The influence of different co-catalysts in Pt-based ternary and quaternary electro-catalysts on the electro-oxidation of methanol and ethanol in acid media

One of the key objectives in fuel cell technology is to reduce Pt loading by the improvement of its catalytic activity towards alcohol oxidation. Here, a sol–gel based method was used to prepare ternary and quaternary carbon supported nanoparticles by combining PtRu with Mo, Ta, Pb, Rh or Ir, which were used as electro-catalysts for the methanol and ethanol oxidation reactions in acid medium. Structural characterization performed by XRD measurements revealed that crystalline structures with crystallites ranging from 2.8 to 4.1 nm in size and with different alloy degrees were produced. Tantalum and lead deposited as a heterogeneous mixture of oxides with different valences resulting in materials with complex structures. The catalysts activities were evaluated by cyclic voltammetry and by Tafel plots and the results showed that the activity towards methanol oxidation was highly dependent of the alloy degree, while for ethanol the presence of a metal capable to promote the break of CC bond, such as Rh, was necessary for a good performance. Additionally, the catalysts containing of TaOx or PbOx resulted in the best materials due to different effects: the bi-functional mechanism promoted by TaOx and a better dispersion of the catalysts constituents promoted by PbOx.

► Crystalline structures with different alloy degrees prepared by sol–gel method.
► Ta and Pb produced complex structures of mixtures of oxides with different valences.
► Activity towards methanol oxidation was highly dependent of the alloy degree.
► Ethanol oxidation needed the presence of a metal capable to promote the break of CC bond.
► Catalysts containing of TaOx or PbOx resulted in the best catalytic materials.