Boosting the catalytic activity of magnetite in soot oxidation by surface alkali promotion

TheeffectofalkalipromotionofaFe 3 O 4 catalystinsootcombustionwassystematicallyinvestigatedforaseriesof alkalielements(Li,Na,K and Cs)atvarioussurface coverages. The correlation between catalyst performance and work function lowering was established and discussed in terms of the electron donor character of the alkali promotion. This effect was found to follow the sequenc e of the increasing ionic radii of the alkali promoters Li b Na b K b Cs. For each alkali promoter, the highest activ ity corresponds to a different optimal surface coverage.