Electrochemical metallisation of carbon electrodes

A series of transition metals was electrodeposited on glassy carbon electrodes using cyclic voltammetry. The resultant chemically modified electrodes were amperometrically tested for catalytic activity towards the oxidation and reduction of hydrogen peroxide (H2O2). Their behaviour was characterised by plotting current response to H2O2 versus the applied potential. An unusual property found in the case of both ruthenium and rhodium was their capacity to reduce hydrogen peroxide at positive potentials. This leads to the possibility of measuring large reduction currents at low positive potentials. Other electroactive species were shown to give low responses at these potentials. The main problem encountered with such metallised electrodes is the lack of stability of their catalytic properties. The modified electrode with the greatest stability was found to be a codeposited ruthenium and rhodium surface. After an initial drop-off in response, the electrodes remained stable for over two months. Twenty replicate injections gave a response of 0.63 mu A to 1 mM H2O2 at an applied voltage of 67 mV versus Ag/AgCl and the relative standard deviation was 0.78%. The 3 sigma limit of detection was determined to be 5 x 10(-8) M hydrogen peroxide. (C) 1998 Elsevier Science B.V. All rights reserved.