Constructing a CoO-CuOx heterostructure for efficient electrochemical reduction of nitrate to ammonia

The electrochemical nitrate reduction reaction (NtrRR) represents a sustainable approach to realize the green synthesis of ammonia, yet developing efficient electrocatalysts to improve the sluggish reaction kinetics and the undesirable selectivity towards NH3, while simultaneously suppressing the hydrogen evolution reaction (HER), is critical. Herein, we report a CoO-CuOx heterostructure catalyst that is prepared by in situ growing Cu(OH)(2) nanoarrays on Cu foam (CF), followed by hydrothermal treatment in the presence of a Co salt. Multiple characterizations revealed that a well-defined heterostructure with a distinct interface is formed between the CoO and CuOx phases. In the NtrRR test, the CoO-CuOx/CF catalyst displayed a high NH3 selectivity of 94.29%, an NH3 faradaic efficiency (FENH3) of 92.15%, and a high NH3 yield rate of 0.510 mmol h(-1) cm(-2). Also, the heterostructure catalyst had remarkable catalytic stability, evidenced by the negligible FENH3 decay after four consecutive cycling tests. This excellent catalytic performance is attributed to the fact that the interfaces in the CuOx and CoO heterostructure can facilitate the electron transfer, hence improving the reaction kinetics. This study offers a generic strategy for preparing efficient and durable electrocatalysts toward the NtrRR and other multiple electron/proton-involved electrocatalytic reactions.