H-Embedding Induced Electron Localization in Pd Lattice for Improving Electrochemical Hydrogen Purification.

Abstract

Electrochemical hydrogen purification (EHP) technology with high-efficiency and easy-operation holds great potential in blended hydrogen transportation, which is currently restricted to proton exchange membrane system and Pt-based catalysts. As promising candidates used in alkaline anion exchange membrane system, Pd-based catalysts are hampered by the intense interaction between H^* and delocalized 4d electrons, resulting in unsatisfactory catalytic activity. In this study, a marked enhancement of the alkaline membrane-based EHP performance is achieved, with hydrogen purity up to 99.96% separated from a CH₄-H₂ mixture, by strategically incorporating interstitial H atoms into Pd lattices for improving the anodic hydrogen oxidation reaction. Detailed characterizations and density functional theory calculations elucidate that the presence of interstitial H localizes free electrons into Pd-H covalent bonds, thereby weakening the interaction between surface-adsorbed H^* and the catalytic surface. Moreover, operando spectroscopies and ab initio molecular dynamic simulations reveal that the enhanced interaction between the catalyst surface and interfacial water by electron delocalization, facilitates the desorption of H^* to the interfacial water layer during catalysis. This research highlights the pivotal role of electronic localization in modulating the adsorption strength of key reaction intermediates for the design of efficient Pd-based catalysts.