Due to the requirement to develop carbon-free energy, solar energy conversion into chemical energy carriers is a promising solution. Thermochemical fuel production cycles are particularly interesting because they can convert carbon dioxide or water into CO or H2 with concentrated solar energy as a high-temperature process heat source. This process further valorizes and upgrades carbon dioxide into valuable and storable fuels. Development of redox active catalysts is the key challenge for the success of thermochemical cycles for solar-driven H2O and CO2 splitting. Ultimately, the achievement of economically viable solar fuel production relies on increasing the attainable solar-to-fuel energy conversion efficiency. This necessitates the discovery of novel redox-active and thermally-stable materials able to split H2O and CO2 with both high-fuel productivities and chemical conversion rates. Perovskites have recently emerged as promising reactive materials for this application as they feature high non-stoichiometric oxygen exchange capacities and diffusion rates while maintaining their crystallographic structure during cycling over a wide range of operating conditions and reduction extents. This paper provides an overview of the best performing perovskite formulations considered in recent studies, with special focus on their non-stoichiometry extent, their ability to produce solar fuel with high yield and performance stability, and the different methods developed to study the reaction kinetics.

Thermochemical cycle

Solar fuel

Stoichiometry

Energy transformation

10.3390/catal8120611

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Citations (77)

Recent progress on ceria doping and shaping strategies for solar thermochemical water and CO<sub>2</sub> splitting cycles

AIMS Materials Science (2019)

Anita Haeussler Stéphane Abanades Julien Jouannaux Martin Drobek A. Ayral

Thermochemical redox cycling for either water or CO₂ splitting is a promising strategy to convert solar energy into clean fuels. Such splitting reaction can convert water and recycled CO₂ into H₂ and CO respectively, the building blocks for the preparation of various synthetic liquid fuels. Attractively, CO₂ is valorized in this way and can be used as a carbon-neutral fuel. However, the efficiency of the solar thermochemical process has to be improved to achieve an economically viable fuel production. For this purpose, an optimization of the reactive materials regarding both their chemical activity and long-term stability is a key requirement. To date, ceria is considered as the benchmark material for thermochemical redox cycles. Indeed, it is able to maintain a single cubic fluorite phase during thermal cycling over a large range of oxygen non-stoichiometry and also provides thermodynamically favorable oxidation. However, it suffers from a high reduction temperature and a low reduction extent. Several doping strategies of ceria have been developed to increase its redox activity and long-term performance stability. This paper provides an overview of the efforts made to enhance the thermochemical performance of ceria by investigation of dopant incorporation and material shaping for designed morphologies and microstructures.

Thermochemical cycle

Stoichiometry

Solar fuel

10.3934/matersci.2019.5.657

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Citations (37)

Solar thermochemical fuel production from H2O and CO2 splitting via two-step redox cycling of reticulated porous ceria structures integrated in a monolithic cavity-type reactor

Energy (2020)

Anita Haeussler Stéphane Abanades A. Julbe Julien Jouannaux B. Cartoixa

Thermochemical cycle

Oxidizing agent

Solar fuel