Hydrogen Detection by Polyaniline Nanofibers on Gold and Platinum Electrodes

Polyaniline nanofibers were deposited on either gold or platinum electrodes and used as resistive sensors for the detection of hydrogen. In earlier work (J. Phys. Chem. B 2006, 110, 22266-22270), we showed that hydrogen interacts directly with polyaniline nanofibers to induce a small resistance decrease (-3%) at low concentrations of hydrogen (1%) using gold electrodes. This work showed that the sensor response on gold electrodes is due to hydrogen interaction with the polyaniline nanofibers. However, with platinum electrodes a much larger resistance increase (+65%) is observed under the same conditions. The sensor response on platinum electrodes is due to hydrogen interaction with platinum at the polyaniline-platinum interface. Hydrogen facilitates the formation of a Schottky barrier between platinum and polyaniline through a change in work function as platinum is converted to platinum hydride. The work function of polyaniline nanofibers was measured, and a model for sensor response is presented based on the relative work functions of the platinum, platinum hydride, and polyaniline nanofibers. Platinum hydride formation is fully reversible with the introduction of oxygen that converts the platinum hydride to water. The greater sensitivity of the platinum sensor can be used to detect hydrogen at a concentration of 10 ppm.