Support-Dependent Formic Acid Dehydrogenation over Pd-Supported Catalysts Induced by Hydrogen Spillover

Dehydrogenation of formic acid involves the formation of hydrogen atoms and their subsequent recombination. This suggests that hydrogen spillover through the support materials may significantly impact the catalytic activity of Pd-supported catalysts. Controlled synthesis using deposition–precipitation produces Pd nanoparticles with nearly identical average sizes impregnated onto various support materials (CeO2, TiO2, carbon, ZrO2, Al2O3), each exhibiting different hydrogen spillover capabilities. The reaction rates of formic acid dehydrogenation follow the order of generally accepted hydrogen spillover capabilities (CeO2 ≥ TiO2 > carbon > Al2O3 ≈ ZrO2). Moreover, the catalyst with a higher hydrogen spillover capability has a lower activation barrier, indicating that the hydrogen spillover is highly relevant to the rate-limiting step. Even a few support-specific behaviors, such as the inverse activity order induced by surface area effects (Pd/Al2O3, Pd/ZrO2) and the rapid deactivation of Pd/CeO2 and Pd/TiO2, further highlight that hydrogen spillover plays a key role in formic acid dehydrogenation.