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. 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.