Pd–Pt/Al 2O 3 bimetallic catalysts for the advanced oxidation of reactive dye solutions

Abstract

The Pd–Pt/Al 2O 3 bimetallic catalysts showed high activities toward the wet oxidation of the reactive dyes in the presence of 1% H 2 together with excess oxygen. Palladium was believed to act as a co-catalyst to spillover the adsorbed H 2 onto the surface of the oxidized Pt surface, and thereby the reducibility of the Pt increased greatly. The organic dye molecule adsorbed on the reduced Pt surface more easily than the oxidized Pt surface under the competition with excess oxygen, which is an essential step for the catalytic wet oxidation (CWO). The Pd–Pt/Al 2O 3 catalysts also produced H 2O 2 from H 2/O 2 mixture, and the hydroxyl radical was formed through the subsequent decomposition of H 2O 2. Additional oxidation of the reactive dyes was obtained with hydroxyl radical. The high activities of the Pd–Pt/Al 2O 3 catalysts were believed to be due to the combined effects of the faster redox cycle resulting from the increased reducibility of Pt surface and the additional oxidation of the reactive dyes with hydroxyl radical.