Rational design of a 2D TiO2–MoO3 step-scheme heterostructure for boosted photocatalytic overall water splitting

Abstract

The design of step-scheme (S-scheme) heterostructure photocatalysts is a promising strategy for the high utilization of photogenerated charge carriers. Herein, a novel S-scheme two-dimensional (2D) TiO₂–MoO₃ heterojunction photocatalyst is fabricated by a facile electrochemical method for high water splitting photocatalytic efficiency. According to X-ray photoelectron spectroscopy (XPS) assessment, electrons are transported from TiO₂ to MoO₃ upon close contact, creating an internal electric field (IEF) directed from TiO₂ to MoO₃. Hence, upon light irradiation, the photogenerated electrons in MoO₃ move toward TiO₂ under the IEF effect, as revealed by EPR analysis, implying that the S-scheme heterojunction was established in the TiO₂–MoO₃ heterostructure and significantly promoted the separation of electron–hole pairs to enhance efficient photocatalytic water splitting. Thanks to the 2D morphology of the TiO₂–MoO₃ heterojunction and the significantly improved redox capability of the charge carriers in the S-scheme system, the photocatalytic water splitting efficiency of the optimized TiO₂–MoO₃ is higher than those of both pure MoO₃ and TiO₂ and commercial TiO₂–P25. This study, for the first time, presents the charge transfer pathways in the TiO₂–MoO₃ heterostructure photocatalyst via an S-scheme system. It will shed new light on the design and fabrication of novel step-scheme heterojunction photocatalysts for overall water splitting.