Hydrophobic Mn/ZSM-5 modification for highly efficient O₃ decomposition under humidity conditions

Area of Science:

• Materials Science
• Catalysis
• Environmental Chemistry

Background:

• Ozone (O3) decomposition catalysts deactivate due to water adsorption in humid environments.
• Developing robust catalysts for O3 removal under high relative humidity (RH) is critical.

Purpose of the Study:

• To enhance the moisture resistance and catalytic activity of Mn/ZSM-5 for O3 decomposition.
• To investigate the structure-activity relationship of modified Mn/ZSM-5 catalysts.

Main Methods:

• Synthesis of x-Mn/ZSM-5 catalysts via organic functionalization with alkylsilanes.
• Characterization using techniques like BET, XRD, TEM, XPS, and H2-TPR.
• Ozone conversion measurements under varying humidity levels.
• Density Functional Theory (DFT) calculations.

Main Results:

• The C4-Mn/ZSM-5 catalyst exhibited excellent O3 conversion (>85% for 6h at 80% RH).
• Organic functionalization created siloxane bonds, increasing surface hydrophobicity and modulating MnOx species.
• Modified catalysts showed increased low-valence Mn species and oxygen vacancies (Vo).
• DFT calculations identified MnOH sites and Vo as active centers, with MnOH being more efficient.

Conclusions:

• The C4-Mn/ZSM-5 catalyst demonstrates superior moisture resistance and O3 decomposition activity.
• Hydrophobicity enhancement and the synergistic effect of MnOH sites and oxygen vacancies are key to performance in high RH.
• This work provides a strategy for designing stable O3 decomposition catalysts for practical applications.