Au/3DOM Co3O4: highly active nanocatalysts for the oxidation of carbon monoxide and toluene

Abstract

Three-dimensionally ordered macroporous Co₃O₄ (3DOM Co₃O₄) and its supported gold (xAu/3DOM Co₃O₄, x = 1.1–8.4 wt%) nanocatalysts were prepared using the polymethyl methacrylate-templating and bubble-assisted polyvinyl alcohol-protected reduction methods, respectively. The 3DOM Co₃O₄ and xAu/3DOM Co₃O₄ samples exhibited a surface area of 22–27 m² g⁻¹. The Au nanoparticles with a size of 2.4–3.7 nm were uniformly deposited on the macropore walls of 3DOM Co₃O₄. There were good correlations of oxygen adspecies concentration and low-temperature reducibility with catalytic activity of the sample for CO and toluene oxidation. Among 3DOM Co₃O₄ and xAu/3DOM Co₃O₄, the 6.5Au/3DOM Co₃O₄ sample performed the best, giving a T_90% (the temperature required for achieving a conversion of 90%) of −35 °C at a space velocity of 20 000 mL g⁻¹ h⁻¹ for CO oxidation and 256 °C at a space velocity of 40 000 mL g⁻¹ h⁻¹ for toluene oxidation. The effect of water vapor was more significant in toluene oxidation than in CO oxidation. The apparent activation energies (26 and 74 kJ mol⁻¹) over 6.5Au/3DOM Co₃O₄ were lower than those (34 and 113 kJ mol⁻¹) over 3DOM Co₃O₄ for CO and toluene oxidation, respectively. It is concluded that the higher oxygen adspecies concentration, better low-temperature reducibility, and strong interaction between Au and 3DOM Co₃O₄ were responsible for the excellent catalytic performance of 6.5Au/3DOM Co₃O₄.