All‐Solid‐State S‐Scheme Heterojunction TiO2/Cu/MoSi2N4 for Efficient Visible‐Light Driven Water Splitting

Abstract In the fields of new energy and environmental protection, the development of highly efficient, low‐cost, eco‐friendly, and stable photoelectrocatalysts has drawn significant interest. Inspired by the high redox potential of S‐scheme heterojunctions and the structural advantage of all‐solid‐state Z‐scheme junctions, a novel all‐solid‐state S‐scheme heterojunction TiO 2 /Cu/MoSi 2 N 4 nanorod (NR) array is designed and prepared using hydrothermal and magnetron sputtering methods. Under the synergistic effect of the built‐in electric field, high redox potential, and conductive Cu medium, light absorption is extended to the visible‐light region, and the separation and transfer efficiencies of the photogenerated carriers are significantly improved. As a result, under > 420 nm visible‐light irradiation, the photocurrent density is enhanced by 2.91 times to −18.24 mA cm −2 at −1.39 V versus reversible hydrogen electrode, and the surface photovoltage is also increased by 7.77 times. Furthermore, the photoelectrochemical (PEC) H 2 evolution rate of TiO 2 /Cu/MoSi 2 N 4 is improved to 1.76 µmol cm −2 h −1 and exhibits robust stability. The enhancement mechanism of the PEC performance is systematically explored by combining the experimental results with first‐principles calculations. The findings indicate that the construction of an all‐solid‐state S‐scheme heterojunction is a promising strategy to improve PEC performance and can be applied to other photoelectrocatalysts.