Metal−Support Interactions at the Pd/In ₂ O ₃ Interface Enhance CO ₂ Electroreduction

Metal−support interactions are central to heterogeneous catalysis, however, their role in influencing active sites under electrocatalytic conditions is not fully understood. Here, we show that Pd/In2O3 exhibits enhanced Faradaic efficiency and partial current density for formic acid production relative to In2O3. Operando attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy reveals accelerated CO2 activation on Pd/In2O3 through enhanced formation and conversion of formate intermediates. X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) provide evidence consistent with the possible formation of Pd-In alloy species during electrocatalysis. Interpretable machine learning-derived descriptors and adhesion energy analysis further suggest that such metal−support alloying arises from a thermodynamic preference for Pd-In over In-In bonding at the interface. Density functional theory (DFT) further indicates that Pd-In alloy sites lower the energy barrier for formate formation compared with In2O3. This decrease originates from enhanced hybridization between Pd 4d and C 2p orbitals at the Pd-In alloy surface, stabilized through metal−support interactions. These findings advance the mechanistic understanding of metal−support interactions in electrocatalysis and provide a strategy for designing catalysts with highly active metal sites.