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Photoactivity and Stability of WO3/BiVO4 Photoanodes: Effects of the Contact Electrolyte and of Ni/Fe Oxyhydroxide Protection C

Grigioni, Ivan, Corti, Annamaria, Dozzi, Maria Vittoria, Selli, Elena
Journal of physical chemistry 2018 v.122 no.25 pp. 13969-13978
catalysts, electric current, electrodes, electrolytes, iron, iron oxyhydroxides, nickel, oxidation, oxygen production, pH, physical chemistry, potassium phosphates, semiconductors, sodium sulfate
Photoelectrodes with the WO₃/BiVO₄ heterojunction architecture are among the most efficient semiconductor oxide-based photoanodes for water oxidation. However, because of the different experimental conditions employed in their photoelectrochemical characterization (in particular the nature and concentration of the contact electrolyte and the pH of the solution), a direct and unambiguous comparison of their performance obtained in different laboratories is often quite difficult. In this work, we systematically tested identical WO₃/BiVO₄ photoanodes in contact with solutions of the most commonly used electrolytes, i.e. Na₂SO₄ and the potassium phosphate buffer (KPi), at various electrolyte concentration and pH. Furthermore, WO₃/BiVO₄ photoanodes protected with a Ni/Fe oxyhydroxide oxygen evolution catalyst were also tested under identical conditions. In contact with KPi solutions, both unprotected and protected electrodes produce higher photocurrent than in contact with Na₂SO₄ solutions, but they proved to be less stable, particularly under basic conditions. WO₃/BiVO₄ heterojunction systems modified by deposition of the Ni/Fe oxyhydroxide cocatayst proved to be more stable and to produce higher photocurrent, with a cathodic shift of the photocurrent onset.