Electrocatalysis of borohydride oxidation on colloidal Pt and Pt-alloys (Pt- Ir, Pt-Ni, and Pt-Au) and application for direct borohydride fuel cell anodes

Colloidal Pt and Pt-alloys (Pt-Au, Pt-Ni, and Pt-Ir, 1:1 atomic ratio) supported on Vulcan XC-72 (20% wt metal load) were prepared according to the Bonneman method and investigated for electrocatalytic activity with respect to borohydride oxidation for fuel cell applications. Voltammetry on static and rotating electrodes, chronopotentiometry, and chronoamperometry were performed on the colloidal catalysts immobilized on glassy carbon with the help of Nafion 117. The BH4- electro-oxidation mechanism is complex and it could involve, depending on the catalyst, a number of species such as BH4- directly, BH3OH-, and H-2 (the latter two species formed in catalytic hydrolysis). Direct borohydride fuel cell experiments using a 2 M NaOH-2 M NaBH4 solution on the anode side, 5 mg cm(-2) colloidal anode catalyst load, Nafion 117 membrane, and an O-2 gas diffusion cathode with 4 mg cm(-2) Pt, showed that Pt-Ir and Pt-Ni were the most active anode catalysts, giving a cell voltage of 0.53 V at 100 mA cm(-2) and 333 K. (c) 2005 The Electrochemical Society.