Effect of electron transfer on the photocatalytic hydrogen evolution efficiency of faceted TiO2/CdSe QDs under visible light

Abstract

Quantum dot (QD)/TiO₂ composites are widely used materials in the field of photocatalysis. However, the influence of different exposed facets of TiO₂ in composites on photocatalytic hydrogen evolution is rarely reported. In this work, CdSe QD–TiO₂ composites with dominant {001} or {101} faceted anatase were synthesized and specifically characterized using X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Photocatalytic hydrogen evolution tests reveal that {001}-TiO₂/CdSe QDs exhibit a 213.1- and 9.0-fold increase in photocatalytic activity compared to {001}-TiO₂ and CdSe QDs, respectively. Notably, the photocatalytic activity of {001}-TiO₂/CdSe QDs is 2.2 times higher than that of {101}-TiO₂/CdSe QDs. Based on the results from UV-Vis diffuse reflectance spectroscopy, Brunauer–Emmett–Teller surface area testing, Mott–Schottky testing and steady-state and time-resolved emission spectroscopy, the main reason for enhanced photocatalytic activity is the faster electron transfer from CdSe QDs to {001}-TiO₂ compared with to {101}-TiO₂. This research on tailored facets in QD/TiO₂ composites provides primary insights for the design of effective photocatalysts.