Self-referenced electrode for galvanic cell-type hydrogen and steam sensors

A self-referenced electrode was devised for galvanic cell-type hydrogen and steam sensors. Two proton-conducting solid electrolyte discs with porous platinum electrodes, one for electrochemical pumping of hydrogen and the other for sensing of hydrogen or water vapor, were stacked and exposed to test gases at 500-600°C; a small open pore was provided in the sensing electrolyte. When a constant current was sent to the pumping cell to draw out hydrogen at the interface of the two cells, the sensing cell indicated EMF as a function of hydrogen or water vapor activity in the test gas. This suggest that the hydrogen activity at the interface could be controlled with respect the test gas atmosphere, based on the equal rate of the hydrogen pumping and hydrogen or water vapor diffusion through the pore at the stationary state.