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On the influence of acceptor and donor doping on the protonic surface conduction of TiO2

Abstract

The transport of protonic charge carriers along and within the pore surfaces of porous oxide matrices is of significant importance for many catalytic and electrochemical applications, with porous TiO2 being a candidate material for both photo-catalytic applications and as an electronically conducting support for polymer-based electrochemical cells. This work investigates the effect of acceptor (Cr, Fe) and donor doping (Nb) on surface protonic conduction in porous TiO2 over a wide range of relative humidity, temperature and oxygen activity. Generally, we find that acceptor dopants on the surface counteract dissociation and reduces the mobility of protons, while donors give rise to enhanced dissociation making the surface protonic conduction highest for the donor-doped samples, contrary to conventional bulk proton conductors. Moreover, protonic surface conduction in Cr-doped TiO2 is significantly higher under oxidising compared to reducing conditions, which we relate to presence of higher valent species such as Cr6+ on the surface under oxidising conditions, again emphasising that protonic surface conduction increases with higher-valent (donor) and more acidic cations present on the surface.

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Publication details

The article was received on 25 Jan 2018, accepted on 11 May 2018 and first published on 14 May 2018


Article type: Paper
DOI: 10.1039/C8CP00571K
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    On the influence of acceptor and donor doping on the protonic surface conduction of TiO2

    S. Ø. Ø. Stub, K. Thorshaug, P. M. Rørvik, T. Norby and E. Vøllestad, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP00571K

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