Advanced Oxygen Sensing for Accurate Gas Diffusivity Measurements in Fuel Cells

Impeded gas diffusion causes serious concentration polarization (CP) in fuel cells. The facile and accurate measurement of gas diffusivities in various electrodes facilitates the pre-evaluation of two key parameters in fuel cells, that is, the limiting current density (LCD) and CP. However, previously reported electrochemical devices for this purpose only employ a single oxygen voltage sensor, which induces inevitable voltage errors, owing to the existing oxygen gradient across the measurement tube. In this report, the correlation of such voltage errors with the errors of diffusivity measurement as well as the errors in pre-evaluating LCD and CP is analyzed quantitatively. A dual oxygen-sensing device is then proposed for the first time to eliminate the voltage errors, allowing for accurate diffusivity measurements and reliable pre-evaluation of LCD and CP in fuel cells with both bulk and thin nanostructured electrodes operated at different temperatures.