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

H2O is often critical in determining the activity and stability of metal oxide catalysts for HCHO oxidation; however, synthesis of metal oxide catalysts with super resistance to H2O remains a challenging. Herein, we synthesized Akhtenskite-type MnO2 catalyst with Mn-O-Mn stretching along MnO6 octahedra layers, which promotes the utilization of the associatively adsorbed H2O. The activity and stability of formaldehyde oxidation at room temperature enhanced in humid air. Diffuse-reflectance infrared Fourier transform (DRIRFT) spectroscopy was used to characterize the H2O adsorption and intermediate species. The associatively adsorbed H2O promotes the oxidation of formaldehyde to CO2 via the formic acid intermediate. The service life of MnO2 is prolonged due to formic acid generation. MnO2 gradually deactivates when formic acid accumulates and forms formate and hydrogen carbonate species. This study provides significant insights into the development of a high-efficiency MnO2 catalyst for formaldehyde oxidation in humid air, and the developed MnO2 catalyst is a promising candidate for application in practical formaldehyde elimination.