Microenvironment engineering for enhancing catalytic active sites for the CO oxidation reaction

The removal of carbon monoxide (CO) from sintering flue gases remains a significant challenge in industrial gas purification, requiring efficient catalytic systems. This study explores the use of TiO₂ synthesized under supercritical conditions in copper-based catalysts for low-temperature CO oxidation. Experimental results showed enhanced catalytic activity, with complete CO conversion at 120 °C, primarily due to a higher Cu⁺ concentration in the catalyst. Characterization techniques (XPS, EPR, CO-DRIFT) confirmed a substantial increase in the Cu⁺ ratio in Cu/sc-TiO₂ (78 %) compared to Cu/TiO₂ (71 %) before thermal treatment. Additionally, the Cu/sc-TiO₂-A catalyst exhibited smaller particle size and better dispersion, which contributed to the elevated Cu⁺ ratio after preheating. Thermal treatment increased the Cu⁺ ratio by 11 % in Cu/sc-TiO₂-A, compared to just 3 % in Cu/TiO₂-A, leading to a final Cu⁺ ratio of 89 %, which enhanced catalytic activity. DRIFT and TPSR analyses indicated that the Cu/sc-TiO₂ catalyst generated CO during heat treatment, creating a micro-reduction environment that optimized copper valence states and active sites. This study highlights the potential of continuous hydrothermal flow synthesis for modulating catalyst valence states in industrial applications.