Correlating flat band and onset potentials for solar water splitting on model hematite photoanodes
Journal article, 2015

Hematite (α-Fe2O3) is a very promising material for solar water splitting that requires a high anodic potential to initiate the oxygen evolution reaction (OER). In this work, we explore the correlation between the downshift in flat band potential of hematite, Vfb, and in onset potential of OER, Vonset, caused by prolonged annealing. We observed a cathodic shift (i.e., towards lower potentials) of 200 mV of Vonset on model photoanodes consisting of ultra-thin hematite films, upon increasing the oxidation time during fabrication and without any further modifications. Detailed physical characterization, electrochemical impedance spectroscopy, and Mott-Schottky analysis revealed a quantitative correlation between the cathodic shift of Vonset and a lowering of Vfb. We identified a reduction in concentration of grain boundaries with increasing oxidation time, as the mechanism behind the observed shift of the Vfb. The approach presented here can be seen as a complementary strategy to co-catalysts and other post-fabrication treatments to lower Vonset. Moreover, it is generically applicable to photoelectrodes used to carry out oxidation and reduction half-cell reactions.

Author

Beniamino Iandolo

Chalmers, Applied Physics, Chemical Physics

H. Zhang

University of New South Wales (UNSW)

Björn Wickman

Chalmers, Applied Physics, Chemical Physics

Igor Zoric

Chalmers, Applied Physics, Chemical Physics

G. Conibeer

University of New South Wales (UNSW)

Anders Hellman

Chalmers, Applied Physics, Chemical Physics

Competence Centre for Catalysis (KCK)

RSC Advances

2046-2069 (ISSN)

Vol. 5 75 61021-61030

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Energy

Materials Science

Subject Categories

Physical Chemistry

DOI

10.1039/c5ra10215d

More information

Created

10/7/2017