Electrochemically reductive dechlorination of micro amounts of 2,4,6-trichlorophenol in aqueous medium on molybdenum oxide containing supported palladium

An electrodepositing method is used to prepare a Pd/MoOx/GC (glass carbon) composite electrode that provides a surface modification with catalytic properties for reductive dechlorination of 2,4,6-trichlorophenol in aqueous medium at ambient temperature. The palladium particles are uniformly dispersed on a MoOx film that is previously electrodeposited on a GC electrode. XPS (X-ray photoelectron spectroscopy) of this composite electrode presents a broad peak in the Mo (3d) region revealing the existence of Mo6+ species as well as lower valence states such as Mo5+, Mo4+. Compared with the Pd/GC electrode surface, the Pd (3d) region reveals another peak whose binding energy value is higher than in Pd/GC. This peak suggests a strong interaction between the palladium particles and the MoOx film. This composite electrode shows better performance for electrocatalytic reductive dechlorination of 2,4,6-trichlorophenol than Pd/GC. Totally dechlorinated product (phenol) is observed at the early stage of electrolysis, no intermediate products are observed besides trace amounts of 2,4-dichlorophenol. The formation of trace amounts 2,4-dichlorophenol may occur by direct electronation on the cathode. The influence of current density and substrate concentration are also investigated. (C) 2004 Elsevier Ltd. All rights reserved.