All‐Solid‐State S‐Scheme Heterojunction TiO 2 /Cu/MoSi 2 N 4 for Efficient Visible‐Light Driven Water Splitting

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 TiO₂/Cu/MoSi₂N₄ 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) H₂ evolution rate of TiO₂/Cu/MoSi₂N₄ 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.