Photocatalytic H2 production over S-scheme Co3Se4/TiO2 nanosheet with super-hydrophilic surface

Photocatalytic H2 evolution represents a sustainable technology to acquire green energy via a solar energy conversion process. The development of photocatalysts with simple preparation and superior activity is still highly desired. In this work, the H2 evolution activities of cobalt selenide (Co3Se4) microspheres decorated TiO2 were investigated for the first time. The 25 wt% Co3Se4/TiO2 hybrid delivers an optimum H2 production rate of 6065 μmol·g−1·h−1 in 20 vol% TEOA under 300 W Xe lamp irradiation, which is 12.5 and 13.4 times that of pristine TiO2 (484 μmol·g−1·h−1) and pure Co3Se4 (453 μmol·g−1·h−1), respectively. The enhanced activity benefits from the S–scheme heterojunction formed between Co3Se4 and TiO2, which can obviously promote the separation of charge carriers and reduce the overpotential of H2 generation. Besides, the surface composition of the sample after reaction was revealed through XRD, TEM, XPS and water contact angle measurements, the results show that the microstructure of the composite sample remains unchanged after reaction, and a thin oxide or hydroxide layer was in–situ formed on the surface of Co3Se4, leading to a super–hydrophilic surface of Co3Se4/TiO2 and endowing with long reaction stability. This work broadens the application of Co3Se4 in energy conversion and provides a promising option to replace traditional noble metal photocatalysts.