Photothermal-Effect-Enhanced Photoelectrochemical Water Splitting in MXene-Nanosheet-Modified ZnO Nanorod Arrays

Engineering semiconductor photoelectrodes with excellent photogenerated charge separation and transportation capabilities is of great practical interest for efficient photoelectrochemical (PEC) water splitting. Herein, MXene nanosheets as a bifunctional surface modifier were grafted onto ZnO nanorod arrays for enhanced PEC water oxidation performance. As a hole transfer material, the MXene nanosheets combine with ZnO nanorods to construct a heterojunction for restraining the recombination of photogenerated charges and boosting charge separation. Furthermore, as a photothermal material, the MXene nanosheets can produce a lot of heat for elevating the surface temperature of photoanodes in situ under extra near-infrared (NIR) irradiation, thus accelerating the charge transfer and improving the oxygen evolution reaction kinetics. As a result, the photocurrent density, durability, bulk charge separation, and surface charge injection efficiency of the ZnO/MXene-NIR photoanode outperform significantly those of pure ZnO photoanodes. This proof-of-concept work may shed light on the development of advanced semiconductor-based composite materials with the synergy of the photoelectric and photothermal effects for solar energy conversion.