Synergistic effect of CuO nanocrystals and Cu-oxo-Fe clusters on silica support in promotion of total catalytic oxidation of toluene as a model volatile organic air pollutant

Abstract

Monometallic (CuO and FeOx) and bimetallic (CuFeOx) entities on different supports are promising transition-metal low-cost catalysts for catalytic oxidation of volatile organic compounds (VOC) from industrial air alternatively to noble-metal catalysts which are currently in use. In this work we report for the first time that the promotion of catalytic oxidation of toluene as a model VOC is due to the cooperative redox effect between CuO nanocrystals and finely dispersed Cu-oxo-Fe clusters on mesoporous silica with defined Fe/Cu molar ratio. This increases the number and reactivity of adsorbed electrophilic (O− and O2−) as well as nucleophilic lattice oxygen (O2-) species at the CuO crystal and and Cu-oxo-Fe cluster interface, thus providing up to twofold enhancement in catalytic activity for total oxidation of toluene. Catalysts were prepared via direct synthesis of Fe-functionalized disordered mesoporous silica containing only isolated iron sites followed by copper addition via impregnation.