Modification of electron transfer paths in CdS-TiO2 Z-type heterojunction by cobalt-based complexes for boosting visible-light photocatalytic hydrogen evolution

Abstract

Ti-oxo clusters as photocatalytic heterojunction precursor materials are a promising strategy for preparing TiO2. Enhancing the utilization of photogenerated electrons and increasing the delivery channel of these electrons can improve the performance of photocatalytic materials for H2 evolution significantly. Hereby, a novel ternary [TiO2-CdS QDs-5/Co(bpy)3Cl2] photocatalyst for highly efficient photocatalytic HER was reported for the first time. In this paper, a TiO2-CdS QDs-5 binary Z-type heterojunction was identified, and the photocatalytic HER yield was further improved by [Co(bpy)3Cl2]. The above-mentioned ternary system is advantageous for separating and transferring photogenerated electron-hole pairs. The photocatalytic HER rate of this catalytic system was 4440.84 μmol·h−1·g−1, which was 7.1 times more than that of TiO2-CdS QDs-5. The results indicate that the system is capable of maintaining stability and enhancement of the photocatalytic HER under visible light irradiation. In this study, we investigated photogenerated electron transfer pathways to improve the photocatalytic HER of TiO2 and we also revealed the electron transfer mechanism of TiO2-CdS QDs-5 Z-typed heterojunction with [Co(bpy)3Cl2] through DFT calculation. More importantly, this study presents a novel Z-type heterojunction catalyst, which enhance the electron transport path and this work provides an effective design concept for the development of TiO2-based materials for efficient photocatalytic HER.