Enhancement mechanism of n-n homojunction δ/α-MnO2 with fast electron transfer characteristics for efficient photothermal synergistic catalytic oxidation of propane

The construction of isotype homojunctions composed of the same semiconductor can improve the photoelectrochemical properties, adsorption and catalytic properties of the catalysts, which is important for the enhancement effect in photothermal synergistic catalytic oxidation (PTSCO) system. Herein, a series of homojunctions with δ- and α-phase MnO2 catalysts were designed and synthesized for propane oxidation in PTSCO system. The 4-δ/α exhibited outstanding propane catalytic oxidation performance (T90 = 198 ℃, Ea = 20.56 kJ·mol−1, remarkable water resistance, long-time stability and recycling performance) due to the rich oxygen vacancy, higher low-temperature redox, increased surface acidity, fast transfer and effective separation of photogenerated electron-holes. Additionally, a photothermal synergistic mechanism was proposed based on reaction kinetics, active species detection, density functional theory (DFT) and in-situ DRIFTs. This work presents a novel method for the design and preparation of homojunction catalysts. Furthermore, it explains the synergistic mechanism of the PTSCO system.