Near-complete suppression of surface losses and total internal quantum efficiency in BiVO4photoanodes

Bismuth vanadate (BiVO 4 ) is one of the most efficient light absorbing metal oxides for solar water splitting. BiVO 4 photoanodes immersed in an electrolyte in an open circuit configuration and exposed to simulated solar illumination for prolonged time achieve superior photoelectrochemical (PEC) activity. This photocharging (PC) effect is capable of almost completely overcoming the surface and bulk limitations of BiVO 4 . Herein we show that alkaline conditions favor the PC effect; specifically BiVO 4 photoanodes subjected to PC treatment at pH 10 achieve a record high photocurrent for undoped and uncatalyzed BiVO 4 of 4.3 mA cm 2 @ 1.23 V RHE , an outstandingly low onset potential of 0.25 V RHE , and a very steep photocurrent onset. Alkaline conditions also facilitate excellent external and internal quantum efficiencies of 75 and 95% respectively (average in the 440 nm 4 l 4 330 nm range). Moreover, Received 19th December 2016, Accepted 26th May 2017 impedance spectroscopy and in situ XAS study suggest that electronic, structural and chemical properties of the bulk of these films remain unchanged during the PC treatment. However, appreciable DOI: 10.1039/c6ee03677e changes in the surface-related properties take place. Ultimately, our results indicate that the improved activity of PC-BiVO 4 is enhanced by surface reaction pathways of the semiconductor-liquid junction, rsc.li/ees which is directly correlated with the electrochemical environment in which it is modified.