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 photo electrochemical (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.