Thermochemical hydrogen production from water using reducible oxide materials: a critical review

This review mainly focuses on summarizing the different metal oxide systems utilized for water-splitting reaction using concentrated solar energy. Only two or three cyclic redox processes are considered. Particle size effect on redox reactions and economic aspect of hydrogen production via concentrated solar energy are also briefly discussed. Among various metal oxides system CeO2 system is emerging as a promising candidate and researchers have demonstrated workability of this system in the solar cavity-receiver reactor for over 500 cycles. The highest solar thermal process efficiency obtained so far is about 0.4 %, which needs to be increased for real commercial applications. Among traditionally studied oxides, thin-film ferrites looks more promising and could meet US Department of energy target of $2.42/kg H2 by 2025. The cost is mainly driven by high heliostat cost which needs to reduced significantly for economic feasibility. Overall, more work needs to be done in terms of redox material engineering, reactor technology, heliostat cost reduction and gas separation technologies before commercialization of this technology.