Efficient activation of Pd/CeO2 catalyst by non-thermal plasma for complete oxidation of indoor formaldehyde at room temperature

Abstract

Formaldehyde is a typical indoor air pollutant and its removal is essential to protect human health and meet environmental regulations. Efficient activation of Pd/CeO₂ catalyst by non-thermal plasma was investigated to achieve complete oxidation of formaldehyde at room temperature. The catalyst exhibited better activity and stability than conventional thermal reduced sample. Its HCHO conversion to CO₂ kept at over 80% during 300 min test at a gas hourly space velocity of 150, 000 mL/g/h and HCHO concentration of 100 ppm. While the conversion dropped from 70% to 50% within 300 min test for the sample reduced at 300 °C. Compared with thermal reduced catalyst, plasma reduced sample exhibited more abundant surface active oxygen species, smaller palladium particle size and narrower particle size distribution. Moreover, palladium particles were partial covered by ceria layer for thermal reduced sample. Although strong interaction between palladium and ceria could be formed, the loss of metallic palladium occurs and hence the oxygen activation and mobility abilities are blocked. In situ DRIFTs results suggested that the intermediates over Pd/CeO₂ catalyst were mainly formate, dioxymethylene and polyoxymethylene species, and the formate oxidation into CO₂ process was highly promoted in the presence of water.

Keywords: HCHO oxidation; Non-thermal plasma treatment; Pd/CeO(2); Room temperature.