The Response of the Stabilized Zirconia Galvanic Cell to Methane-Oxygen Mixtures

The voltage response of the stabilized zirconia galvanic cell to varying concentrations of methane‐air mixtures in their combustion products was studied, using air as a reference gas. It is shown that the cell can be operated in two distinct ways, the equilibrium and the nonequilibrium mode. In the former case, the electrode equilibrates the mixture completely and registers a Nernst potential corresponding to the oxygen partial pressure in the equilibrated mixture. With active porous platinum electrodes, this condition is realized. In the nonequilibrium case, the cell registers the Nernst potential corresponding to the true oxygen partial pressure in the mixture. This condition is realized with silver electrodes; exact oxygen potentials were obtained at temperatures as high as 800°C with mixtures containing up to 27% methane in air. By means of a combination of nonequilibrium and equilibrium electrodes, both oxygen and methane concentrations can be determined. A methane gauge is described that can measure methane in air without the use of a reference gas.