Palladium-copper nanodot as novel H2-evolution cocatalyst: Optimizing interfacial hydrogen desorption for highly efficient photocatalytic activity

Noble metal palladium (Pd) is well-known as excellent photocatalytic cocatalyst, but its strong adsorption to hydrogen causes its limited H2-evolution activity. In this study, the transition metal Cu was successfully introduced into the metallic Pd to weaken its hydrogen-adsorption strength to improve its interfacial H2-evolution rate via the Pd-Cu alloying effect. Herein, the ultrasmall Pd100−xCux alloy nanodots (2−5 nm) as a novel H2-evolution cocatalyst were integrated with the TiO2 through a simple NaH2PO2-mediated co-deposition route. The resulting Pd100−xCux/TiO2 sample shows the significantly enhanced photocatalytic H2-generation performance (269.2 μmol h−1), which is much higher than the bare TiO2. Based on in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and density functional theory (DFT) results, the as-formed Pd100−xCux alloy nanodots can effectively promote the separation of photo-generated charges and weak the adsorption strength for hydrogen to optimize the process of hydrogen-desorption process on Pd75Cu25 alloy, thus leading to high photocatalytic H2-evolution activity. Herein, the weakened H adsorption of Pd75Cu25 cocatalyst can be ascribed to the formation of electron-rich Pd after the introduction of weak electronegativity Cu. The present work about optimizing electronic structure for promoting interfacial reaction activity provides a new sight for the development of the highly efficient photocatalysts.