3D snowflake graphene modified α-MnO2 Catalyst: Enhancing the Low-Temperature catalytic activity for VOCs degradation

Manganese oxide is a promising catalyst for volatile organic compounds oxidation with merits of low cost, abundant valence states, diverse crystal forms and morphology, however, its catalytic activity at low temperature (<200 °C) is limited due to the poor dispersion and inferior electron transfer. To solve these problems, a novel 3D snowflake graphene is doped into α-MnO2 to fabricate rGO@α-MnO2 catalyst to enhance the catalytic activity at low temperature. Compared with α-MnO2, the rGO@α-MnO2 catalysts present larger specific surface area and pore volume, which facilitates the adequate contact reaction between active component and VOCs. The unique graphene electronic bridge promotes the electron transfer on rGO@α-MnO2, which results in higher concentration of surface defects and more surface adsorbed oxygen to the catalyst. The performance tests show that the catalyst doped with 4% 3D snowflake graphene has the best activity, which can achieve 90% toluene conversion at 155 °C, and even 100% toluene conversion with 80% CO2 selectivity at 200 °C. In particular, 4%rGO@α-MnO2 demonstrates excellent catalytic stability and moisture resistance, presenting similar catalytic performance after 5 cycles for both the dry and high relative humidity (RH = 85%) conditions. The excellent activity of 4%rGO@α-MnO2 can be attributed to the enhancement of toluene adsorption energy after graphene doping and the defect induced by the interface effect between graphene and (2 1 1) facet. In general, 3D snowflake graphene doping provides a convenient and cost-effective method to enhance the low-temperature activity of the α-MnO2 catalyst, presenting great application potential.