Materials Science, California Institute of Technology, , MC 309-81, Pasadena, CA 91125, USA.
Philos Trans A Math Phys Eng Sci. 2010 Jul 28;368(1923):3269-94. doi: 10.1098/rsta.2010.0114.
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 H(2) 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.
我们提出了一个全面的热力学和动力学分析，以评估氧化铈（CeO2）作为热化学燃料生产的适宜性。两步循环的两个部分，（i）在惰性气氛下于 1773 和 1873 K 时从氧化物中释放氧气，以及（ii）在 1073 K 下水解时释放氢气，都进行了理论和实验研究。我们观察到的重量燃料生产率与平衡、CeO2 的热重研究定量一致。尽管氧化还原循环具有非化学计量性质，其中只有部分铈原子改变其氧化态，但 8.5-11.8 ml 的 H2 每克 CeO2 的燃料生产率与目前正在研究的其他固态热化学循环相当。燃料生产速率也非常有吸引力，为每分钟每克 CeO2 4.6-6.2 ml 的 H2，发现其受到表面反应步骤的限制，而不是通过氧在固态 CeO2 中的双极体扩散来限制。对基于 CeO2 的热化学循环的热力学效率的评估表明，即使没有热量回收，假设采用一种合适的方法获得释放氧气步骤所需的惰性气氛，也可以实现 16%至 19%的太阳能到燃料的转换效率。
