Near Bandgap Excitation Inhibits the Interfacial Electron Transfer of Semiconductor/Cocatalyst.

Understanding the ultrafast interfacial electron transfer (IET) process is essential for establishing the structure-property relationship of the semiconductor/cocatalyst system for photocatalytic H2 evolution. However, the IET kinetics for the near bandgap excitation has not been reported. Herein, we investigate the IET kinetics of g-C3N4/Pt as a semiconductor/cocatalyst prototype by femtosecond time-resolved diffuse reflectance spectroscopy. We find that the near bandgap excitation of g-C3N4 inhibits the IET of g-C3N4/Pt due to electron deep trapping, resulting in a markedly decreased apparent quantum efficiency for photocatalytic H2 evolution. This work complements the kinetic understanding for the photocatalytic mechanism of the semiconductor/cocatalyst system in its whole light absorption range.