Enhancing electrochemical nitrate reduction toward dinitrogen selectivity on Sn-Pd bimetallic electrodes by surface structure design

Bimetallic palladium (Pd) and tin (Sn) catalysts were electrochemically deposited on stainless steel mesh support by controlling the metal deposition sequence, total electrical charge, and metal composition. Results showed that the preparation procedure affected the crystal structure of bimetallic Pd-Sn catalysts, which significantly influenced nitrate removal efficiency and dinitrogen selectivity. Electrode with Sn on the outside surface exhibited relatively greater nitrate removal rate constant and nitrate conversion. The Sn to Pd molar ratio and the electrical charge applied during electrode preparation also affected the nitrate reduction performance. The SS/Sn0.2Pd0.8-497 electrode exhibited 88, 89, 79, and 9% of total nitrate removal, dinitrogen selectivity, dinitrogen yield, and NH4+ selectivity, respectively. Among the three major facets, (214), (131) and (420) of Sn3Pd alloy on the electrode surface, (420) exhibited the most critical effect on the dinitrogen yield. Crystal structure of catalysts controls the reactivity and selectivity of electrochemical reduction as exemplified by nitrate.