Porous Co3O4 nanowires and nanorods: Highly active catalysts for the combustion of toluene

Porous Co3O4 nanowires and nanorods (Co3O4-HT, Co3O4-HT-PEG, Co3O4-HT-CTAB, and Co3O4-ME-CTAB, respectively) have been fabricated via the hydrothermal or microemulsion route in the absence and presence of polyethylene glycol (PEG) or cetyltrimethylammonium bromide (CTAB), respectively. Physicochemical properties of the materials were characterized by means of numerous techniques, and their catalytic activities for toluene combustion were evaluated. It is shown that Co3O4-HT-PEG and Co3O4-HT-CTAB displayed a porous nanowire-like morphology, whereas Co3O4-ME-CTAB exhibited a porous nanorod-like shape. The porous Co3O4 samples (surface area = 47–52 m2/g) possessed much higher surface oxygen adspecies concentrations and much better low-temperature reducibility than the nonporous counterpart. The Co3O4-HT-CTAB sample showed the highest catalytic performance (T50% = 195 and T90% = 215 °C at a space velocity of 20,000 mL/(g h)). It is concluded that the excellent catalytic performance of Co3O4-HT-CTAB was associated with its higher surface area and surface oxygen species concentration, and better low-temperature reducibility.