Two-step thermochemical cycles for CO2 reduction via Zn/ZnO and FeO/Fe3O4 redox
reactions are considered. The first, endothermic step is the thermal dissociation of the metal
oxide into the metal or a reduced valence metal oxide and O2 using concentrated solar
energy as the source of high-temperature process heat. The second, nonsolar, exothermic
step is the reaction of the reduced metal/metal oxide with CO2, yielding CO and/or C,
together with the initial form of the metal oxide that is recycled to the first step. Chemical …

Two-step thermochemical cycles for splitting CO2 with Zn/ZnO and FeO/Fe3O4 redox pairs
using concentrated solar energy are considered. Thermogravimetric-based kinetic analyses
were performed for the reduction of CO2 to CO with Zn and FeO. Both reactions are
characterized by an initial fast interface-controlled regime followed by a slow diffusion-
controlled regime, which are described using a shell− core kinetic model. In the interface-
controlled regime, a power rate law is applied with apparent activation energies 113.7 and …