Promoting the NH3-SCR performance of Fe2O3-TiO2 catalyst through regulation of the exposed crystal facets of Fe2O3

Abstract

Iron oxide (Fe2O3)-based catalysts have garnered significant attention in the field of selective catalytic reduction with NH3 (NH3-SCR) due to their high thermal stability, N2 selectivity, low cost, and environmental friendliness. In this study, Fe2O3 catalysts with exposed {012}, {014}, and {113} facets were successfully synthesized using a hydrothermal method. Subsequently, TiO2 was loaded to construct Fe2O3-TiO2 catalysts with different crystal facets of Fe2O3. The results demonstrated that TiO2 was uniformly distributed on three different morphologies of Fe2O3. Among the catalysts, the Fe2O3{113}-TiO2 exhibited superior NOx removal capacity and a broader temperature operating range than Fe2O3{012}-TiO2 and Fe2O3{014}-TiO2. The promotion mechanism of NH3-SCR performance was determined by regulating the crystal facets of Fe2O3 in Fe2O3-TiO2 catalysts. The mechanism can be attributed to the improved redox properties, as well as the presence of additional active oxygens, surface acid sites, and adsorbed nitrate species on the Fe2O3{113}-TiO2 catalyst. In situ DRIFTS results indicated that the SCR reactions of Fe2O3-TiO2 catalysts with different crystal facets of Fe2O3 followed both the Langmuir-Hinshelwood and Eley-Rideal mechanisms. Furthermore, the Fe2O3{113}-TiO2 catalyst exhibited the improved reaction efficiency at both the Langmuir-Hinshelwood and Eley-Rideal pathways. This study provides novel insights on the influence of crystal planes on Fe2O3, which is important for optimizing Fe2O3-based NH3-SCR catalysts.