Preparation of different morphologies of Au/α-MnO₂ catalyst for oxidation of carbon monoxide and toluene

1-D nanosized rod-like, wire-like, and tubular α-MnO₂ (xAu/α-MnO₂,x=2%,4%,8%,10%) were prepared using the hydrothermal and PVA-protected NaBH₄ reduction methods at different temperatures with KMnO₄ and/or MnSO₄ as Mn source, respectively. It is shown that the α-MnO₂ in xAu/α-MnO₂ was tetragonal in crystal structure, surface area of α-MnO₂ nanorods, nanowires, and nanotubes was in the range of 48.4-114.0 m ²/g. The 4%Au/α-MnO₂ sample possessed the highest adsorbed oxygen species concentration and the best low-temperature reducibility, thus showing the highest catalytic activity: the T_50% and T_90% (temperatures required for achieving reactant conversions of 50% and 90%) were 11.4 and 16.3 ℃ for CO oxidation, and 210 and 225 ℃ for toluene oxidation at a space velocity of 20 000 mL/(g ·h), respectively. Based on the characterization results and activity data, it is concluded that the better low-temperature reducibility, higher oxygen adspecies concentration, highly dispersed Au NPs, and stronger interaction between Au NPs and MnO₂ nanorods were the main factors influencing the catalytic performance of 4%Au/α-MnO₂.