Study of the Electrochemical Activities of Mo-Modified Pt Catalysts, for Application as Anodes in Direct Methanol Fuel Cells: Effect of the Aggregation Route

Abstract

Electrocatalysts with constant metallic composition, consisting of carbon-supported platinum and molybdenum phases, were synthesized following the thermolysis (thr) and borohydride (bhr) reduction methods and using different metallic precursors. The obtained electrocatalysts were characterized by X-ray energy-dispersive spectrometry, X-ray diffraction and high resolution transmission electron microscopy. Their activities were studied by cyclic voltammetry. Different surface structures were obtained and the electrochemical activities toward methanol oxidation were compared. Pt, MoO2 and MoO3 phases were well identified with the characterization techniques used. However, the electrochemical responses obtained from both sample series were considerably different, suggesting that the arrangement and relationships between active phases strongly depend on the synthesis method and aggregation sequence of the metallic precursors, and being the cause of different catalytic activities and stabilities of molybdenum oxide phases. The bhr method offered higher activity than the thr method. Among the sample series obtained by bhr method, the catalyst obtained by platinum deposition on the previously synthesized molybdenum on carbon, led to the highest overall activity.