Pt/C, Au/C and Pd/C Catalysts for Alkaline-based Direct Glycerol Fuel Cells

Abstract

This study presents the results of the preparation of monometallic catalysts for glycerol electroxidation by simple chemical reduction methods: formic acid for Pt, citrate-assisted NaBH4 for Au and ammonia- assisted NaBH4 for Pd. The metal nanoparticles, within a range of 3-7 nm, anchor successfully, as demonstrated by termogravimmetry and EDS analyses, and spread, as displays by the TEM images, on the carbon support. The XRD patterns display the fcc crystalline facets, except for the case of Pd/C, where peaks associated to the formation of metastable palladium carbide are present. The electrochemical activity for glycerol oxidation was evaluated in a three electrode glass cell by cyclic voltammetry, revealing that Pt/C possesses the lowest onset potential and Au/C the maximum current density. The Pd/C catalysts also present a electrochemical activity (despite the presence of PdC), with an intermediate onset potential between Au and Pt. Regarding the influence of the metal loading, Pt/C displays the best performance for the high metal loaded 60% Pt/C, whereas for Au/C and Pd/C, lowest loaded 20% Au/C and Pd/C. The direct comparison of these three materials in a chronoamperometric measurement (at -0.2 V vs Hg/HgO) reveals that Pt/C is the most effective material at such more useful potentials. Finally, the product distribution reveals that the metal may be a useful tool for a pre-selection of a particular product.