Different morphologies on Cu–Ce/TiO2 catalysts for the selective catalytic reduction of NOx with NH3 and DRIFTS study on sol–gel nanoparticles

Abstract

The copper–cerium binary oxide catalysts supported by titanium dioxide with nanosphere core–shell structures, nanotube (TNT) core–shell structures, impregnation (imp) nanoparticles and sol–gel nanoparticles were prepared for NH₃-SCR of NO_x under medium-low temperature conditions. The effect of different morphologies on the Cu–Ce/TiO₂ catalysts was comprehensively studied through physicochemical characterization. The results showed that the sol–gel nanoparticles exhibited 100% NO_x reduction efficiency in the temperature range of 180–400 °C. Compared with the other catalysts, the sol–gel nanoparticle catalyst had the highest dispersion and lowest crystallinity, indicating that morphology played an important role in the NH₃-SCR of the catalyst. The in situ DRIFTS study on the sol–gel nanoparticle catalyst shows that cerium could promote Cu²⁺ to produce abundant Lewis acid sites, which would significantly increase the adsorption reaction of ammonia on the catalyst surface, thereby promoting the occurrence of the Eley–Rideal (E–R) mechanism. With the Ce–Ti interaction on the atomic scale, the Ce–O–Ti structure enhanced the redox properties at a medium temperature. In addition, cerium oxide enhances the strong interaction between the catalyst matrix and CuO particles. Therefore, the reducibility of the CuO species was enhanced.