Evaluating the Performance of Solar Thermochemical Two-Step CO2 Splitting Via a Cavity-Receiver Reactor

Carbon dioxide is an important factor that severely affects the quality of environment. There are tremendous technologies that have been proposed or applied in the CO₂ conversion process. Solar thermochemical process provides an attractive approach that utilizes the most common solar radiation as the driving force to motivate the reaction between CO₂ and metal oxides. By two-step redox process, the incoming CO₂ can be transformed to CO for further applications. Among the diversified metal oxide redox pairs, CeO₂/CeO_2-δ shows an anticipated performance, due to its fast redox kinetics, high crystallographic stability of a wide range of reacting oxygen non-stoichiometry, and relatively high oxygen solid-state conductivity. In this work, the two-step solar thermochemical CO₂ splitting process is simulated in a cavity-receiver reactor with improved geometrical design of inlet and outlet. The metal oxide catalyst CeO₂ is presented as a reticulated porous ceramic foam in the reactor. By applying different input solar power, the performance of O₂ evolution from high temperature reduction is evaluated. With different mass flow of CO₂, the performance of low temperature oxidation is compared. By the analysis of the radiative absorption and temperature distribution of the cavity-receiver reactor with the relation of catalyst load and CO₂ inlet flow rate, a higher solar-to-fuel energy conversion efficiency can be derived.