Regulation of mixed Ag valence state by non-thermal plasma for complete oxidation of formaldehyde

Formaldehyde is an important air pollutant and its removal is essential to protect human health and meet environmental regulations. Ag-based catalyst has a considerable potential for HCHO oxidation in low temperature range. The valence state of Ag is one of the key roles in formaldehyde catalytic oxidation. However, its effect on activity is still ambiguous. Non-thermal plasma and conventional calcination were employed to regulate Ag valence state in this study. Three Ag-Co/CeO2 catalysts with totally different distribution of Ag species were obtained. A special mixed Ag valence state, similar to 50% Ag delta+ with a few Ag-0 and Ag+, was achieved by plasma activation. It had the merits of both good activity and stability. A close relationship between Ag valence state and the activity for HCHO oxidation was established. The activity of different Ag species follows the order: Ag delta+ + Ag-0 + Ag+ > Ag delta+ > Ag-0 > Ag+. (C) 2021 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

The valence state of silver plays a crucial role in the catalytic oxidation of formaldehyde. By employing non-thermal plasma and conventional calcination methods, researchers were able to regulate the valence state of silver and obtain a special mixed valence state with good activity and stability for the oxidation of formaldehyde.