Abstract
An electrochemical hydrogen sensor has been constructed, based on two platinum electrodes that differ in their true-to-geometrical surface area ratios and that are in contact with Nafion. The electrodes attain different mixed potential values in air containing hydrogen and thus the sensor does not require a reference atmosphere (pure air).
The potential difference between the electrodes can be used for potentiometric or amperometric detection of hydrogen. The detection sensitivity strongly depends on the relative humidity (RH) of the test air.
Within a hydrogen concentration range from 40 to 4000ppm (v/v) and with RH varying between 33 and 95%, the sensitivity of potentiometric detection decreases with increasing RH from 149 to 113 mV per concentration decade, while that for amperometric detection increases from 0.67 to 1.25 nA/ppm. On a step change in the hydrogen concentration, a value of 95% of stationary response is attained within ca. 140 s for potentiometric detection and ca. 50s for amperometric measurement.