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Published July 25, 2013 | Supplemental Material
Journal Article Open

Comparison between the Quantum Yields of Compact and Porous WO_3 Photoanodes

Abstract

Ordered structures offer the potential for producing photoanodes with enhanced minority-carrier collection. To evaluate this approach to visible-light-driven oxidation in aqueous electrolytes, porous WO_3 structures were synthesized by the potentiostatic anodization of W foil. The photoelectrochemical behavior of the porous WO_3 photoanodes was compared to that of compact WO_3 films. Relative to planar electrodes, the porous WO_3 electrodes exhibited a 6-fold increase in photocurrent density, from 0.12 to 0.75 mA cm^(–2), under 100 mW cm^(–2) of simulated solar illumination. Spectral response measurements indicated that the porous electrodes exhibited internal quantum yields of 0.5 throughout most of the region of WO_3 absorption. The external quantum yield of the porous WO_3 films was a function of the angle of incidence of the light, increasing from 0.25 at normal incidence to 0.50 at 65° off normal. The porous WO_3 films showed excellent stability against photodegradation. This work demonstrates that morphological control can improve the internal quantum yield of photoanodes in contact with aqueous electrolytes.

Additional Information

© 2013 American Chemical Society. Received: March 13, 2013; Revised: June 15, 2013; Published: June 17, 2013. This work was funded by the NSF Powering the Planet Center for Chemical Innovation, grant CHE-0947829, and by the Defense Advanced Research Projects Agency. Use of facilities at the Molecular Materials Research Center (MMRC) at Caltech is gratefully acknowledged. The authors also acknowledge the technical work of Miguel Ortiz from California State University, Los Angeles.

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