GROWING SMALL METAL-PARTICLE AS REDOX CATALYST

It is now well established that the redox property of small metal part icles differs from their bulk value and depends on the size of the par ticle, This size dependent-redox property has a strong influence on th e chemical reactivity of the metal. Our experiment shows that the cata lytic property of commonly-used transition metals such as Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Pt, Au and Hg is also influenced by this size-depe ndent redox property. We have studied the redox catalytic property of growing small particles which are formed as transient intermediates du ring the reduction of the corresponding metal salts in water, The grow ing small particles act as electron relay systems between the oxidant and reductant and thus catalyse the redox reactions which are kinetica lly inert. In many cases the corresponding larger and stable metal sol s behave either as a weaker catalyst or catalytic activity becomes red undant. Catalytic activity of small particles originates from their lo wer reduction potential compared to the bulk value.