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

The electrocatalytic reduction of sulfur dioxide (SO2) to hydrogen sulfide (H2S) is a promising strategy for efficient sulfur resource utilization. Copper (Cu) catalysts show high selectivity for SO2 reduction, but their limited hydrogenation capacity restricts H2S production. Palladium (Pd), known for its hydrogenation efficiency, was incorporated to overcome this limitation. We synthesized CuPd bimetallic catalysts to enhance hydrogenation efficiency in SO2 electroreduction. Among these, Cu67Pd33 exhibited superior catalytic performance, achieving a H2S 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 *H2S. The synergistic catalysis between Cu and Pd ensures efficient transformation of intermediates and facilitates the conversion of SO2 to H2S. This study highlights a novel strategy for enhancing hydrogenation in SO2 electroreduction and provides insights into the synergistic mechanisms of CuPd bimetallic catalysts, emphasizing the critical role of interfacial interactions in catalytic performance.