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

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 (<i>S</i> _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 (<i>vs.</i> RHE) and a high faradaic efficiency (FE) of 84.5 ± 1.6% at -1.0 V (<i>vs.</i> RHE). Notably, the <i>S</i> _NH₃ of Cu-Co/BPC catalyst is kept above 94.2% under a broad range from -1.0 to -1.4 V (<i>vs.</i> RHE), indicating the high NitRR-to-NH₃ selectivity of Cu-Co/BPC. The combination of <i>in situ</i> 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 N[double bond, length as m-dash]O double bonds, and hydrogenation reactions occur with adjacent H protons to improve the selectivity of NH₃.