Thermodynamic evaluation of cobalt-ferrite based redox reactions for solar thermochemical conversion of CO2 into fuels

The solar thermochemical conversion of carbon dioxide into synthetic fuels represents a promising pathway for mitigating anthropogenic CO₂ emissions while enabling the production of carbon neutral energy carriers. This study investigates the use of cobalt ferrite (CoFe₂O₄) as a redox-active metal oxide for two step solar thermochemical CO₂ splitting to produce carbon monoxide, a key component of syngas. Analysis showed that increasing εgg from 0.0 to 0.95, consistently strengthened heat recovery in the inert‑gas and oxygen cooling stages, which in turn sharply reduced the auxiliary heating loads for both Ar and CO₂. These reductions propagated through the system, lowering the total thermochemical energy requirement and the solar input needed to drive the cycle. At high recuperation levels (εgg ≥ 0.9), the typical penalty associated with higher inert‑gas flow rates was fully reversed, with larger flow rates requiring less solar energy than smaller ones. As a result, solar‑to‑fuel efficiency rose substantially with increasing εgg, reaching its highest values at elevated inert‑gas flow rates under strong recuperation. Overall, the findings demonstrate that highly effective gas‑to‑gas heat recuperation is the dominant lever for improving cycle performance, reducing solar energy demand, and shifting the optimal operating point toward higher inert‑gas throughput.