Chronopotentiometric Investigation of Borohydride Oxidation at a Gold Electrode

Sodium borohydride presents interesting options for electrochemical power generation acting either as a hydrogen source or an anodic fuel for direct borohydride fuel cells. Though there have been several papers concerning electrochemical determination of relevant thermodynamic and kinetic parameters to the borohydride system, there are many basic aspects that have not yet been systematically studied. This paper reports chronopotentiometric studies of the electro-oxidation of at a gold electrode in 2 M NaOH solutions at temperatures ranging from 25 to . Gold displays a rather good oxidation activity, and the overall oxidation process is shown to be irreversible involving a number of exchanged electrons close to the theoretically expected value of 8. For the specific potential and concentration ranges observed, the results suggest that the rate-determining step is an irreversible, diffusion-controlled, one-electron oxidation step for which several key kinetic parameters (α, , and ) are calculated.