Regulating Electron–Hole Separation to Promote Photocatalytic H₂ Evolution Activity of Nanoconfined Ru/MXene/TiO₂ Catalysts

Abstract

A facile strategy for the preparation of a nanoconfined Ti₃C₂/Ru cocatalyst by direct reduction of Ru³⁺ ions without an additional reductant was developed. The <i>in situ</i> formation of TiO₂ nanosheets on the Ti₃C₂/Ru surface ensures the separation of the semiconductor and cocatalyst (TiO₂-Ti₃C₂/Ru), resulting in charge segregation and migration more effective than those achieved by traditionally prepared Ru-TiO₂-Ti₃C₂. Owing to its low Fermi level, the self-assembled Ti₃C₂/Ru cocatalyst accepted the photogenerated electrons and promoted H₂ evolution without an induction period, while exhibiting high surface structure stability. The changes in the work function and surface terminations of Ti₃C₂ during the photocatalysis were revealed by DFT calculations and <i>in situ</i> diffuse reflectance infrared Fourier transform spectroscopy. The efficient electron transfer enabled by the structurally separated Ti₃C₂/Ru-based photocatalyst significantly reduced the electron-hole recombination, increasing the photocatalytic H₂ evolution activity. This work provides a guiding design approach for future solar energy conversion with the semiconductor-cocatalyst system.