Photoelectrochemical cell for unassisted overall solar water splitting using a BiVO4 photoanode and Si nanoarray photocathode
Overall solar water splitting without external bias was demonstrated in this study using a photoelectrochemical tandem device composed of a BiVO4 photoanode and Si nanoarray photocathode. An unassisted photocurrent density of 0.6 mA cm−2 is possible under AM 1.5G illumination, by examining the current density–voltage curves of respective photoelectrodes and the operating point in the three-electrode system. We then investigated the unassisted two-electrode operation of the tandem cell, and a solar-to-hydrogen efficiency of 0.57% (corresponding photocurrent density of 0.46 mA cm−2) was achieved under AM 1.5G illumination (100 mW cm−2). The solar photocurrent density of this tandem cell decayed during the stability testing, possibly due to the dissolution of the Co-Pi electrocatalyst rather than the instability of the p-Si photocathode.