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.