Mechanism of selective catalytic reduction of NOx with NH3 over CeO2-TiO2: Insight from in-situ DRIFTS and DFT calculations

Abstract

The reaction mechanism over CeO2-TiO2 catalyst was investigated using in-situ DRIFTS spectra and density functional theory (DFT) calculations. DRIFTS results revealed that the SCR reactions on CeO2-TiO2 catalyst followed both E-R and L-H mechanisms. In the E-R mechanism, NH2NO species was considered as the reaction intermediate that decomposed into H2O and N2. In the L-H mechanism, only adsorbed NO2 species reacted with NH3 to generate H2O and N2. Based on the two mechanisms, the corresponding adsorption energy, activation energy barrier, and reaction heat in the process of NH3 adsorption and activation, NH2NO formation and decomposition, O2 dissociation, and NO oxidation were calculated by DFT. By combining the DRIFTS and DFT results, the detailed reaction pathways over CeO2-TiO2 catalyst were obtained finally.