A Bismuth Vanadate–Cuprous Oxide Tandem Cell for Overall Solar Water Splitting

• Published in: Journal of physical chemistry. C Vol. 118; no. 30; pp. 16959 - 16966
• Main Authors: Bornoz, Pauline, Abdi, Fatwa F, Tilley, S. David, Dam, Bernard, van de Krol, Roel, Graetzel, Michael, Sivula, Kevin
• Format: Journal Article
• Language: English
• Published: American Chemical Society 31.07.2014
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp500441h

Through examination of the optoelectronic and photoelectrochemical properties of BiVO4 and Cu2O photoelectrodes, we evaluate the feasibility of a BiVO4/Cu2O photoanode/photocathode tandem cell for overall unassisted solar water splitting. Using state-of-the-art photoelectrodes we identify current-matching conditions by altering the photoanode active layer thickness. By further employing water oxidation and reduction catalysts (Co-Pi and RuO x , respectively) together with an operating point analysis, we show that an unassisted solar photocurrent density on the order of 1 mA cm–2 is possible in a tandem cell and moreover gain insight into routes for improvement. Finally, we demonstrate the unassisted 2-electrode operation of the tandem cell. Photocurrents corresponding to ca. 0.5% solar-to-hydrogen conversion efficiency were found to decay over the course of minutes because of the detachment of the Co-Pi catalyst. This aspect provides a fundamental challenge to the stable operation of the tandem cell with the currently employed catalysts.