Z-scheme heterojunction photocatalyst: Deep eutectic solvents-assisted synthesis of Cu2O nanocluster improved hydrogen production of TiO2

The development of nanocluster scale heterojunction catalysts using a green method for solar energy conversion applications is an important challenge. In this study, deep eutectic solvents (DESs)-assisted process was employed as a green approach to synthesize size-controlled Cu2O nanoclusters on TiO2 surfaces without using any size-controlling agent. The Cu2O nanoclusters (1.5 nm) interact with the subdomain surface of TiO2 nanoparticles, forming Z-scheme heterojunction, resulting in the effective separation of photogenerated charge carriers. Also, the surface chemical environment of the Cu2O/TiO2 composite was altered by the formation of defects during the in-situ Cu2O synthesis, which generated oxygen vacancies. The optimized Cu2O/TiO2 catalyst has a high charge density (16.3 ×1019 cm−3) and 2.38 times less charge transfer resistance compared to pristine TiO2. The optimized Cu2O/TiO2 photocatalysts had a 1.32 times higher H2 production rate (24.21 mmol g−1 h−1) than pristine TiO2. This study provides new insight into the development of monosized Cu2O nanoclusters on TiO2 by DESs assisted process as a green synthesis approach for photocatalytic hydrogen production. [Display omitted] •A Deep eutectic solvent-assisted process was developed for the synthesis of monosized Cu2O nanocluster on TiO2 nanoparticles.•The interface between monosized Cu2O and the subdomain surface of TiO2 improves the charge transfer dynamic.•Defects-induced surface follows the Z-scheme type charge carriers’ migration for effective separation.•Heterojunction increases surface charge density, enhancing the hydrogen production rate of Cu2O/TiO2 nanocomposite.