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arXiv · 1309.0064

An electrical conductivity relaxation study of oxygen transport in samarium doped ceria

Chirranjeevi Balaji Gopal·Sossina M. Haile
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Abstract

The efficacy of the electrical conductivity relaxation (ECR) technique for investigating the oxygen transport properties of mixed conducting oxides has been evaluated. Fifteen mol% samarium doped ceria (SDC15), for which approximate values of the two principal transport properties, bulk oxygen diffusivity, $D_{Chem}$, and surface reaction rate constant, $k_S$, can be found in the literature, was chosen as the benchmark material against which to validate the methodology. Measurements were carried out at temperatures between 750 $^\circ$C and 850 $^\circ$C and over a wide range of oxygen partial pressures. An unexpectedly high p-type electronic transference number enabled ECR measurements under oxidizing conditions. A systematic data analysis procedure was developed to permit reliable extraction of the kinetic parameters even in the general case of simultaneous bulk and surface limitation. The $D_{Chem}$ from this study showed excellent qualitative and quantitative agreement with expected values, falling in the range from $\sim 2\times10^{-5}$ to $2\times10^{-4}$ cm$^2$/s. The surface reaction constant under H$_2$/H$_2$O mixtures also showed good agreement with literature results. Remarkably, this value increased by a factor of 40 under mixtures of CO/CO$_2$ or O$_2$/Ar. This observation suggests kinetic advantages for production of CO rather than H$_2$ in a two-step solar-driven thermochemical process based on samarium doped ceria.

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Chirranjeevi Balaji Gopal, Sossina M. Haile. 2014-01-02. An electrical conductivity relaxation study of oxygen transport in samarium doped ceria. https://arxiv.org/abs/1309.0064

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