Type-II heterostructures of α-V₂O₅ nanowires interfaced with cadmium chalcogenide quantum dots: Programmable...

We synthesized a new class of heterostructures by depositing CdS, CdSe, or CdTe quantum dots (QDs) onto α-V₂O₅ nanowires (NWs) via either successive ionic layer adsorption and reaction (SILAR) or linker-assisted assembly (LAA). SILAR yielded the highest loadings of QDs per NW, whereas LAA enabled better control over the size and properties of QDs. Soft and hard x-ray photoelectron spectroscopy in conjunction with density functional theory calculations revealed that all α-V₂O₅/QD heterostructures exhibited Type-II band offset energetics, with a staggered gap where the conduction- and valence-band edges of α-V₂O₅ NWs lie at lower energies (relative to the vacuum level) than their QD counterparts. Transient absorption spectroscopy measurements revealed that the Type-II energetic offsets promoted the ultrafast (10^-12-10^-11 s) separation of photogenerated electrons and holes across the NW/QD interface to yield long-lived (10^-6 s) charge-separated states. Charge-transfer dynamics and charge-recombination time scales varied subtly with the composition of heterostructures and the nature of the NW/QD interface, with both charge separation and recombination occurring more rapidly within SILAR-derived heterostructures. LAA-derived α-V₂O₅/CdSe heterostructures promoted the photocatalytic reduction of aqueous protons to H₂ with a 20-fold or greater enhancement relative to isolated colloidal CdSe QDs or dispersed α-V₂O₅ NWs. The separation of photoexcited electrons and holes across the NW/QD interface could thus be exploited in redox photocatalysis. In light of their programmable compositions and properties and their Type-II energetics that drive ultrafast charge separation, the α-V₂O₅/QD heterostructures are a promising new class of photocatalyst architectures ripe for continued exploration.