Catalytic oxidation of dichloromethane over Pt-Co/HZSM-5 catalyst: Synergistic effect of single-atom Pt, Co3O4, and HZSM-5

The catalytic degradation of chlorinated volatile organic compounds (CVOCs) at low temperatures is a great challenge. In this work, Pt-Co/HZSM-5 ternary catalysts were synthesized and used for the catalytic oxidation of dichloromethane (DCM). By adding only trace amounts of Pt (0.01 wt. %), Pt-Co/HZSM-5 ternary catalyst exhibits better CO2 yield and lower by-product yield than Co/HZSM-5 catalyst. Besides, it maintained stable activity for at least 45 h without substantial changes. The addition of water vapor to the DCM degradation process on Pt-Co/HZSM-5 ternary catalysts was shown to promote DCM conversion, CO2 yield, and HCl yield. Catalyst characterization shows that Co (in the form of Co3O4) could effectively anchor Pt atoms, thus realizing the single-atom dispersion of Pt. In turn, the formed single-atom Pt increases the proportion of oxygen vacancies on the surface of Co3O4, thereby enhancing the redox properties of Co3O4. In the catalytic oxidation process, DCM first adsorbed and dechlorinated on the surface of HZSM-5 due to abundant acid sites and then completely dissociated under the interaction of Pt and Co. Thanks to the synergies of Pt, Co, and HZSM-5, Pt-Co/HZSM-5 exhibited appropriate redox ability, a suitable distribution of acid sites, and sufficient surface adsorbed oxygen, possibly explaining its lower by-product yields and the more efficient formation and desorption of HCl.