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Published July 28, 2010 | public
Journal Article

A thermochemical study of ceria: exploiting an old material for new modes of energy conversion and CO_2 mitigation

Abstract

We present a comprehensive thermodynamic and kinetic analysis of the suitability of cerium oxide (ceria) for thermochemical fuel production. Both portions of the two-step cycle, (i) oxygen release from the oxide at 1773 and 1873 K under inert atmosphere, and (ii) hydrogen release upon hydrolysis at 1073 K, are examined theoretically as well as experimentally. We observe gravimetric fuel productivity that is in quantitative agreement with equilibrium, thermogravimetric studies of ceria. Despite the non-stoichiometric nature of the redox cycle, in which only a portion of the cerium atoms change their oxidation state, the fuel productivity of 8.5–11.8 ml of H2 per gram of ceria is competitive with that of other solid-state thermochemical cycles currently under investigation. The fuel production rate, which is also highly attractive, at a rate of 4.6–6.2 ml of H_2 per minute per gram of ceria, is found to be limited by a surface-reaction step rather than by ambipolar bulk diffusion of oxygen through the solid ceria. An evaluation of the thermodynamic efficiency of the ceria-based thermochemical cycle suggests that, even in the absence of heat recovery, solar-to-fuel conversion efficiencies of 16 to 19 per cent can be achieved, assuming a suitable method for obtaining an inert atmosphere for the oxygen release step.

Additional Information

© 2010 The Royal Society. One contribution of 13 to a Discussion Meeting Issue 'Energy materials to combat climate change'. This work was funded by the National Science Foundation (CBET-0829114) and eSolar Inc. The authors are grateful for insightful discussions with Prof. Aldo Steinfeld, Dr Philip Gleckman and Dr Francesco Ciucci.

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023