Naphthoquinone-silicate based gas electrodes: Chemical-electrochemical mode of operation

We demonstrate a new type of gas electrode composed of a porous matrix of carbon powder and redox polymer binder. Homogenous reaction of the target gaseous compound with the redox functional groups of the polymer produces a concentration gradient within the redox polymer. This gradient induces charge transport towards the carbon particles where electrodic regeneration of the redox groups takes place. Oxygen reduction on a naphthoquinone-modified carbon ceramic composite electrode (NPQ/CCE) demonstrates a new type of gas permeable electrode. A reaction-diffusion model for the gas electrodes is presented. The model predicts electrochemical charge transfer control at low overpotentials and either kinetic control or diffusion limitation at high overpotentials. Predicted current-potential curves of the composite electrode are compared to the observed polarization curves for oxygen reduction on redox-silicate-carbon gas electrodes. Oxygen sensing on NPQ-modified CCE is demonstrated.