Electrostimulated Desorption Hydrogen Sensor Based on Onion-Like Carbons as a Sensing Element

Within this paper, a hydrogen sensor based on onion-like carbons (OLCs) is proposed and its behaviour is assessed in detail. The OLCs prove to be ideal candidates for the development of solid-state sensing technology of hydrogen working at room temperature, due to their hydrophobic nature and their non-porous texture. Using dielectrophoreis as a method of electromanipulation, the OLCs undergo ultrasonication in ethanol and, according to the analysis results through the Fourier transform infrared (FT-IR) spectra of OLC/C2H6O nanoparticles showed significant structural changes compared to the pristine OLCs. The fullerene C60 nanoparticles exposed to ethanol can present several solvation shells around the central fullerene molecule, and in the first layer of the solvation shell, ethanol molecules tend to form non-polar alkyl groups exposed to the surface, which contributes to the stimulation of structural defects of the OLC layers. The fast decrease in resistance of the OLC/C2H6O sensor under 10 ppm H2 exposure can be attributed to the switch of the nanoparticles to n-type semiconductor behaviour together with the additional increase in the number of electrons in the conduction band. Countless carbon-based sensing devices were previously reported, but the major drawback of these solutions was the irreversible response to hydrogen because of the high energy required by the adsorbed binding molecules to desorb from the material at low working temperatures. The sensor presented exploits the binding capacity of hydrogen to OLCs/C2H6O, as demonstrated by the previously proposed hydrogen storage solutions based on these fullerenes. In order to ensure sensors enhanced operability at room temperature current, stimulated desorption was used to stimulate desorption of the analyte molecules in the absence of an external heating source.