Near-complete suppression of surface losses and total internal quantum efficiency in BiVO₄ photoanodes

Near-complete suppression of surface losses and total internal quantum efficiency in BiVO₄ photoanodes

Trzesniewski, B.J. (TU Delft ChemE/Materials for Energy Conversion and Storage)
Digdaya, I.A. (TU Delft ChemE/Materials for Energy Conversion and Storage)
Nagaki, T. (Student TU Delft)
Ravishankar, Sandheep (Universitat Jaume I)
Herraiz-Cardona, Isaac (Universitat Jaume I)
Vermaas, D.A. (TU Delft ChemE/Transport Phenomena)
Longo, Alessandro (Nederlandse Organisatie voor Wetenschappelijk Onderzoek)
Gimenez, Sixto (Universitat Jaume I)
Smith, W.A. (TU Delft ChemE/Materials for Energy Conversion and Storage)

2017-06-01

Bismuth vanadate (BiVO₄) is one of the most efficient light absorbing metal oxides for solar water splitting. BiVO₄ 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 BiVO₄. Herein we show that alkaline conditions favor the PC effect; specifically BiVO₄ photoanodes subjected to PC treatment at pH 10 achieve a record high photocurrent for undoped and uncatalyzed BiVO₄ 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 > λ > 330 nm range). Moreover, 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 changes in the surface-related properties take place. Ultimately, our results indicate that the improved activity of PC-BiVO₄ is enhanced by surface reaction pathways of the semiconductor-liquid junction, which is directly correlated with the electrochemical environment in which it is modified.

http://resolver.tudelft.nl/uuid:27ae71c2-b874-4327-ad4d-250dedd02394

https://doi.org/10.1039/c6ee03677e

1754-5692

Energy & Environmental Science, 10 (6), 1517-1529

Institutional Repository

journal article

© 2017 B.J. Trzesniewski, I.A. Digdaya, T. Nagaki, Sandheep Ravishankar, Isaac Herraiz-Cardona, D.A. Vermaas, Alessandro Longo, Sixto Gimenez, W.A. Smith