ELECTROCHEMICAL REDUCTION OF OXYGEN AT ELECTROCOATED NAFION-MODIFIED METAL-CARBON COMPOSITE AND PLATINUM-ELECTRODES

The use of a newly developed stainless steel-carbon composite electrod e designed for energy storage device applications is introduced. An ex perimental comparison of the electrochemical properties of 'electrocoa ted'' cast (SC) Nation film modified electrodes is described. Specific ally, the oxygen reduction reaction (ORR) at bare and Nation-modified stainless steel-carbon composite electrodes in 0.1 M NaOH and at bare an platinum disk electrodes in 0.7 M H3PO4 using cyclic voltammetry, c hronoamperometry, an ac impedance analysis. The reduction currents, re duction current enhancement factors, Tafel slopes, and exchange curren t densities observed at the Nation-modified electrodes are compared wi th the values observed at the bare electrodes in the same solution. Th e EC film electrodes show improved electrode kinetics compared with th e SC film electrodes based on the anodic shift of the reduction curren t E(p/2) values. In addition, the EC film electrodes exhibit larger pe ak of limiting current densities per unit weight Of Nation. The increa sed kinetics and larger reduction currents result from a higher concen tration of oxygen available at the electrode surface due to an increas ed interfacial contact area between the polymer and the electrode surf ace provided by the electrocoating method. Contact resistance between the polymer and the electrode surface may be reduced at EC film electr odes leading to less ohmic loss.