Development and test of a highly sensitive and selective hydrogen sensor system

A miniaturized field-applicable sensor system was developed for the measurement of hydrogen (H2) in air in the concentration range 0.2–200 ppmv. The sensor system is based on the application of an yttria-stabilized zirconia (YSZ) solid electrolyte cell (SEC) as a coulometric detector with gas chromatographic (GC) pre-separation. The main system components for injection, chromatographic separation, and the oxygen pumping cell were significantly miniaturized and tested separately to characterize important measurement properties like selectivity, lower limit of detection, repeatability, and signal-to-noise ratio. Measurements were conducted under varying GC parameters and detector operating conditions. While changing the detector temperature influences the hydrogen peak significantly due to diffusion processes at the electrode–electrolyte interface; different oxygen-partial pressures at the measuring electrode have no visible effect. The combination of two packed columns with 1 m length, one filled with a molecular sieve (13X) and the other one with silica gel, enabled highly reproducible and selective H2 measurements with more than 90 % analyte turnover compared to Faraday's law. The resulting insights were used to define appropriate system parameters, construction guidelines, and material properties for the final test prototype.