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Evidence and Effect of Photogenerated Charge Transfer for Enhanced Photocatalysis in WO 3 /TiO 2 Heterojunction Films: A Computational and Experimental Study

DOI: 10.1002/adfm.201605413 DOI Help

Authors: Carlos Sotelo-vazquez (University College London) , Raul Quesada-cabrera (University College London) , Min Ling (University College London, London) , David O. Scanlon (University College London; Diamond Light Source) , Andreas Kafizas (University College London) , Pardeep Kumar Thakur (Diamond Light Source) , Tien-lin Lee (Diamond Light Source) , Alaric Taylor (University College London) , Graeme W. Watson (Trinity College Dublin) , Robert G. Palgrave (University College London) , James R. Durrant (Imperial College London) , Christopher S. Blackman (University College London) , Ivan P. Parkin (University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Functional Materials , VOL 4

State: Published (Approved)
Published: March 2017

Abstract: Semiconductor heterojunctions are used in a wide range of applications including catalysis, sensors, and solar-to-chemical energy conversion devices. These materials can spatially separate photogenerated charge across the heterojunction boundary, inhibiting recombination processes and synergistically enhancing their performance beyond the individual components. In this work, the WO3/TiO2 heterojunction grown by chemical vapor deposition is investigated. This consists of a highly nanostructured WO3 layer of vertically aligned nanorods that is then coated with a conformal layer of TiO2. This heterojunction shows an unusual electron transfer process, where photogenerated electrons move from the WO3 layer into TiO2. State-of-the-art hybrid density functional theory and hard X-ray photoelectron spectroscopy are used to elucidate the electronic interaction at the WO3/TiO2 interface. Transient absorption spectroscopy shows that recombination is substantially reduced, extending both the lifetime and population of photogenerated charges into timescales relevant to most photocatalytic processes. This increases the photocatalytic efficiency of the material, which is among the highest ever reported for a thin film. In allying computational and experimental methods, this is believed to be an ideal strategy for determining the band alignment in metal oxide heterojunction systems.

Journal Keywords: band alignment; density functional theory; hard X-ray photoelectron spectroscopy; heterojunction; photocatalysis; transient absorption; titanium dioxide

Subject Areas: Materials, Chemistry

Instruments: I09-Surface and Interface Structural Analysis