Pd-PdO Interface as Active Site for HCOOH Selective Dehydrogenation at Ambient Condition

Splitting HCOOH (FA) into H₂ and CO₂ with high turnover frequencies and selectivity is highly desirable for H₂ generation and its facilitated utilization. However, the mostly adopted Pd based metallic catalysts severely suffered from low catalytic efficiency and self-poisoning, owning to the FA dehydration side reaction. Here, we demonstrate first that the secret for developing highly active and selective Pd toward FAD lies in building abundant Pd-PdO interfaces at the catalytic surface. Using a chemical blocking technique, we identify surface Pd(0) as the active sites for FA adsorption. By combining the density functional theoretical calculations, experiments, and in situ sensitive probes, PdO is found to be active in fastening the dehydrogenation rate through pulling hydrogen from the reaction intermediates, as well as overcomes CO poisoning by eliminating the self-poisoning dehydration route. Moreover, tetragonal phase PdO/C with minor Pd(0) at the surface is discovered as highly efficient antipoisoning FAD catalysts for the first time, with the highest H₂ generation rate per unit mass of Pd ever reported (8.72 mol H₂ g^-1_Pd h^-1) at ambient temperature, indicating a power density of 304 W g^-1_Pd (at 0.65 V) in PEMFC. Our finding is applicable in explaining the catalytic performance variation of Pd based composite catalysts, and the synergy at the interface allows for further development of FAD catalysts based on Pd and other transitional catalysts.