Metal-support interaction enhanced silver-based catalysts on oxygen-vacancy modified commercial support for low-temperature trace formaldehyde removal

Background Low-temperature catalytic oxidation of trace formaldehyde using silver-based catalysts is of significant research interest for indoor-air quality control, due to their low cost and high catalytic performance. Methods A silver-based catalyst (K-Ag/La-CeO 2 /Al 2 O 3 ), comprising Ag and K supported on La-CeO 2 modified commercial Al 2 O 3 carrier, was developed based on metal-support interactions and oxygen vacancies (O v ) principles. Its mechanism was examined systematically through carefully designed reduction experiments combined with comprehensive catalysis characterizations. Significant findings The catalyst required no hydrogen reduction prior to use and completely oxidized formaldehyde at 90°C. The active sites and reaction pathway were systematically elucidated. Abundant surface hydroxyl groups were present and actively participated in formaldehyde oxidation. Metal-support interactions between Ag and the O v -enriched surface facilitated the formation of positively charged silver clusters ( A g + n ), which oxidized formaldehyde more readily than metallic Ag at low temperatures. Ag + can be formed counterintuitively during A g + n reduction. The presence of key intermediates of dioxymethylene (DOM), formate, and CO established the reaction pathway as HCHO →DOM →HCOO* →CO →CO 2 , where formate formation was the rate-limiting step. This work provides a new strategy to boost the performance of Ag-based catalysts in the oxidation of formaldehyde and other volatile organic compounds.