Makwana, NM; Quesada-Cabrera, R; Parkin, IP; McMillan, PF; Mills, A; Darr, JA; (2014) A simple and low-cost method for the preparation of self-supported TiO2-WO3 ceramic heterojunction wafers. Journal of Materials Chemistry A , 2 (41) pp. 17602-17608. 10.1039/c4ta03257h.

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Abstract

Robust, bilayer heterojunction photodiodes of TiO2–WO3 were prepared successfully by a simple, low-cost powder pressing technique followed by heat-treatment. Exclusive photoirradiation of the TiO2 side of the photodiode resulted in a rapid colour change (dark blue) on the WO3 surface as a result of reduction of W6+ to W5+ (confirmed by X-ray photoelectron spectroscopy). This colour was long lived and shown to be stable in a dry environment in air for several hours. A similar photoirradiation experiment in the presence of a mask showed that charge transfer across the heterojunction occurred approximately normal to the TiO2 surface, with little smearing out of the mask image. As a result of the highly efficient vectorial charge separation, the photodiodes showed a tremendous increase in photocatalytic activity for the degradation of stearic acid, compared to wafers of the respective individual materials when tested separately.

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