Abstract Solar CO 2 /H 2 O splitting via two-step thermochemical cycles of metal oxides is a promising path for solar energy conversion to carbon-neutral, liquid hydrocarbons from virtually inexhaustible resources, water and (waste) carbon dioxide, with high theoretical efficiency potential. Cerium-based oxides have seen enormous interest and research efforts since they were proposed for this application, mainly due to their good stability at high temperatures and fast kinetics in redox reactions. The current state-of the-art review on the advancements of thermochemical cycles performed with the aid of cerium-based oxides is presented in this work, with emphasis on the latest developments during the last decade. Reaction principles, material modifications, reaction kinetics and finally solar reactors developed and operated are discussed in detail to provide a comprehensive understanding of the nature of the specific material and the factors impacting on the system efficiency. This efficiency depends on a combination of redox material/solar reactor/operation mode. With respect to the material issue, even though most studies have been targeted on improving the reduction conditions by suitable doping (e.g. Zr and Hf), the experience accumulated so far points to the direction of improving the oxidation step, provided the reduction step is performed below a critical, operationally feasible temperature. Thus the efficiency-optimal solar operation mode should be based on a trade-off between material reduction and oxidation performance and on another trade-off between solid and gas heat requirements and suitable recuperation strategies. The latter are highly dependent on the concept of solar reactor chosen and have to be demonstrated efficiently in real cyclic, field-test operation. The development of more effective oxygen removal strategies to lower the oxygen partial pressure during reduction may bring great improvement to efficiency.

中文翻译：

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太阳能燃料生产：基于铈的氧化物的两步热化学循环

摘要 太阳能通过金属氧化物的两步热化学循环分解 CO 2 /H 2 O 是将太阳能从几乎取之不尽的资源、水和（废物）二氧化碳中转化为碳中性液态碳氢化合物的一条有前途的途径，具有很高的理论效率。潜在的。自从铈基氧化物被提议用于该应用以来，它们引起了极大的兴趣和研究工作，主要是因为它们在高温下具有良好的稳定性和在氧化还原反应中的快速动力学。在这项工作中介绍了目前在铈基氧化物的帮助下进行的热化学循环进展的最新进展，重点是过去十年的最新发展。反应原理、材料改性、详细讨论了反应动力学以及最终开发和运行的太阳能反应堆，以全面了解特定材料的性质和影响系统效率的因素。该效率取决于氧化还原材料/太阳能反应器/操作模式的组合。关于材料问题，尽管大多数研究的目标是通过适当的掺杂（例如 Zr 和 Hf）来改善还原条件，但迄今为止积累的经验指出了改善氧化步骤的方向，前提是进行还原步骤低于临界的、可操作的温度。因此，效率最优的太阳能运行模式应该基于材料还原和氧化性能之间的权衡，以及固体和气体热需求与合适的回收策略之间的另一个权衡。后者高度依赖于所选择的太阳能反应堆的概念，并且必须在真实的​​循环、现场测试操作中得到有效证明。开发更有效的除氧策略以降低还原过程中的氧分压可能会大大提高效率。