In Situ Regeneration of Au Nanocatalysts by Atmospheric-Pressure Air Plasma: Regeneration Characteristics of Square-Wave Pulsed Plasma

Abstract

Atmospheric-pressure air plasma, powered by alternating current (AC) sine-wave high voltage, can in-situ regenerate deactivated Au nanocatalysts during CO oxidation, but it needs high-humidity air as the discharge gas. To overcome the limitation on humidity for in-situ regeneration of air plasma, a square-wave pulsed plasma is applied in this work. Differently from the AC plasma, the pulsed plasma exhibits excellent regeneration performance at any humidity. Further, surface carbonate decomposition, nitrogen oxides poisoning species and electric discharge of the pulsed plasma regeneration are investigated. For the pulsed plasma regeneration at any humidity, the evolution of CO2 concentration with the regeneration time almost keeps the same profile, featuring zero-order kinetics for the carbonate decomposition; on the other hand, whether in the gas phase or on the catalyst surface, there are no formation of poisoning nitrogen oxides. The pulsed plasma at any humidity has the powerful ability in carbonate decomposition and simultaneously prevents the formation of poisoning nitrogen oxides, which is ascribed to its highly centralized energy deposition with high instantaneous power and long interval of instantaneous power. For practical application, normal air is also confirmed to be qualified for the pulsed plasma regeneration.