, the as-synthesized Cu-CoO@CNT exhibits a superior electrocatalytic activity with a high NH3 production rate of 83.2 ± 1.7 mg h−1 mgcat.−1 at −0.9 V (vs. RHE). The FE of NH3 formation can reach the maximum value of 98.1 ± 1.5% at −0.6 V (vs. RHE), and excellent Faradaic efficiency (FE) of NH3 over 92% is under a broad range from −0.2 to −0.6 V (vs. RHE). Characterization results of Cu-CoO@CNT before and after the NtrRR demonstrate that Cu spontaneously transfers electrons to Co through the heterojunction interface during the catalytic process. This electron transfer-induced structural transition stabilizes Cu in the highly active +2 valence state, thereby enabling it to maintain strong adsorption of reaction intermediates throughout NtrRR. This work provides new insights for designing high-performance catalysts for nitrate reduction to ammonia.