Colloidal Au and Au-alloy catalysts for direct borohydride fuel cells: Electrocatalysis and fuel cell performance

Supported colloidal Au and Au-alloys (Au-Pt and Au-Pd, 1:1 atomic ratio) on Vulcan XC-72 (with 20 wt% metal load) were prepared by the Bönneman method. The electrocatalytic activity of the colloidal metals with respect to borohydride electro-oxidation for fuel cell applications was investigated by voltammetry on static and rotating electrodes, chronoamperometry, chronopotentiometry and fuel cell experiments. The fundamental electrochemical techniques showed that alloying Au, a metal that leads to the maximum eight-electron oxidation of BH4−, with Pd or Pt, well-known catalysts of dehydrogenation reactions, improved the electrode kinetics of BH4− oxidation. Fuel cell experiments corroborated the kinetic studies. Using 5 mg cm−2 colloidal metal load on the anode, it was found that Au-Pt was the most active catalyst giving a cell voltage of 0.47 V at 100 mA cm−2 and 333 K, while under identical conditions the cell voltage using colloidal Au was 0.17 V.