Hydroxyl-modified Nb₄C₃T_x MXene@ZnIn₂S₄ sandwich structure for photocatalytic overall water splitting

Herein, a hydroxyl-modified MXene@ZnIn₂S₄ (Nb₄C₃T_x MXene@ZIS-OH) overall water splitting photocatalyst with a sandwich structure was prepared through an in-situ growth strategy and peroxyl plasma post-treatment. The Nb₄C₃T_x MXene@ZIS-OH exhibits outstanding catalytic performance, which generates the release rates of hydrogen (53.8 μmol g^-1h^-1) and oxygen (26.7 μmol g^-1h^-1) from the water under visible light irradiation. After four photocatalytic cycling, the photocatalytic overall water splitting activity of Nb₄C₃T_x MXene@ZIS-OH is still 95.9% of the initial activity, which indicates that Nb₄C₃T_x MXene@ZIS-OH exhibits excellent cycling stability. Notably, the Nb₄C₃T_x MXene@ZIS-OH achieves an AQY of 1.2% for the overall photocatalytic water splitting at 380 nm. The sandwich structure and matched heterointerface between high work function Nb₄C₃T_x MXene and ZnIn₂S₄ nanosheets promote the electron transport, inhibit the charge recombination, and separate the generated H₂ and O₂ with effectiveness. Importantly, the Finite-Difference Time-Domain (FDTD) simulation suggests the hydroxyl groups on the surface of ZnIn₂S₄ could increase the hydrophilicity of photocatalyst and capture the holes generated by photoexcitation, thereby promoting the separation of electron-hole pairs rapidly. This work presents a successful example of constructing overall water splitting photocatalysts by energy level regulation, structure design and functional group modification.