Sol-gel-entrapped nano silver catalysts-correlation between active silver species and catalytic behavior

Vasile I. Pârvulescu, Bogdan Cojocaru, Viorica Pârvulescu, Ryan Richards, Zhi Li, Chris Cadigan, Pascal Granger, Pierre Miquel, Chris Hardacre

    Research output: Contribution to journalArticlepeer-review


    Silver colloids prepared by reducing AgNO3 in aqueous solution with sodium citrate were embedded in alumina following two different preparation procedures resulting in samples containing 3 and 5 wt.% silver. Characterization of these materials using TEM, XPS, XAES, CP/MAS NMR, XRD, and adsorption-desorption isotherms of nitrogen showed that embedding the pre-prepared silver colloids into the alumina via the sol-gel procedure preserved the particle size of silver. However, as XAES demonstrates, the catalysts prepared in a sol-gel with a lower amount of water led to embedded colloids with a higher population of Ag+ species. The catalytic behaviors of the resultant catalysts were well correlated with the concentration of these species. Thus, the active silver species of the catalysts containing more Ag+ species selectively converts NO to N2. However, subsequent thermal aging leads to an enhancement of the conversion of NO parallel to slight alteration of the selectivity with the appearance of low amounts of N2O despite an increase of Ag+ species. Accordingly, an optimal surface Ag0/Ag+ ratio is probably needed, independently of the size of silver particles. It was found that this optimal ratio strongly depends on the operating conditions during the synthesis route.

    Original languageEnglish
    Pages (from-to)92-100
    Number of pages9
    JournalJournal of Catalysis
    Issue number1
    Publication statusPublished - 25 May 2010


    • NO reduction with hydrogen and CO
    • Silver colloids
    • Sol-gel synthesis


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