Highly active and stable VOx/TiO2 nanosheets for low-temperature NH3-SCR of NO: Structure-directing role of support

Abstract

Low-temperature NH3-SCR over conventional catalysts based on V2O5/TiO2 is significantly limited by the narrow range of operating temperatures and poor activity at low temperatures. Herein, a novel catalyst consisting of defective TiO2 nanosheets supported vanadia (V/TNS) is successfully developed for the low-temperature NH3-SCR of NO. The V/TNS catalyst demonstrated excellent SCR performance, achieving over 95 % conversion with high N2 selectivity (>90 %) over a wide temperature range of 140–380 °C. Importantly, V/TNS was highly resistant to H2O and SO2 poisoning during 30 h of continuous operation, maintaining an NO conversion efficiency that exceeded 92 % at 180 °C. In contrast, a high-surface-area anatase TiO2 particle-supported catalyst (V/TiO2(A)) suffered from catalytic deactivation. Detailed characterization revealed that the TNS support, with its abundant surface defects and high surface area, improved vanadia dispersion and facilitated the formation of surface V4+ species and oxygen vacancies. These factors synergistically enhanced the adsorption and activation of NH3 and NOx, boosting catalytic performance. Moreover, the presence of SO2 had a notable inhibitory effect on the adsorption and activation of NH3 and NOx and their reactions on V/TiO2(A), while these detrimental effects were considerably mitigated on V/TNS.