Highly selective electrocatalytic reduction of nitrate to ammonia over a copper–cobalt bimetallic catalyst†

Abstract

The electrocatalytic nitrate reduction reaction (NitRR) is a promising alternative to the traditional Haber–Bosch process. However, the competitive hydrogen evolution reaction results in poor NH₃ selectivity (S_NH3). Here, a Cu–Co bimetallic catalyst supported on biomass-derived porous carbon (Cu–Co/BPC) is designed and synthesized. Interestingly, the catalyst presents a high NH₃ yield rate of 9114.1 ± 244.8 μg h⁻¹ cm⁻² at −1.4 V (vs. RHE) and a high faradaic efficiency (FE) of 84.5 ± 1.6% at −1.0 V (vs. RHE). Notably, the S_NH3 of Cu–Co/BPC catalyst is kept above 94.2% under a broad range from −1.0 to −1.4 V (vs. RHE), indicating the high NitRR-to-NH₃ selectivity of Cu–Co/BPC. The combination of in situ characterization and experimental results indicates that the electron transfer occurs between Cu and Co, and many active sites are generated for adsorption and activation of NO double bonds, and hydrogenation reactions occur with adjacent H protons to improve the selectivity of NH₃.