Remarkable MnO₂ structure-dependent H₂O promoting effect in HCHO oxidation at room temperature

Area of Science:

• Catalysis
• Materials Science
• Environmental Chemistry

Background:

• Water is crucial for metal oxide catalyst performance in formaldehyde oxidation.
• Developing water-resistant catalysts for efficient formaldehyde oxidation remains a challenge.

Purpose of the Study:

• To synthesize a novel Akhtenskite-type MnO2 catalyst with enhanced water resistance.
• To investigate the role of adsorbed water in formaldehyde oxidation over MnO2 catalysts.
• To understand the deactivation mechanism of MnO2 catalysts in humid conditions.

Main Methods:

• Synthesis of Akhtenskite-type MnO2.
• Formaldehyde oxidation activity and stability tests at room temperature in humid air.
• Diffuse-reflectance infrared Fourier transform (DRIRFT) spectroscopy for characterizing adsorbed water and intermediates.

Main Results:

• The Akhtenskite-type MnO2 catalyst demonstrated enhanced activity and stability for formaldehyde oxidation in humid air.
• Associatively adsorbed water was found to promote formaldehyde oxidation via a formic acid intermediate.
• Catalyst deactivation was linked to the accumulation of formic acid, leading to formate and hydrogen carbonate species.

Conclusions:

• The Akhtenskite-type MnO2 catalyst effectively utilizes adsorbed water for efficient formaldehyde oxidation.
• Understanding water's role and deactivation pathways is key for designing robust catalysts.
• This MnO2 catalyst shows potential for practical applications in formaldehyde removal from air.