Synthesis of nanostructured carbon on graphite electrodes with a supported Co catalyst for preparing anodes for microbial fuel cells

Resumo

The synthesis of nanostructured carbon (NSC) on graphite electrodes with a supported Co catalyst by C₃ and C₄ alkane pyrolysis in the presence of hydrogen has been investigated. Co(II) hydroxo compounds have been deposited onto graphite, and a Co/graphite catalyst has been prepared by the homogeneous precipitation of divalent cobalt from cobalt nitrate solutions in the presence of urea and compounds containing OH groups, namely, lower alcohols (ethanol, n-propanol, and n-butanol) and polyols (ethylene glycol, glycerol, and sorbitol). The effect of Co catalyst preparation conditions on the pyrolytic activity of the catalyst and on the morphology of the synthesized NSC has been investigated. An active Co/graphite catalyst forms in the presence of an alcohol containing 1-3 OH groups. A fairly uniform NSC layer on the graphite surface is obtained at Co(II) nitrate concentrations of 0.05–0.1 mol/L, a urea concentration of 1 mol/L, and glycerol concentrations of 5–20 vol %. The electrochemical characteristics of the electrodes prepared and those of a microbial fuel cell (MFC) involving an NSC/graphite anode and an activated-sludge microbial consortium have been determined. The maximum power of the MFC under the conditions examined is 4.8 mW per square meter of the anode’s geometric surface area.