Hydrogen sensors based on conductivity changes in polyaniline nanofibers

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Polyaniline nanofibers offer enhanced properties due to their high surface area and porous structure.
• Understanding gas interactions with conductive polymers is crucial for developing novel sensors.
• Previous studies on polyaniline gas sensing have shown varying responses to different analytes.

Purpose of the Study:

• To investigate the response of camphorsulfonic acid doped polyaniline nanofibers to hydrogen gas.
• To explore the influence of humidity and oxygen on the hydrogen sensing mechanism.
• To elucidate the interaction mechanism between hydrogen and polyaniline nanofibers using isotope effects.

Main Methods:

• Fabrication of camphorsulfonic acid doped polyaniline nanofibers.
• Electrical resistance measurements of nanofiber films exposed to hydrogen/nitrogen mixtures.
• Quartz crystal microbalance (QCM) mass sensing to study gas uptake.
• Comparative studies using hydrogen and deuterium isotopes.

Main Results:

• Hydrogen caused a reversible decrease in polyaniline nanofiber resistance (3% for 1% H2/N2).
• Humidity completely suppressed the hydrogen response, while oxygen did not.
• A significant deuterium isotope effect was observed, with hydrogen yielding a larger response than deuterium (4.1 ± 0.4).
• Mass sensors confirmed the isotope effect, indicating preferential interaction with hydrogen over deuterium.
• Nanofiber structure facilitates gas diffusion, leading to an order of magnitude greater resistance change than conventional polyaniline.

Conclusions:

• Polyaniline nanofibers exhibit a strong, reversible response to hydrogen, attributed to their unique structure.
• The interaction mechanism likely involves hydrogen bonding to amine nitrogens, with humidity competitively binding to active sites.
• The observed deuterium isotope effect provides key insights into the gas-surface interaction dynamics.
• These findings support the potential of polyaniline nanofibers as sensitive hydrogen gas sensors and may be relevant to hydrogen storage claims.