Effect of thermal treatment on conductometric response of hydrogen gas sensors integrated with HCl-doped polyaniline nanofibers

• Observation of the effect of annealing on H2 sensors based on HCl-doped PANI.
• Revelation of crosslinking and partial carbonization of HCl-doped PANI upon annealing.
• Analysis of the influence of water and PANI's dopant on H2 sorption kinetics.

In this work, we investigated the effect of thermal treatments on the transduction of HCl-doped polyaniline (PANI) nanofibers integrated in conductometric devices upon exposure to 1% H2 (carried by N2). After drying in N2 at ∼25 °C for 12 h, our devices showed a ∼10% decrease in electrical resistance upon exposure to 1% H2. However, devices subject to 12-h drying in N2 at ∼25 °C followed by further thermal treatments in N2 at 100 °C, 164 °C or 200 °C for 30 min showed different transduction behaviors. The devices subject to thermal treatments at 100 °C and 164 °C showed a ∼7% decrease and <0.5% variation in electrical resistance, respectively. More interestingly, the device subject to the thermal treatment at 200 °C showed a transduction behavior with obvious opposite polarity, i.e. a ∼5% increase in electrical resistance upon exposure to 1% H2. Further analysis indicated that the observed results were related to the thermal treatments which caused HCl-doped PANI nanofibers to undergo (i) water desorption, (ii) crosslinking and/or (iii) partial carbonization.