Interfacial water activation by Pd promotes SO2 electroreduction to H2S on CuPd bimetallic catalysts

The electrocatalytic reduction of sulfur dioxide (SO 2 ) to hydrogen sulfide (H 2 S) is a promising strategy for efficient sulfur resource utilization. Copper (Cu) catalysts show high selectivity for SO 2 reduction, but their limited hydrogenation capacity restricts H 2 S production. Palladium (Pd), known for its hydrogenation efficiency, was incorporated to overcome this limitation. We synthesized CuPd bimetallic catalysts to enhance hydrogenation efficiency in SO 2 electroreduction. Among these, Cu 67 Pd 33 exhibited superior catalytic performance, achieving a H 2 S partial current density of 201.56 mA·cm −2 (1.08 mmol·cm −2 ·h −1 ), a 120 % increase over Cu and 154 % over Pd. In-situ Fourier-transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations revealed that Cu primarily catalyzes the reduction of *SOH to *S, while Pd facilitates the activation and dissociation of interfacial water to provide hydrogen and reduces the energy barrier for the conversion of *S to *H 2 S. The synergistic catalysis between Cu and Pd ensures efficient transformation of intermediates and facilitates the conversion of SO 2 to H 2 S. This study highlights a novel strategy for enhancing hydrogenation in SO 2 electroreduction and provides insights into the synergistic mechanisms of CuPd bimetallic catalysts, emphasizing the critical role of interfacial interactions in catalytic performance.