Analysis of the kinetics of borohydride oxidation in Cu anode for direct borohydride fuel cell

A multi-step mechanism is discussed for the oxidation of BH4- on Cu anode in NaOH solution. Polarization experiments are conducted in 2 M sodium hydroxide solutions with 0.5, 1.0, and 2.0 M NaBH4 at 25, 50, and 75 degrees C, respectively. The rate-determining step is the electrochemical oxidation of BH4,ad- that reacted with OHad- at low overpotentials and changes to the competitive adsorption of BH4- or OH- at higher overpotentials. The theoretical predictions are satisfactorily in accordance with the polarization data. However, these predictions deviate from the data at the highest temperature or concentration of BH4- because of the bubbling of the side product, H-2. (C) 2012 Elsevier B.V. All rights reserved.