New Analytical Method for Measurement of Hydrogen Partial Pressure Using a Tubular Hydrogen Pump-Gauge

A tubular hydrogen pump-gauge was constructed and applied to measure hydrogen partial pressure by using a new analytical equation. The merit of using the equation is that a reference gas with a known hydrogen partial pressure is not necessary; in fact, the method worked well when the reference gas was Ar/H₂/H₂O or air/H₂O. Sample gases, containing up to 1% by volume hydrogen in argon and including water vapor, were flowed through a non-porous tube of a proton conductor operated at temperatures in the range 700–800 °C. Current was passed via one pair of porous platinum electrodes to pump hydrogen electrochemically in or out of the gas flowing in the tube. A second pair of electrodes downstream enabled a Nernst emf to be monitored. Passing a current, I, resulted in a change in Nernst emf, ΔE. A new theoretical equation predicted a linear relationship between exp(−2FΔE/RT) and I at constant gas flow rate within the tube, and also between exp(−2FΔE/RT) and the reciprocal flow rate at constant I. Measurements validated these predictions at hydrogen partial pressures up to 5 × 10⁻⁴ atm.