Correlating flat band and onset potentials for solar water splitting on model hematite photoanodes
Artikel i vetenskaplig tidskrift, 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.

Författare

Beniamino Iandolo

Chalmers, Teknisk fysik, Kemisk fysik

H. Zhang

University of New South Wales (UNSW) Australia

Björn Wickman

Chalmers, Teknisk fysik, Kemisk fysik

Igor Zoric

Chalmers, Teknisk fysik, Kemisk fysik

G. Conibeer

University of New South Wales (UNSW) Australia

Anders Hellman

Chalmers, Teknisk fysik, Kemisk fysik

Kompetenscentrum katalys (KCK)

RSC Advances

2046-2069 (ISSN)

Vol. 5 61021-61030

Styrkeområden

Nanovetenskap och nanoteknik

Energi

Materialvetenskap

Ämneskategorier

Fysikalisk kemi

DOI

10.1039/c5ra10215d