ELECTROCHEMICAL METALLIZATION OF CARBON ELECTRODES

A series of transition metals was electrodeposited on glassy carbon el ectrodes using cyclic voltammetry. The resultant chemically modified e lectrodes were amperometrically tested for catalytic activity towards the oxidation and reduction of hydrogen peroxide (H2O2). Their behavio ur was characterised by plotting current response to H2O2 versus the a pplied potential. An unusual property found in the case of both ruthen ium and rhodium was their capacity to reduce hydrogen peroxide at posi tive potentials. This leads to the possibility of measuring large redu ction currents at low positive potentials. Other electroactive species were shown to give low responses at these potentials. The main proble m encountered with such metallised electrodes is the lack of stability of their catalytic properties. The modified electrode with the greate st stability was found to be a codeposited ruthenium and rhodium surfa ce. After an initial drop-off in response, the electrodes remained sta ble for over two months. Twenty replicate injections gave a response o f 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 d etection was determined to be 5 x 10(-8) M hydrogen peroxide. (C) 1998 Elsevier Science B.V. All rights reserved.