Insights into Electrocatalytic Nitrate Reduction to Ammonia via Cu-Based Bimetallic Catalysts

Cu-based bimetallic catalysts have been studied in the electrocatalytic nitrate (NO3–) reduction reaction (NO3–RR) for a long time. However, few studies have focused on horizontal comparison of CuNi, CuCo, and CuFe (abbreviated as CuM) bimetallic catalysts in electrocatalytic NO3–RR for ammonia synthesis. Herein, we prepare the three series of Cu-based bimetallic catalysts, with different atom ratios of Cu/M (Cu/M = 7/3, 5/5, or 3/7) and ordered mesoporous carbon (OMC) as support (denoted as CuM/OMC). The characterization results reveal that the metallic particles of Cu and M components possess an intimate relationship on the CuM/OMC catalysts. The electrocatalytic NO3–RR performance uncovers that the optimal NH3 yield rates of CuM/OMC catalysts at −0.8 V (vs reversible hydrogen electrode (RHE)) follow this order: Cu5Fe5/OMC > Cu5Co5/OMC > Cu7Ni3/OMC > Cu/OMC > Fe/OMC > Co/OMC > Ni/OMC > OMC. The bimetallic CuM/OMC catalysts exhibit higher NH3 yield rates than the monometallic catalysts. This is attributed to strong synergistic effects between the Cu and M components. We expect that these insights can stimulate new developments of bimetallic catalysts in electrocatalysis.