Temperature-dependent CO ₂ sorption and thermal-reduction without reactant gases on BaTiO ₃ nanocatalysts at low temperatures in the range of 300–1000 K

Carbon utilization techniques to mitigate the impact on global warming are an important field in environmental science. CO₂ reduction is a significant step for carbon utilization. However, CO₂ reduction with less energy consumption has major challenges. In this study, CO₂ thermal reduction was demonstrated using nanocatalysts at temperatures lower than 1000 K, and the CO₂ sorption and reduction mechanisms within the temperature range of 300-1000 K were evaluated. The physical adsorption on nanocatalysts with a crystal size of 7.4 ± 0.4 nm (10 nm-nanocatalysts) majorly occurred at 300 K and was considerably decreased beyond that temperature. CO₂ chemisorption occurred above 450 K and subsequent CO₂ reduction occurred above 500 K, which was expected based on the temperature-programmed reaction. CO₂ reduction decreased above 900 K by the deactivation of the 10-nm nanocatalyst as a result of its crystal growth. The transmission electron microscopy images also indicated the complete reduction of CO₂ into carbon products at 600 and 800 K. Therefore, an optimal condition of CO₂ reduction in the temperature range of 500-800 K. The highly active thermocatalyst achieved CO₂ reduction into CO and carbon products without any reducing agents even at an extremely low temperature (500 K). In summary, temperature-dependent CO₂ sorption and reduction were observed on the 10-nm nanocatalyst; CO₂ physical adsorption at 300-500 K, CO₂ chemisorption above 450 K, CO₂ reduction at 500-850 K, and CO₂ and CO releases above 800 K.