α-Fe2O3/MnO2 heterojunction catalysts with enhanced low-temperature activity for selective N2 production in NH3-SCR

Current commercial catalysts remain inadequate for industrial kiln operations under low-temperature exhaust conditions. Consequently, the development of catalysts with enhanced low-temperature NH3-SCR activity and elevated NOx reduction efficiency has become a strategic focus. In this study, a cryptomelane-type MnO2 catalyst was synthesized through a one-step hydrothermal method, and an in-situ heterostructure was developed via alpha-Fe2O3 doping to enhance N2 selectivity in NH3-SCR. The results demonstrate that alpha-Fe2O3 incorporation elevates Mn4+ concentration, thereby promoting NH3 adsorption and NH4+ formation, which synergistically accelerates NO reduction. Additionally, surface-active oxygen species and Br & oslash;nsted acid sites initially increased with alpha-Fe2O3 content but diminished when exceeding an optimal doping level. Under simulated flue gas conditions (500 ppm NO, 1000 ppm NH3, 5 % O2, 5 % H2O, and a gas hourly space velocity of 36,000 h-1), the 5 wt % alpha-Fe2O3-loaded catalyst exhibited enhanced low-temperature catalytic performance, achieving 82 % N2 selectivity at 175 degrees C, compared to 74 % at 200 degrees C. The alpha-Fe2O3/MnO2 catalyst demonstrated exceptional catalytic activity at low temperatures, suggesting a promising strategy for industrial flue gas denitrification.