Feasibility of continuous water and carbon dioxide splitting via a pressure-swing, isothermal redox cycle using iron aluminates

Efficient solar thermochemical fuel production has been hindered by either solid–solid heat recuperation and material stability challenges associated with conventional temperature swing operation or low reactant conversion associated with isothermal operation. Increasing the oxidation pressure has emerged as a method for achieving efficient and practical solar-to-fuel conversion with certain redox mediators. When coupled with isothermal operation, pressure-swing redox cycling with iron aluminates eliminates irreversible heating penalties associated with large temperature swings while simultaneously enabling greater reactant conversion. However, remaining questions persist regarding 1) kinetics, 2) co-splitting capabilities, and 3) continuous processing prior to implementation beyond the lab scale. Here, we provide mechanistic insight on how pressure impacts the oxidation kinetics of iron aluminates, demonstrate syngas production with H 2 :CO ratios ranging from 1.3 ± 0.05 to 3.2 ± 0.25, and produce fuel continuously over an eight-hour period using dual fluidized bed reactors to evaluate the key considerations for large scale implementation. This work demonstrates the feasibility of a continuous solar thermochemical fuel production process via pressure-swing, isothermal redox cycling.