Photocatalytic hydrogen evolution mechanisms mediated by stereoactive lone pairs of Sb₂VO₅ in quantum dot heterostructures

Photocatalytic water splitting is a promising approach to generate clean hydrogen fuel and reduce climate change. Emulating Nature, semiconductor heterostructures with optimally aligned electronic states represent a promising design strategy. We report a tunable photocatalytic architecture by interfacing chalcogenide quantum dots (QDs) with Sb₂VO₅, a metal oxide semiconductor with a high density of optimally positioned lone-pair-derived mid-gap states, which enables barrier-less hole extraction from photoexcited CdS QDs. Comprehensive photoelectrochemical analyses show that the photoinduced charge carriers can catalyze reduction or oxidation half-reactions depending on the electrolyte composition, reactor environment, and the presence of co-catalysts. Ligand-bridged Sb₂VO₅-cysteine-CdS heterostructures photocatalytically generate H₂ without the need for an applied potential, external circuit, or counter electrode. The results provide a remarkable demonstration of the design of photocatalytic heterostructures based on electronic structure considerations to reduce energetic offsets and improve interfacial charge transfer to efficiently generate carbon-free H₂.