Fabrication of surface oxygen vacancy on α-MnO2 via calcination atmosphere for catalytic oxidation of toluene at low temperature

Abstract

Defect engineering is recognized as an effective strategy for constructing efficient catalysts for the oxidation of volatile organic compounds (VOCs). In this study, a series of Mn-based catalysts were synthesized via a hydrothermal method, followed by modulation of surface oxygen vacancies through the adjustment of the roasting atmosphere, and were subsequently applied in the catalytic combustion of toluene. Activity tests showed that the α-MnO₂ catalyst calcined under argon atmosphere had the best catalytic performance, which was able to achieve 90 % toluene conversion at 235 °C under a weight hourly space velocity (WHSV) of 120,000 mL·g⁻¹·h⁻¹. In addition, the catalyst also maintained high toluene removal efficiency at 248 °C, even when the WHSV was increased to 150,000 mL·g⁻¹·h⁻¹. Characterization results demonstrated that oxygen vacancies on the catalyst surface can be effectively regulated by modifying the roasting atmosphere. The introduction of oxygen vacancies enhanced the low-temperature reduction ability and oxygen mobility of catalysts, thus improving the catalytic performance. Besides, higher Mn³⁺/Mn⁴⁺ and O_ads/O_latt ratios were also critical factors for high activity. Therefore, this work provides a simple and feasible defect-constructing approach for the fabrication of oxygen vacancies on the MnO₂ catalyst surface by controlling the roasting atmosphere.