Improved current collection in WO 3 :Mo/WO 3 bilayer photoelectrodes
- PDF / 1,225,459 Bytes
- 7 Pages / 584.957 x 782.986 pts Page_size
- 14 Downloads / 193 Views
Bjorn Marsen Solar Energy Research, Helmholtz-Zentrum Berlin fu¨r Materialien und Energie, Lise-Meitner-Campus, D-14109 Berlin, Germany
Lothar Weinhardt Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154-4003; and Experimentelle Physik II, Universita¨t Wu¨rzburg, D-97074 Wu¨rzburg, Germany
Marcus Ba¨r Solar Energy Research, Helmholtz-Zentrum Berlin fu¨r Materialien und Energie, Lise-Meitner-Campus, D-14109 Berlin, Germany; and Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154-4003
Clemens Heske Department of Chemistry, University of Nevada, Las Vegas, Nevada 89154-4003
Kwang-Soon Ahn, Yanfa Yan, and Mowafak M. Al-Jassim National Renewable Energy Laboratory, Golden, Colorado 80401 (Received 9 June 2009; accepted 30 June 2009)
We report on the incorporation of molybdenum into tungsten oxide by co-sputtering and its effect on solar-powered photoelectrochemical (PEC) water splitting. Our study shows that Mo incorporation in the bulk of the film (WO3:Mo) results in poor PEC performance when compared with pure WO3, most likely due to defects that trap photo-generated charge carriers. However, when a WO3:Mo/WO3 bilayer electrode is used, a 20% increase of the photocurrent density at 1.6 V versus saturated calomel reference electrode is observed compared with pure WO3. Morphological and microstructural analysis of the WO3:Mo/WO3 bilayer structure reveals that it is formed by coherent growth of the WO3:Mo top layer on the WO3 bottom layer. This effect allows an optimization of the electronic surface structure of the electrode while maintaining good crystallographic properties in the bulk.
I. INTRODUCTION
Tungsten oxide semiconductor materials have been largely studied for electrochromic,1–3 gas sensing,4–6 and water-splitting7–10 applications. Good electron transport properties and sufficient stability against corrosion recommend WO3 as a candidate material for photoelectrochemical (PEC) hydrogen production. Furthermore, compared with the optical properties of another prominent PEC candidate material, TiO2,11 WO3 (with an optical band gap “EG” of approximately 2.6 eV12) makes better use of the solar spectrum. However, from an industrial hydrogen a)
Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http:// www.mrs.org/jmr_policy DOI: 10.1557/JMR.2010.0019 J. Mater. Res., Vol. 25, No. 1, Jan 2010
http://journals.cambridge.org
Downloaded: 11 Mar 2015
production perspective, high evolution rates will not be achieved with pure WO3 materials because this band gap value is still too large (note that a band gap value at approximately 2.0 eV is considered to be ideal for PEC applications13,14). At the Hawaii Natural Energy Institute (HNEI), several experiments have been conducted to reduce the band gap of reactively sputtered WO3 films by incorporating impurities in the material b
Data Loading...
