Ultrathin nanosheets of palladium in boosting its cocatalyst role and plasmonic effect towards enhanced photocatalytic hydrogen evolution

The combination of a metal with a semiconductor is a promising route to improve the solar-to-chemical conversion efficiency of photocatalysts. In this article, ultrathin Pd nanosheets are integrated with semiconductor TiO2 nanosheets for photocatalytic hydrogen evolution, which acts as a cocatalyst and plasmonic agent in ultraviolet and visible-near-infrared spectral regions, respectively. Owing to the unique two-dimensional (2D) nanostructure, the Pd nanosheet cocatalyst realizes the large TiO2–Pd interfacial area for electron transfer as well as a large Pd exposed area for reduction reactions, while the plasmonic Pd nanosheets offer strong vis-NIR light absorption for “hot” electron production as well as a large interfacial area for “hot” electron injection. As a result, the Pd nanosheets achieve improved photocatalytic activity in comparison with three-dimensional Pd nanotetrahedrons under both light irradiations. This work underlines the importance in choosing a suitable shape of metal in the surface and interface design of semiconductor–metal hybrid photocatalysts as well as the advantages of 2D metal nanostructures in realizing high photocatalytic performance.