Solar Redox Cycling of Ceria Structures Based on Fiber Boards, Foams, and Biomimetic Cork-Derived Ecoceramics for Two-Step Thermochemical H2O and CO2 Splitting


Solar thermochemical conversion of H2O and captured CO2 is considered for the production of high-value solar fuels and CO2 valorization, using nonstoichiometric oxygen-exchange redox materials. This work aims to compare the thermochemical cycle performance of different ceria structures, including biomimetic cork-templated ceria (CTCe), ceria foams (CeF), and ceria bulk fiber boards (CeFB), to study the effect of the morphology on fuel production from two-step H2O and CO2 splitting via solar redox cycling. The considered materials underwent thermochemical cycles in a directly irradiated solar reactor under various operating conditions. Typically, a thermal reduction at 1400 degrees C under Ar at atmospheric pressure, using concentrated solar energy, was carried out followed by an oxidation step with H2O or CO2 between 800 and 1050 degrees C. The comparison of the fuel production rate and yield from the reactive materials highlighted the importance of the material thermal stability during cycling. CTCe and CeF showed good O-2 and fuel production stability over repeated cycles, while CeFB exhibited a decrease of the production because of sintering and thermal gradient due to its low thermal conductivity. Biomimetic CTCe showed a higher fuel production rate compared to the other investigated materials, explained by the favorable microstructure of the cork-based ceramic. The morphology obtained from the cork structure led to the improvement of the redox activity, demonstrating the relevance of studying this material for thermochemical H2O and CO2 splitting cycles. In addition, the impact of the operating conditions was investigated. A decrease of the starting oxidation temperature, an increase of the CO2 molar fraction (lower CO/CO2 ratio), or a high total gas flow rate favoring gas product dilution had a beneficial impact on the CO (or H-2) production rate.



subject category

Energy & Fuels; Engineering


Haeussler, A; Abanades, S; Oliveira, FAC; Barreiros, MA; Caetano, APF; Novais, RM; Pullar, RC

our authors


The experimental setup used in this work was partially funded by the French National Agency for Research (ANR, SUNFUEL project, contract no. ANR-16-CE06-0010). Transnational access to CSP facilities and research infrastructures of CNRS-PROMES through SFERA-III project (grant agreement no. 823802) is also acknowledged. The authors thank R. Garcia (PROMES) for solar reactor design. This work was also supported by Fundacao para a Ciencia e a Tecnologia (FCT), through the H2CORK project, grant no. PTDC/CTM-ENE/6762/2014 as well as POCI-01-0145-FEDER-016862. R.M.N. was supported by a postdoc research fellowship and FCT grant CEECIND/00335/2017. Thanks are also due to Zircar Zirconia, Inc., Amorim Cork Composites, S.A. and Flexipol -Espumas Sinte ' ticas S.A. for donating the ceria fiber boards, cork samples, and the PU foams, respectively. R.C.P. wishes to thank FCT grant IF/00681/2015 for supporting this work. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 and UIDP/50011/2020, financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement. The financial support provided by INIESC -National Research Infrastructure for Concentrated Solar Energy through contract ALT20-03-0145-FEDER-022113 is also acknowledged.

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