Enhanced formaldehyde oxidation on Pt/MnO₂ catalysts modified with alkali metal salts.

Novel Pt/MnO2 catalysts modified with alkali metal salts were prepared and exhibited excellent catalytic activity for formaldehyde oxidation. The effects of both cation and anion in the salts were investigated on the structure of catalysts and their catalytic activity. The Na(+) modification was demonstrated to be a facile and effective method to improve the catalysts performance for formaldehyde oxidation, but the anions remaining on the support might act as a mild poison by covering the surface active sites of manganese oxides. The enhancing effect of anions in the salts follows the order of CO3(2-)>SO4(2-)>NO3(-). A 100% formaldehyde conversion can be obtained at 50°C over the Na2CO3-modified catalyst. Further analyses indicate that strong metal-support interaction, well-dispersed Pt nanoparticles with small particle sizes and large surface area are important for high catalytic activity.