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Correlating flat band and onset potentials for solar water splitting on model hematite photoanodes

Beniamino Iandolo (Institutionen för teknisk fysik, Kemisk fysik) ; H. Zhang ; Björn Wickman (Institutionen för teknisk fysik, Kemisk fysik) ; Igor Zoric (Institutionen för teknisk fysik, Kemisk fysik) ; G. Conibeer ; Anders Hellman (Institutionen för teknisk fysik, Kemisk fysik ; Kompetenscentrum katalys (KCK))
RSC Advances (2046-2069). Vol. 5 (2015), 75, p. 61021-61030.
[Artikel, refereegranskad vetenskaplig]

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.

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Denna post skapades 2015-08-24. Senast ändrad 2015-12-01.
CPL Pubid: 221096


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Institutioner (Chalmers)

Institutionen för teknisk fysik, Kemisk fysik (1900-2015)
Kompetenscentrum katalys (KCK)


Nanovetenskap och nanoteknik
Fysikalisk kemi

Chalmers infrastruktur