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. CO 2 reduction is a significant step for carbon utilization. However, CO 2 reduction with less energy consumption has major challenges. In this study, CO 2 thermal reduction was demonstrated using nanocatalysts at temperatures lower than 1000 K, and the CO 2 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. CO 2 chemisorption occurred above 450 K and subsequent CO 2 reduction occurred above 500 K, which was expected based on the temperature-programmed reaction. CO 2 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 CO 2 into carbon products at 600 and 800 K. Therefore, an optimal condition of CO 2 reduction in the temperature range of 500-800 K. The highly active thermocatalyst achieved CO 2 reduction into CO and carbon products without any reducing agents even at an extremely low temperature (500 K). In summary, temperature-dependent CO 2 sorption and reduction were observed on the 10-nm nanocatalyst; CO 2 physical adsorption at 300-500 K, CO 2 chemisorption above 450 K, CO 2 reduction at 500-850 K, and CO 2 and CO releases above 800 K.