Improvements in direct borohydride fuel cells using three-dimensional electrodes

The oxidation of borohydride ions on three-dimensional electrodes such as vitreous carbon (RVC) coated with gold nanoparticles and silver porous sponge material was investigated. The RVC electrodes were covered with gold using PVD sputtering for different times of exposure. The open pore silver sponge electrode was prepared by the calcination of dextran or starch polymers, used as a framework, and silver nitrate mixtures between 400 and 600 °C. The porous silver was characterised by Scanning Electron Microscopy (SEM) and showed pore sizes between 1 and 20 μm. The activity of these electrodes as anode catalysts for the direct oxidation of borohydride was evaluated by cyclic voltammetry in 0.02 mol dm−3 NaBH4 plus 3 mol dm−3 NaOH. The number electrons, the charge transfer coefficient and the homogeneous and kinetic rate constants were calculated and the values are comparable with those reported in the literature.