On electrocatalysis in alkene–molybdenum(VI) system at Pt/acidic solution interface

Abstract

The catalytic reduction of ethene, propene and 1butene on a polycrystalline Pt electrode in strongly acidic medium containing Mo(VI) oxo-species has been examined by cyclic voltammetry taking into account the influence of perchloric acid and molybdate concentration as well as that of the scan rate on the cathodic current response. About tenfold increase in the reaction rate of each alkene investigated has been achieved at the optimum molybdate concentration of 1-2.5 mM in 4-M HClO 4 solution as a supporting electrolyte in comparison with that obtained in the absence of Mo(VI) oxo-species. It was ascertained that the catalytic reduction current strongly depends on the amount of cationic Mo(VI) oxo-species at the Pt electrode/solution interface. Simultaneously, the electroreduction of cationic Mo(VI) oxo-species was found to be effectively enhanced in the presence of alkene. According to the proposed reaction pathways, alkenes are reduced to alkanes via a nonfaradaic reaction with Mo(V) and/or Mo(III) cationic moieties formed in the preceding reductive electron-transfer steps from the parent cationic Mo(VI) oxo-species. Continuous regeneration of the electroactive Mo(VI) and/or Mo(V) cationic oxo-species accounts for the observed catalytic phenomenon.