Facial controlled synthesis of Pt/MnO2 catalysts with high efficiency for VOCs combustion

Abstract

Two sets of experiments were initially implemented to explore the best impregnation method and the best morphology substrate. In the first case, Pt/MnO₂-r-WI catalyst showed a better performance than that of Pt/MnO₂-r-IW. The test results illustrated that Wetness Impregnation (WI) could enhance the dispersion of Pt, ratios of Mn⁴⁺/Mn³⁺, O_ads/O_latt and Pt⁴⁺/Pt⁰ as compared to those of Incipient Wetness Impregnation (IW). In the other method, MnO₂-s catalyst displayed a higher catalytic efficiency than that of MnO₂-r because the nanosphere morphology had larger BET surface area and pore volume to attract Pt atoms and toluene molecules. Therefore, the Pt/MnO₂-s-WI catalyst was obtained and showed the best activity with low-temperature redox capability and oxygen mobility. It could eliminate toluene (T₉₀) at a low temperature of 205 °C and remain stable over 150 h. effects of calcination temperature, toluene concentration and gas hourly space velocity (GHSV) were also investigated herein. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was also implemented to explore the reaction mechanism. It demonstrated that toluene was firstly adsorbed over Pt^δ+ on the surface before being oxidized to CO₂ and H₂O. The whole procedure follows the Mars-van Krevelen mechanism. This work gives a comprehensive understanding of the heterogeneous catalysis mechanism.