Influence of thermal treatments on the stability of Pd nanoparticles supported on graphitised ordered mesoporous carbons

The graphitisation of ordered mesoporous carbons (CMK-3) was carried out by thermal treatments under different conditions of temperature and heating rate. The electrochemical characterization in acidic medium of the graphitised CMK-3 showed that such a thermal treatment is effective to decrease the carbon oxidation rate (corrosion) while preserving a good porosity in terms of capacitance. Besides, the graphitisation degree and, in consequence, the electrochemical corrosion resistance can be modulated by an appropriate choice of thermal treatment conditions, where the heating rate and temperature appear as critical parameters. Under certain graphitisation conditions, the carbon corrosion of CMK-3 can be minimized showing lower rates compared to a commercial carbon black (Vulcan). Palladium nanoparticles were supported on the most promising graphitised CMK-3 and Vulcan using a method based on impregnation and reduction with borohydride, resulting in suitable metal crystallite sizes. The electrocatalytic activity towards the oxidation of carbon monoxide and formic acid were assessed in aqueous sulphuric acid electrolyte for application at the anode of direct formic acid fuel cells (DFAFCs). The best activity results were obtained for the Pd catalyst supported on a graphitised CMK-3.