Atomic Insights into Robust Pt-PdO Interfacial Site-Boosted Hydrogen Generation

Abstract

Suppression of catalyst deactivation without compromising activity has been a long-standing yet elusive goal in heterogeneous catalysis. Herein, we report a remarkable achievement of both hydrogen generation activity and durability by atomically engineering Pt–PdO interfacial sites. A combination of kinetics (isotopic) analyses, multiple characterization techniques, molecular dynamics, and density functional theory calculations was employed to reveal the evolution of the Pt–Pd atomic structure where Pd segregates to the outer surface of Pt nanoparticles, followed by partial oxidation, resulting in the structure of a Pt-rich core and a PdO–Pd-rich shell. The strong capability of PdO to activate H2O compensates for its adverse effects on Pt electronic properties and creates the Pt and PdO interfacial sites for ammonia borane and H2O activation, respectively. Moreover, because of the strong electron repulsion and steric hindrance effects, these surface PdO sites strongly inhibit the adsorption of B(OH)4–, thus protecting Pt active sites from poisoning. As a result, such a unique atomic structure with a Pt–Pd ratio of 1:1 is found to be the most promising catalyst at the apex of the volcano curve. The strategy developed here unambiguously clarifies the activity and durability attributes of Pt–PdO interfacial sites for this reaction and sheds light on the design of a new type of highly active yet stable metal catalysts.