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Review ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Chem. | doi: 10.3389/fchem.2019.00601

A review of solar thermochemical CO2 splitting using ceria-based ceramics with designed morphologies and microstructures

 Robert Pullar1*,  Rui Novais1, Ana Caetano1,  Alexandra Barreiros2, Stéphane Abanades3 and  Fernando Oliveira2
  • 1University of Aveiro, Portugal
  • 2Laboratório Nacional de Energia e Geologia, Portugal
  • 3UPR8521 Laboratoire procédés, matériaux, énergie solaire (PROMES), France

This review explores the advances in the synthesis of ceria materials with specific morphologies or porous macro- and microstructures for the solar-driven production of carbon monoxide (CO) from carbon dioxide (CO2). As the demand for renewable energy and fuels continues to grow, there is a great deal of interest in solar thermochemical fuel production (STFP), with the use of concentrated solar light to power the splitting of carbon dioxide. This can be achieved in a two-step cycle, involving the reduction of CeO2 at high temperatures, followed by oxidation at lower temperatures with CO2, splitting it to produce CO, powered by concentrated solar power (CSP) to provide the high reaction temperatures of typically up to 1500 ºC. Since cerium oxide was first explored as a solar-driven redox catalyst in 2006, and to specifically split CO2 in 2010, there has been an increasing interest in this material. The solar-to-fuel conversion efficiency is influenced by the material composition itself, but also by the material morphology that mostly determines the available surface area for solid/gas reactions (the material oxidation mechanism is mainly governed by surface reaction). The diffusion length and specific surface area affect, respectively, the reduction and oxidation steps. They both depend on the reactive material morphology that also substantially affects the reaction kinetics and heat and mass transport in the material. Accordingly, the main relevant options for materials shaping are summarised. We explore the effects of microstructure and porosity, and the exploitation of designed structures such as fibres, 3-DOM (three-dimensionally ordered macroporous) materials, reticulated and replicated foams, and the new area of biomimetic/biomorphous porous ceria catalysts produced from natural and sustainable templates such as wood or cork, sometimes known as ecoceramics.

Keywords: Concentrated solar power (CSP), ceria, Thermochemical cycle, microstructure, 3-DOM, foam, Fibre, CO2 splitting, Ecoceramics, CORK, reticulated prorous ceramics (RPC), CeO2, solar fuels, Biomimetic, biomorphic

Received: 22 Nov 2018; Accepted: 15 Aug 2019.

Edited by:

Jean-Michel Lavoie, Université de Sherbrooke, Canada

Reviewed by:

Jong Hoon Joo, Chungbuk National University, South Korea
Wojciech Lipinski, Australian National University, Australia  

Copyright: © 2019 Pullar, Novais, Caetano, Barreiros, Abanades and Oliveira. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Robert Pullar, University of Aveiro, Aveiro, Portugal, rpullar@ua.pt