Histidine-Based "Transfer Stations" at Carbon-Immobilized Metal Particles Enable Rapid Hydrogen Transfer for Efficient Formic Acid Dehydrogenation.

The interaction of surface metal species with the solution plays a key role in engineering heterogeneous catalytic processes. Herein, we present the facile synthesis of L-histidine-coordinated PdAg nanoparticles (4.03 ± 0.08 nm) anchored on pristine carbon supports (denoted as PdAg-NH2/C) and their use for formic acid dehydrogenation (FAD). Significant acceleration of FAD related to the histidine is observed, and the enhancement mechanism is experimentally and theoretically investigated. The presence of L-histidine at metal sites promotes rapid binding of formic acid molecules due to acid-base interactions. The local enrichment of both proton and formate at the metal-solution interfaces promotes the subsequent formate decomposition and hydride transfer to the metal surface. The as-generated surface H species are more concentrated compared to the previously reported catalyst where the metal is loaded on an amino-modified support, this enabling a significantly enhanced H2 production. The optimal Pd1Ag1-NH2/C catalyst exhibits a high turnover frequency of 6493.5 h-1 at 333 K based on the total amount of Pd, together with a H2 selectivity of 100%. This study emphasizes the critical role of optimizing local transport pathways near catalytic centers chemically and further provide insights to the rational development of heterogeneous catalysts for FAD technologies.