The effect of surfactants on the kinetics of borohydride oxidation and hydrolysis in the DBFC

• The borohydride oxidation rate can be increased or inhibited by surfactants.
• SDS surfactant below a 0.001 wt. % concentration, improves kinetics of borohydride oxidation.
• Triton X-100 and fluorocarbon surfactants decrease the oxidation current for borohydride ions.

The kinetics of borohydride oxidation at gold in the presence of surfactants was analysed by cyclic voltammetry at a static disc and linear sweep voltammetry at a rotating disc electrode. The electrolytes contained 0.02 mol dm−3 NaBH4 in 3 mol dm−3 NaOH, at 23 °C, in the absence and in the presence of surfactants including alkoxylated ether non-ionic Triton X-100, sodium dodecyl sulphate (SDS) and FC4430. A rotating disc gold electrode of 0.125 cm2 geometrical area was used. Through these techniques, the value of the diffusion coefficient of the borohydride ion was found to be 0.98 × 10−5 cm2 s−1 and (0.33–1.63) × 10−5 cm2 s−1 in the absence and in the presence of surfactants, respectively. The presence of Triton X-100, and FC4430 surfactants inhibited borohydride oxidation while SDS increased the current density at concentrations lower than 0.001 wt. %. As promising results were obtained in the presence of SDS, the kinetic parameters such as the heterogeneous rate constant (at various potentials), the standard rate constant and the charge transfer coefficient were calculated in the presence of this surfactant at different concentrations.