Chemical Stability of CuWO4 for Photoelectrochemical Water Oxidation

• Published in: Journal of physical chemistry. C Vol. 117; no. 17; pp. 8708 - 8718
• Main Authors: Yourey, Joseph E, Pyper, Kayla J, Kurtz, Joshua B, Bartlett, Bart M
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 02.05.2013
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic transport in condensed matter; Exact sciences and technology; Photoconduction and photovoltaic effects; photodielectric effects; Physics; pH value; Chemical stability; Photocurrents; pH effect; Precursor; Hydrogen 1; Casting; Potassium phosphate; Chlorides; Illumination; Oxidation; Photoconductivity; Charge transfer; Sol-gel process; Photoelectrode; Borates
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp402048b

Pure-phase CuWO4 photoanodes with 200 nm thickness were produced by spin-casting sol–gel precursors to evaluate their performance as photoelectrodes for water oxidation. The stability of CuWO4 in potassium phosphate (KPi) and potassium borate (KBi) buffers was evaluated as a function of pH and irradiance. CuWO4 photoanodes demonstrate higher stability at pH 3 and 5 in a 0.1 M KPi buffer and are significantly more stable over a 12 h period of illumination in a 0.1 M KBi buffer at pH 7 (∼75 μA/cm2 photocurrent at 1.23 V vs RHE (reversible hydrogen electrode) and 1 sun illumination) than in a 0.1 M KPi buffer at pH 7. The onset of photoelectrochemical water oxidation and electrochemical O2 reduction is dictated by Cu(3d x 2–y 2 ) states that reside at 0.4 V vs RHE, determined by linear sweep voltammetry. The onset for water oxidation is hindered by a large charge-transfer resistance, as high as 4.6 kΩ at 1 V vs RHE. Nevertheless, CuWO4 photoanodes show nearly quantitative faradic efficiency for water oxidation, even in the presence of chloride, an improvement over the binary oxide WO3.