Design of Bifunctional Cu-SSZ-13@Mn₂Cu₁Al₁O_<i>x</i> Core–Shell Catalyst with Superior Activity for the Simultaneous Removal of VOCs and NO_<i>x</i>

Abstract

Synchronous control of volatile organic compounds (VOCs) and nitrogen oxides (NO_<i>x</i>) is of great importance for ozone and PM_2.5 pollution control. Balancing VOC oxidation and the NH₃-SCR reaction is the key to achieving the simultaneous removal of these two pollutants. In this work, a vertically oriented Mn₂Cu₁Al₁O_<i>x</i> nanosheet is grown <i>in situ</i> on the surface of Cu-SSZ-13 to synthesize a core-shell bifunctional catalyst (Cu-SSZ-13@Mn₂Cu₁Al₁O_<i>x</i>) with multiple active sites. The optimized Cu-SSZ-13@Mn₂Cu₁Al₁O_<i>x</i> catalyst delivered excellent performance for the simultaneous removal of VOCs and NO_<i>x</i> with both 100% conversion at 300 °C in the presence of 5% water vapor. Physicochemical characterization and density functional theory (DFT) calculations revealed that Cu-SSZ-13@Mn₂Cu₁Al₁O_<i>x</i> possesses more surface acidity and oxygen vacancies. The charge transfer between the core and shell is the intrinsic reason for the improved activity for both VOC and NO_<i>x</i> removal. The molecular orbital theory is used to explain the different adsorption energies due to the different bonding modes between the core-shell and mixed individual catalysts. This work provides a novel strategy for designing efficient catalysts for the simultaneous removal of VOCs and NO_<i>x</i> or other multiple pollutants.