Self-Propagating High-Temperature Synthesis of Water-Splitting Mixed Iron Oxides for Solar Hydrogen Production

摘要

Self-propagating High-temperature Synthesis (SHS) was employed for the synthesis of mixed iron oxide-based redox materials to be used for hydrogen production from water-splitting via thermochemical cycles. The conditions for the synthesis of particular phases by SHS reactions between iron metal and dopant oxide powders were optimized. The flexibility of the synthesis method was demonstrated: by “fine-tuning” the synthesis parameters (synthesis atmosphere, kind and stoichiometry of dopants) and carefully controlling the exothermicity of the reactions, a whole range of different products was synthesized: from singe-phase, doped spinel ferrites (A_xZn_yFe_(1-x-y))Fe_2O_4 to “oxygenlean” doped wustites (A_x'Zn_y'Fe_(1-x'-y'))O. Such SHSsynthesized powders have demonstrated superior watersplitting activity performance attributed to their high content of structural defects. The water-splitting activity was found to depend on the amount of bivalent iron in the product powder. The materials were coated on refractory ceramic honeycomb monoliths optimized to absorb solar irradiation and tested in several solar campaigns.