Indexed on: 20 Jan '17Published on: 20 Jan '17Published in: Environmental Science & Technology
Catalytic total oxidation of CH4 at a relatively low temperature over the precious metal (e.g., Pd-, Rh- or Pt)-based catalyst is believed to be a potential technology for the removal of greenhouse gas CH4. The traditional Pd-based catalysts for CH4 combustion reported in the literature tend to deactivate at high temperatures (> 600 °C), because the PdOx active phase is easily changed into aggregated metallic Pd nanoparticles (NPs). The high cost of Pd also limits its wide applications. In order to overcome such drawbacks, we herein design a novel pathway by introducing a certain amount of CoO to the supported Au-Pd alloy NPs to generate high-performance Au-Pd-xCoO/3DOM Co3O4 (x is the Co/Pd molar ratio) catalysts. The doping of CoO induced formation of PdO-CoO active sites, which was beneficial for the improvements in adsorption and activation of CH4 and catalytic performance. The Au-Pd-0.40CoO/3DOM Co3O4 sample performed the best, giving a T90 of 341 oC at a space velocity of 20 000 mL/(g h). The deactivation of the 3DOM Co3O4-supported Au-Pd, Pd-CoO, and Au-Pd-xCoO nanocatalysts resulted from the addition of water vapor was due to the formation and accumulation of hydroxyl on the surface of the catalyst, whereas the deactivation of the 3DOM Co3O4-supported Pd-CoO nanocatalyst at high temperatures (680-800 °C) might be due to the decomposition of the PdOx active phase into aggregated Pd0 NPs. The 3DOM Co3O4-supported Au-Pd-xCoO nanocatalysts exhibited better thermal stability and water tolerance ability, as compared to the 3DOM Co3O4-supported Au-Pd and Pd-CoO nanocatalysts. We believe that the supported Au-Pd-xCoO nanomaterials are promising catalysts in practical applications for organics combustion.