Ethylene glycol electrooxidation in alkaline medium at multi-metallic Pt based catalysts

The electrooxidation of ethylene glycol at nanostructured platinum based catalysts was studied in alkaline medium. The optimum metals loading and atomic composition for ethylene glycol electrooxidation were determined. The addition of Bi to platinum leads to decrease the onset potential of EG electrooxidation of about 70 mV and to achieve higher current densities in the whole studied potential range. The ternary catalyst PtPdBi/C does not change the onset potential of EG oxidation, but leads to increase the current densities compared to PtBi catalysts. The EG electrooxidation enhancement with binary and ternary catalysts was confirmed in SAMFC (solid alkaline membrane fuel cell) experiments, the open circuit voltage (ocv) increasing from 0.66 to 0.83 and 0.81 V and the maximum achieved power density raising from 19 to 22 and 28 mW cm−2 with Pt, PtBi and PtPdBi catalysts, respectively. An attempt to explain the change in catalytic behavior was made by analysis of SAMFC reaction products in the anode outlet and by in situ FTIR spectroscopy measurements. It was shown that the addition of foreign atoms to platinum led to decrease the ability of the catalyst to break the C–C bond, likely due to dilution of surface platinum atoms. But, in the same time, catalyst containing Pd and Bi seems to activate the oxidation of EG in oxalate compared to pure platinum. The role of Bi and Pd was discussed. It was proposed that Bi mainly favors the adsorption of OH species but also affects the product distribution by changing the composition of chemisorbed species, whereas Pd only limits the poisoning of Pt sites by changing the composition of chemisorbed species.