In situ growth of Co3O4 nano-dodecahedeons on In2O3 hexagonal prisms for toluene catalytic combustion

In this paper, in situ growth of Co3O4 nano-dodecahedra on In2O3 hexagonal prisms were synthesized via pyrolysis of ZIF-67/MIL-68. Interestingly, the amount of Co3O4 dodecahedra on In2O3 hexagonal prisms was regularly regulated and controlled. In detail, four Co3O4/In2O3 catalysts with various Co/In molar ratio were prepared, including Co4In1 (Co/In molar ratio was 4:1), Co2In1 (Co/In molar ratio was 2:1), Co1In1 (Co/In molar ratio was 1:1), Co0.5In1 (Co/In molar ratio was 0.5:1). The catalytic performance of Co3O4/In2O3 catalysts was systematically investigated for toluene combustion. It could be noted that the Co2In1 sample exhibited the superior catalytic performance, and the temperatures for 90% toluene conversion (T90) was 182 °C. Furthermore, the toluene conversion of Co2In1 sample had no significant decrease at 178 °C for 15 h, indicating that it presented superior stability for toluene oxidation reaction. Through various characterizations, it was verified that the Co/In molar ratio of Co3O4/In2O3 catalyst could obviously alter the surface atomic ratio of Co3+/(Co3+ + Co2+), BET surface area, the number of surface adsorbed oxygen, the interaction between In2O3 and Co3O4 of CoInOx catalysts and so on. The lots of surface adsorbed oxygen, strong interaction between In2O3 and Co3O4 would promote the catalytic oxidation of toluene. Especially, we discovered that the catalytic activity of Co3O4/In2O3 was obviously improved with the increase of Co3+/(Co3+ + Co2+) surface atomic ratio. Keywords: In-situ growth, ZIF-67/MIL-68, Co3O4/In2O3, Co/In molar ratio, Toluene catalytic combustion