Role of Structural Defects in MnOx Promoted by Ag Doping in the Catalytic Combustion of Volatile Organic Compounds and Ambient Decomposition of O3.

Abstract

Manganese oxides are prominent candidates for the catalytic oxidation of volatile organic compounds (VOCs) or ambient decomposition of O3 individually. Here, we compared various preparation methods to create a defect-enriched Ag-MnOx nanocomposite that exhibits a remarkably multifunctional activity in VOC combustion and ozone decomposition. Ag+ ions were well-dispersed in the microtunnels of Ag-MnOx-H via hydrothermal replacement of the original K+ ions; this catalyst's benzene combustion efficiency (T90% = 216 °C at a space velocity of 90 000 mL h-1 g-1) was comparable to that of typical noble metal catalysts. Moreover, the decomposition of ozone over the Ag-MnOx-H catalyst (space velocity = 840 000 mL h-1 g-1) under a relative humidity of 60% was above 90%, indicating that it is a promising material for ozone elimination in practical application. The local structure results indicated that silver incorporation via the hydrothermal method facilitates the formation of nonstoichiometric defects in the MnOx matrix. The large number of active oxygen species related to O vacancies appeared to play critical roles in VOC combustion; moreover, the oxygen vacancies originating from O defects were also critical in O3 abatement. This work provides multifunctional catalysts for VOC combustion and ambient O3 decomposition and may assist with the rational design of MnOx catalysts for application in various conditions.