Regeneration of deactivated Au/TiO2 nanocatalysts during co oxidation by using in-situ O2 and N2/O2 plasma

Summary form only given. Supported gold (Au) nanocatalysts have attracted much attention due to their high activities in CO oxidation at low-temperature. While the deactivation of gold catalysts during the reaction limits their practical use. Two major reasons for the deactivation were put forward and accepted in general, i.e. agglomeration of gold particles and accumulation of carbonate-like species. The agglomeration of gold particles may cause irreversible and weak deactivation. In most cases, the accumulation of inactive surface carbonate species on catalyst during CO oxidation may lead to catalyst activity loss. This type of deactivation could be reversibly regenerated through post heat-treatment, however, which brings a side effect or issue of irreversible gold particles aggregation during heat-treatment. In this paper, non-thermal plasma (NTP) technologies were used for in-situ regeneration of the deactivated gold catalysts at low temperature. It is the first time to report in-situ regeneration of the deactivated Au/TiO₂ catalysts during CO oxidation by O₂ (with presence or absence of N₂) plasma. It has been demonstrated that pure O₂ plasma could reversibly regenerate the deactivated Au/Ti O₂ catalysts for CO oxidation. However, from practical point of view, potentially applying air instead of pure O₂ is more favorable. Thus the effect of N₂ content on the catalyst regeneration was investigated. It was found that N₂ addition would cause an extra poisoning effect. At N₂ content of 10%, the extra poisoning effect is the worst and becomes much weaker at the concentration of N₂ in air. The formation of surface poisoning species [NO_y]_s was proposed to explain the catalyst poising during regeneration using N₂/ O₂ plasma.