Self-healing superhydrophobic conductive coatings for self-cleaning and humidity-insensitive hydrogen sensors

Hydrogen (H2) sensors are widely used in applications such as chemical refining, semiconductor processing, fuel cells, and hydrogen storage/separation. However, their sensing performance and service life are highly prone to contamination by dust, water, and humidity. To solve this problem, in this study, we report the fabrication of self-healing superhydrophobic H2 sensors by spray coating a mixture of palladium (Pd) nanoparticle-decorated multiwalled carbon nanotubes (Pd-CNTs), polydimethylsiloxane (PDMS), and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS). The resulting Pd-CNTs/PDMS/POTS sensors exhibit a good conductivity, excellent superhydrophobicity, and stable H2 sensing ability at room temperature with a detection range of 100–10,000 ppm H2 in air. The integration of superhydrophobicity makes the Pd-CNTs/PDMS/POTS sensors highly water repellent to prevent water damage, self-cleaning to remove dust contamination, and humidity-insensitive to maintain the H2 sensing performance under highly humid environments. More importantly, when the superhydrophobicity is chemically damaged, the Pd-CNTs/PDMS/POTS sensors are capable of spontaneously and repeatedly healing their damaged superhydrophobicity through the migration of POTS and PDMS from the bulk, guaranteeing long-term protection to the H2 sensors. Additionally, owing to the electrothermal conversion ability of CNTs, the temperature of Pd-CNTs/PDMS/POTS sensors can be readily increased to 50.1 °C by applying a potential of 6.0 V, which greatly accelerates the self-healing process of the sensors.