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

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 {0 1 2}, {0 1 4}, and {1 1 3} 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{1 1 3}-TiO₂ exhibited superior NO_x removal capacity and a broader temperature operating range than Fe₂O₃{0 1 2}-TiO₂ and Fe₂O₃{0 1 4}-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{1 1 3}-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{1 1 3}-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.