Study on spinel-type Fe–Ni–Co nanocomposite oxide structure mediating CO2 thermochemical conversion into green fuels

Solar-driven thermochemical CO2 reduction is a promising technology that enables the efficient conversion of CO2 into green fuels and chemicals. However, limited knowledge of the theory and technology, including active material characteristics, the redox cycling process, and reaction thermodynamics and kinetics, significantly affects efficiency and restricts large-scale applicability. This study investigated the thermochemical cycling characteristics of CO2-to-CO conversion and the redox performance of spinel-type Fe–Ni–Co nanocomposite oxide structures. The study also delved into the CO fuel formation reaction mechanisms and kinetics of oxygen carrier decomposition, as well as cyclic redox and thermal stability performances, considering different ratios of Fe–Ni–Co oxides and their mixtures. Among the materials investigated, NiFe2O4 nanoparticles doped with 20 % CoO and Ni0.8Co0.2Fe2O4 powder prepared using the sol-gel method exhibited better CO2 thermocatalytic conversion performance, with record-high CO yield of 1184.24 μmol/g and 1987.24 μmol/g, respectively. The study further revealed a more efficient Fe–Ni–Co composite oxide for CO2 thermochemical conversion through solar-driven thermochemical experimental testing, resulting in the highest cycle CO yields of 244 mL and 312 mL across 20%CoO doped NiFe2O4 and Ni0.8Co0.2Fe2O4 coated SiC media, respectively. These findings and methods provided comprehensive insights into the redox materials composition selectivity, synthesis, and CO2 thermochemical conversion performance assessments.