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Surface State Trapping and Mobility Revealed by Junction Electrochemistry of Nano-Cr2O3

Cummings, Charles Y., Attard, Gary Anthony, Mitchels, John M. and Marken, Frank 2012. Surface State Trapping and Mobility Revealed by Junction Electrochemistry of Nano-Cr2O3. Australian Journal of Chemistry 65 (1) , pp. 65-71. 10.1071/CH11382

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Abstract

Hydrous chromium oxide nanoparticles (~15 nm diameter) are assembled from a colloidal solution onto tin-doped indium oxide (ITO) substrates by layer-by-layer electrostatic deposition with aqueous carboxymethyl-cellulose sodium salt binder. Calcination produces purely inorganic mesoporous films (average thickness increase per layer of 1 nm) of chromia Cr2O3. When immersed in aqueous carbonate buffer at pH 10 and investigated by cyclic voltammetry, a chemically reversible oxidation is observed because of a conductive layer at the chromia surface (formed during initial potential cycling). This is attributed to a surface CrIII/IV process. At more positive potentials higher oxidation states are accessible before film dissolution. The effects of film thickness and pH on voltammetric responses are studied. X-Ray photoelectron spectroscopy (XPS) evidence for higher chromium oxidation states is obtained. ITO junction experiments are employed to reveal surface conduction by CrIII/IV and CrIV/V ‘mobile surface states’ and an estimate is obtained for the apparent CrIII/IV charge surface diffusion coefficient Dapp = 10–13 m2 s–1. The junction experiment distinguishes mobile surface redox sites from energetically distinct deeper-sitting ‘trapped states’.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Subjects: Q Science > QD Chemistry
Publisher: CSIRO Publishing
ISSN: 0004-9425
Funders: EPSRC
Last Modified: 04 Jun 2017 03:18
URI: http://orca.cf.ac.uk/id/eprint/19596

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