Regulating Electron-Hole Separation to Promote Photocatalytic H Evolution Activity of Nanoconfined Ru/MXene/TiO Catalysts.

A facile strategy for the preparation of a nanoconfined TiC/Ru cocatalyst by direct reduction of Ru ions without an additional reductant was developed. The formation of TiO nanosheets on the TiC/Ru surface ensures the separation of the semiconductor and cocatalyst (TiO-TiC/Ru), resulting in charge segregation and migration more effective than those achieved by traditionally prepared Ru-TiO-TiC. Owing to its low Fermi level, the self-assembled TiC/Ru cocatalyst accepted the photogenerated electrons and promoted H evolution without an induction period, while exhibiting high surface structure stability. The changes in the work function and surface terminations of TiC during the photocatalysis were revealed by DFT calculations and diffuse reflectance infrared Fourier transform spectroscopy. The efficient electron transfer enabled by the structurally separated TiC/Ru-based photocatalyst significantly reduced the electron-hole recombination, increasing the photocatalytic H evolution activity. This work provides a guiding design approach for future solar energy conversion with the semiconductor-cocatalyst system.