Mixed Cu-Au catalysts are prepared on electrochemically activated polyacrylonitrile (PAN)-based carbon fibre supports. The preparation is achieved through cation-exchange of Cu2+-ions on electro-oxidized carbon fibres, cathodic reduction of the exchanged Cu2+ to Cu and subsequent immersion of the carbon-Cu systems in solutions of Au-salts for various time periods, in order to obtain different coverages of Au on the electrodes. Mixed Au-Cu systems are also prepared through Au3+ exchange, reduction of Au3+ to Au and subsequent Cu2+-exchange and reduction to Cu. The electrocatalytic efficiency of the produced systems is investigated in the electrochemical oxidation of formic acid and hydrazine. The best results are obtained after immersion of the carbon-Cu systems in a AuCl3 solution for 30s. The study was carried out by cyclic voltammetric and impedance spectroscopic measurements.?