Alloying-Induced Asymmetrical Pd Sites Enabling Efficient and Durable Formic Acid Dehydrogenation

Abstract Developing Pd-based catalysts for formic acid (HCOOH) dehydrogenation is of great significance to the advancement of renewable hydrogen utilization. However, traditional Pd surfaces typically display symmetrical electronic and geometrical configurations that suffer from both selectivity issues and CO poisoning phenomena, deteriorating their long-term HCOOH dehydrogenation performance. In this study, we report a bismuth–palladium (BiPd) alloy catalyst with asymmetric electronic and geometric Pd sites that achieved an exceptional H2-evolving turnover frequency (5893.7 h–1) of HCOOH dehydrogenation while maintaining over 96% catalytic activities spanning consecutive 15-round experiments. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and synchrotron X-ray absorption spectroscopy (XAS) characterizations verified the successful construction of BiPd alloys and that Bi components desymmetrized the electronic configuration of Pd sites toward the thermodynamically favored HCOOH dehydrogenation pathway for H2 evolution. On the other hand, in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) and kinetic isotope effect experiments combined with density functional theory (DFT) calculations collectively demonstrated that Bi also diluted Pd ensembles, and the resulting asymmetric Pd architectures reduced the diversity of *CO adsorption configurations on the surface of BiPd alloys, effectively mitigating CO poisoning. This work underscores the critical role of alloying engineering in designing Pd-based catalysts for practically implementing sustainable hydrogen release from liquid organic hydrogen carriers.