Construction of Dual S-Scheme Heterojunction Based Co₉S₈ QDs Coupling with NiS/CdS Concave Cubic Derived from Prussian Blue Analog for Enhanced Photocatalytic Hydrogen Evolution

The design and development of high-efficiency and low-energy consumption catalysts for hydrogen evolution are critical to mitigating environmental problems. Herein, amorphous Co9S8 quantum dots (QDs) are prepared by hydrothermal method and loaded on concave cubic NiS/CdS derived from Prussian blue analog (PBA) to construct an efficient Co9S8 QDs/NiS/CdS dual S-scheme heterojunction photocatalysts, showing excellent photocatalytic hydrogen performance of 13.45 mmolg(-1)h(-1), which is 5.42 times higher than that of pure CdS. The improved photocatalytic performance is ascribed to the creation of a double S-scheme heterojunction, quantum confinement effect, and a concave cubic structure, accelerating electron transport and offering ample surface active sites. The possible mechanism is demonstrated with valence band XPS (VB-XPS), ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT) calculations. This work provides insight into the exploration of PBA-based photocatalysts to improve photocatalytic hydrogen evolution and provides an effective strategy for the design of photocatalysts with double the S-scheme heterojunction.