Z-Scheme Charge Flow Activates ZnCo2S4 as an Electron-Aggregation Site for Photocatalytic Hydrogen Evolution

Hydrogen energy, as a new, clean and renewable energy, has great potential to address the global energy crisis and environmental pollution. This study presents a ZnCo 2 S 4 /ZnIn 2 S 4 (ZCS/ZIS) heterojunction photocatalyst, where the charge transfer mechanism ingeniously transforms the role of ZnCo 2 S 4 . While individually photocatalytically inactive, ZnCo 2 S 4 becomes crucial in the ZCS/ZIS composite. Driven by a built-in electric field arising from their difference in Fermi level, a direct Z-scheme charge flow is established. This flow not only facilitates the separation of photogenerated electrons and holes at the interface but also, more importantly, activates ZnCo 2 S 4 as a primary electron aggregation site. Consequently, strongly reductive electrons are efficiently enriched on ZnCo 2 S 4 for the hydrogen evolution reaction. The optimized ZCS/ZIS composite achieves an exceptional H 2 production rate of 6.60 mmol g −1 h −1 under visible light, which is 9.3 times that of ZnIn 2 S 4 , with an apparent quantum yield of 7.96% at 400 nm. This work highlights the strategic design of charge dynamics to unlock the latent functionality of components within a Z-scheme system. Graphical This work constructs a ZnCo 2 S 4 /ZnIn 2 S 4 Z-scheme heterojunction, where the charge flow ingeniously transforms inactive ZnCo 2 S 4 into a crucial electron-aggregation site. This strategic design simultaneously achieves efficient charge separation and preserves high redox potential, leading to a dramatically enhanced photocatalytic H 2 evolution rate under visible light.