Effect of silver nanoparticles deposited on micro/mesoporous activated carbons on retention of NOx at room temperature

Wood-based activated carbon was modified by deposition of silver using Tollens method. Adsorbents with various contents of silver were used to study NO2 and NO (the product of NO2 reduction by carbon) retention. The surface of the initial and exhausted materials was characterized using adsorption of nitrogen, XRD, SEM/EDX, FTIR and TA. The results indicated that with an increasing content of silver on the surface the capacities to retain NO2 and NO increase until the plateau is reached. The performance depends on the dispersion of nanoparticles and their chemistry. Highly dispersed small silver metal particles promote formation of chelates with NO2 and/or with NO. An excess of Tollens reagent results in formation of larger silver crystals and silver oxide nanoparticles. If sufficiently dispersed, they also enhance the retention of NO2 via formation of nitrates deposited in the pore system. The surface of the carbon matrix is also active in NO2 retention, providing the small pores and edges of graphene layers, where the reductions of NO2/oxidation of carbon take place.

Silver nanoparticles deposited on the surface of activated carbons using Tollens method significantly increase the ability of the carbons for NO2 and NO retention.Figure optionsDownload high-quality image (96 K)Download as PowerPoint slideResearch highlights
► Introduction of silver nanoparticles, using Tollens method, significantly increases the performance of carbons as adsorbents NO2 and NO.
► The retention of NO2/NO depends on the dispersion of silver nanoparticles and their chemistry.
► Highly dispersed small silver metal particles promote the formation of complexes either with NO2 or NO. Such efficiently used catalysts are produced only when the amount of silver matches the amount of aldehyde groups and/or incompletely oxidized functionalities, which are involved in deposition of those silver nanoparticles.