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Type-II heterostructures of α -V 2 O 5 nanowires interfaced with cadmium chalcogenide quantum dots: Programmable energetic offsets, ultrafast charge transfer, and photocatalytic hydrogen evolution

DOI: 10.1063/1.5128148 DOI Help

Authors: Saurabh Chauhan (University at Buffalo, The State University of New York) , Aaron Sheng (University at Buffalo, The State University of New York) , Junsang Cho (Texas A&M University;) , Sara Abdel Razek (Binghamton University) , Nuwanthi Suwandaratne (University at Buffalo, The State University of New York) , Matthew Y. Sfeir (Brookhaven National Laboratory) , Louis F. J. Piper (Binghamton University) , Sarbajit Banerjee (Texas A&M University) , David F. Watson (University at Buffalo, The State University of New York)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: The Journal Of Chemical Physics , VOL 151

State: Published (Approved)
Published: December 2019
Diamond Proposal Number(s): 22148

Abstract: 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.

Journal Keywords: Electron transfer; Semiconductors; Charge recombination; Electronic bandstructure; Quantum dots; Nanowires; Density functional theory; Heterostructures; X-ray photoelectron spectroscopy; Photocatalysis

Subject Areas: Chemistry, Physics, Energy

Instruments: I09-Surface and Interface Structural Analysis

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