Enhanced photocatalytic H2 evolution based on a Ti3C2/Zn0.7Cd0.3S/Fe2O3 Ohmic/S-scheme hybrid heterojunction with cascade 2D coupling interfaces

Herein, the metallic Ti3C2 nanosheets decorated 2D-2D Zn0.7Cd0.3S (ZCS)-Fe2O3 Ohmic/step-scheme (S-scheme) hybrid heterojunction with cascade 2D coupling interfaces was rationally synthesized by oil bath and hydrothermal methods. The construction of both S-scheme and Ohmic heterojunctions was identified via in-situ irradiation XPS (ISI XPS), Electron spin resonance (ESR) or ultraviolet photoelectron spectroscopy (UPS) experiments, which can greatly improve the photocatalytic H2 evolution raction (HER) rate and stability. The H2 evolution rates of ZCS/0.5 Ti3C2, ZCS/2 Fe2O3 and ZCS/0.5 Ti3C2/2 Fe2O3 were 1.91, 2.0 and 6.35 times higher than that of pure ZCS nanosheets (NSs), respectively. The optimized ternary composite exhibits a highest HER activity of 27.24 mmol g−1h−1, with an apparent quantum efficiency of 20.92% at 450 nm. Meanwhile, the ternary photocatalyst still exhibited much higher stability. Clearly, the strong S-scheme interfacial electric fields could effectively promote spatial charge separation between ZCS nanosheets and Fe2O3 nanosheets, while 2D Ti3C2 MXene nanosheets, as an Ohmic-junction H2-evolution co-catalyst, could provide more electron transfer pathways and a large number of active sites for photocatalytic HER. It is expected that this work can offer some new idea or inspirations to rationally design highly efficient S-scheme heterojunction photocatalysts for further practical applications.