Hydrogen Sensors\nBased on Flexible Carbon Nanotube-Palladium\nComposite Sheets Integrated with Ripstop Fabric

Abstract

This work describes the design and fabrication of free-standing\ncarbon nanotube-palladium (CNT-Pd) composite sheets for hydrogen gas\nsensing. The CNT-Pd composites were made by electroplating palladium\nonto a solvent-densified and oxygen plasma-treated CNT sheet. The\nlatter was prepared using high purity CNTs drawn from a dense, vertically\naligned array grown by chemical vapor deposition on silicon substrates.\nThe CNT-Pd sheets were characterized by energy-dispersive spectroscopy,\nscanning electron microscopy, and X-ray diffraction. The amount of\npalladium in the composite was 16.5 wt % as measured via thermogravimetric\nanalysis. Thin strips of the CNT-Pd sheets were assembled as chemiresistor\nsensors and tested for hydrogen gas detection. The sensors demonstrated\na limit of detection of 0.1 mol % and displayed signal reversibility\nwithout the need for oxygen removal or heat treatment. A decrease\nin signal reversibility was observed after multiple exposure cycles;\nhowever, redensification with ethanol significantly restored the original\nreversibility. The sensor showed the Freundlich adsorption isotherm\nbehavior when exposed to hydrogen. The material’s potential\napplication toward a wearable, flexible sensor was demonstrated by\nintegrating the chemiresistor onto a fabric material using hot-press\nprocessing and testing the composite for hydrogen sensitivity.