Tracking S-Scheme Charge Transfer Pathways in Mo₂C/CdS H₂-Evolution Photocatalysts

Developing efficient and low-cost photocatalysts and deep investigations on the charge separation and transfer pathways are still two key challenges in achieving practical photocatalytic application. Herein, the NiS-modified Mo₂C/CdS layered nanojunction with cascade 2D coupling interfaces for efficient photocatalytic H₂ evolution is constructed. The as-prepared ternary step-scheme (S-scheme) photocatalysts show excellent photocatalytic hydrogen-evolution performance of 24.03 mmol g⁻¹ h⁻¹, which is 7.83 and 3.83 times higher than that of CdS and CdS/NiS. Surprisingly, it is found that Mo₂C can serve as a semiconductor in photocatalytic hydrogen evolution, instead of as a cocatalyst. The charge transfer pathways from Mo₂C to CdS are identified via both, in situ irradiation X-ray photoelectron spectroscopy (XPS) (ISI XPS) and ultraviolet photoelectron spectroscopy (UPS). Notably, this is the first report using Mo₂C as a semiconductor for photocatalytic application, which gives full play to the advantages of light-harvesting and charges separation.