Effect of the Oxidation Potential of the Metal Deposit on the Photocatalytic Activity of Metallized Titanium Dioxide Samples

Abstract

A commercial anatase pigment was coated with copper, silver, palladium, platinum and gold, respectively. That means the oxidation potential of the deposit was varied from about +0.3 V (vs. NHE) to about +1.5 V (vs. NHE). The photocatalytic activity of the metallized titanium dioxide samples was evaluated using the degradation of methyl orange as a test reaction. In comparison to the neat titanium dioxide the metallized samples exhibit enhanced photocatalytic activity. A longer lifetime of charge carriers in the surface region of the metallized samples is the reason for their better activity, as photo-EMF investigations reveal.The photocatalytic activity of the metallized samples, however, depends on the kind of metal used although the amount of metal on the titanium dioxide was the same and the particle sizes of the deposits were similar for all samples. This finding shows that the oxidation potential of the metal deposit plays a major role for the photocatalytic activity of the support material because it governs the depth of the electron traps.The best photocatalytic activity was observed for titanium dioxide coated with silver. That means under the conditions used an oxidation potential of +0.8 V (vs. NHE) of the deposit is most suitable for the photocatalytic activity of titanium dioxide.