Alumina doped Fe2O3 foams by freeze-casting for redox cycling applications

Hydrogen is the next energy vector for a decarbonization society but industrial production is still methane-based. The Steam Iron Process (SIP) could provide a carbon-free production and safety storage option. Here, we show that a Fe2O3-3 wt% of Al2O3 foams created by freeze-casting withstand 10 redox cycles at different temperatures with no reduction in performance or pore shrinking. The use of stearic acid as a dispersant agent/binder produces the porous structure enhancement of the foam and promotes the early reduction of the hematite phase during foam sintering. The Al2O3 incorporation was detected as a solid solution in the Fe2O3 phase at the particle surface. This result is relevant as correlated the positive values of the zeta potential observed. Freeze-casted foams could improve long-term redox performances combining a unique tailored interconnected pore structure with a specific chemical composition.