Insights into the effects of Mn and Ni on Pt-modified sulfated CeO2 catalysts for NO removal

Abstract

Nitric oxide (NO), a major atmospheric pollutant and a precursor to haze, can be removed using the denitration catalyst. Mn and Ni are commonly used as denitration catalyst additives owing to their adsorption abilities for NO and ammonia (NH₃). In this study, we synthesized Mn- and Ni-loaded Pt-modified sulfated cerium oxide (PtSCe) catalysts using an impregnation method and explored the effects of these elements. The results revealed that the two elements had contrasting effects on the denitration activity of the catalysts. Mn improved the water vapor and sulfur resistance of the PtSCe sample by increasing the concentration of weak acid sites, enhancing the redox ability, and increasing the content of surface-adsorbed oxygen. The elevation in oxygen vacancies, stimulated by the presence of Ce³⁺ and Mn³⁺, swiftly replenished the reactive oxygen species, thereby sustaining the high denitration efficiency of the MnPt/SCe sample. Active sites on the catalyst surface included NH₃ adsorbed on Lewis acid sites, NH⁴⁺, and –NH₂, along with bridging, monodentate, and bidentate nitrate groups. Regarding the catalyst reaction mechanism, we determined that the selective catalyst reduction of NH₃-SCR over MnPt/SCe followed both the Eley–Rideal and Langmuir–Hinshelwood mechanisms. These findings offer crucial insights into the intricate relationship between metals, sulfates, and carrier molecules, thus providing implications for future catalyst design.