Issue 7, 2015

Oxygen deficient α-Fe2O3 photoelectrodes: a balance between enhanced electrical properties and trap-mediated losses

Abstract

Intrinsic doping of hematite through the inclusion of oxygen vacancies (VO) is being increasingly explored as a simple, low temperature route to preparing active water splitting α-Fe2O3−x photoelectrodes. Whilst it is widely accepted that the introduction of VO leads to improved conductivities, little else is verified regarding the actual mechanism of enhancement. Here we employ transient absorption (TA) spectroscopy to build a comprehensive kinetic model for water oxidation on α-Fe2O3−x. In contrast to previous suggestions, the primary effect of introducing VO is to block very slow (ms) surface hole – bulk electron recombination pathways. In light of our mechanistic research we are also able to identify and address a cause of the high photocurrent onset potential, a common issue with this class of electrodes. Atomic layer deposition (ALD) of Al2O3 is found to be particularly effective with α-Fe2O3−x, leading to the photocurrent onset potential shifting by ca. 200 mV. Significantly TA measurements on these ALD passivated electrodes also provide important insights into the role of passivating layers, that are relevant to the wider development of α-Fe2O3 photoelectrodes.

Graphical abstract: Oxygen deficient α-Fe2O3 photoelectrodes: a balance between enhanced electrical properties and trap-mediated losses

Supplementary files

Article information

Article type
Edge Article
Submitted
04 févr. 2015
Accepted
28 avr. 2015
First published
28 avr. 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2015,6, 4009-4016

Oxygen deficient α-Fe2O3 photoelectrodes: a balance between enhanced electrical properties and trap-mediated losses

M. Forster, R. J. Potter, Y. Ling, Y. Yang, D. R. Klug, Y. Li and A. J. Cowan, Chem. Sci., 2015, 6, 4009 DOI: 10.1039/C5SC00423C

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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