Type-II heterostructures of -V2O5 nanowires interfaced with cadmium chalcogenide quantum dots: Programmable energetic offsets, ultrafast charge transfer, and photocatalytic hydrogen evolution.
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We synthesized a new class of heterostructures by depositing CdS, CdSe, or CdTe quantum dots (QDs) onto -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 -V2O5/QD heterostructures exhibited Type-II band offset energetics, with a staggered gap where the conduction- and valence-band edges of -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 -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 -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 -V2O5/QD heterostructures are a promising new class of photocatalyst architectures ripe for continued exploration.
Chauhan, S., Sheng, A., Cho, J., Razek, S. A., Suwandaratne, N., Sfeir, M. Y., ... Watson, D. F.
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Chauhan, Saurabh||Sheng, Aaron||Cho, Junsang||Razek, Sara Abdel||Suwandaratne, Nuwanthi||Sfeir, Matthew Y||Piper, Louis FJ||Banerjee, Sarbajit||Watson, David F
