Quantitative investigation of CeO2 surface proton conduction in H2 atmosphere†
Abstract
This report is the first describing a study quantitatively analysing aspects of oxide surface protonics in a dry H2 atmosphere. Elucidating surface protonics is important for electrochemical and catalytic applications. In this study, AC impedance spectroscopy was used to investigate surface conduction properties of porous CeO2 at low temperatures (423–573 K) and in a dry H2 atmosphere. Results demonstrated that the conductivity increased by several orders of magnitude when H2 was supplied. Dissociative adsorption of H2 contributes to conduction by forming proton–electron pairs. Also, H/D isotope exchange studies confirmed protons as the dominant conduction carriers. Furthermore, H2 adsorption equilibrium modelling based on the Langmuir mechanism was applied to explain the H2 partial pressure dependence of conductivity. For the first time, the obtained model explains the experimentally obtained results both qualitatively and quantitatively. These findings represent new insights into surface protonics in H2 atmosphere.
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