Tuning the Microstructures of ZnO To Enhance Photocatalytic NO Removal Performances

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Controlling dilute nitrogen oxides (NO) pollution, especially at parts per billion (ppb) levels, remains a significant environmental challenge.
• Existing methods often struggle with complete NO removal or inadvertently produce secondary pollutants like nitrogen dioxide (NO2).
• Photocatalysis offers a promising route for NO abatement, but requires optimized materials for efficient adsorption, activation, and removal.

Purpose of the Study:

• To investigate the microstructure regulation of zinc oxide (ZnO) photocatalysts for effective dilute NO removal.
• To explore the synthesis of ZnO with diverse morphologies and defect characteristics using an ionic liquid-based solid-state method.
• To elucidate the mechanisms behind enhanced NO removal and suppressed NO2 formation in tailored ZnO photocatalysts.

Main Methods:

• Synthesized ZnO photocatalysts by adjusting reaction temperature and alkalinity in an ionic liquid-based solid-state process.
• Characterized the microstructures, morphologies, optical properties, and defect states (e.g., Vo″ defects) of the synthesized ZnO.
• Evaluated the photocatalytic performance of the tailored ZnO for dilute NO removal under light irradiation, quantifying NO removal efficiency and NO2 yield.

Main Results:

• The synthesized ZnO photocatalysts exhibited unique nucleation, diverse morphologies (nanoparticles, nanorods), and defect-related optical properties.
• Tailored ZnO demonstrated significantly enhanced NO removal (4.16-fold increase) and drastically reduced NO2 formation (2.76 orders of magnitude decrease).
• Defect-related surface-interface aspects, particularly Vo″ defects, were crucial for the improved photocatalytic activity and selectivity.

Conclusions:

• Facile regulation of ZnO microstructures via ionic liquid-based synthesis is effective for developing advanced photocatalysts.
• Optimized ZnO microstructures and defect engineering enhance charge carrier separation and surface interactions, boosting active species production.
• This approach provides a viable strategy for efficient and selective removal of ppb-level NO pollution, avoiding secondary NO2 emission.