The main objective of this work is to improve the electronic and chemical properties of carbon nanotubes and other two-dimensional materials, such as nano-porous graphene, by doping the surface with alkali metals. One possible application is hydrogen storage, since the doping with potassium is expected to improve the bond between the hydrogen molecules and the graphene-lattice, thanks to an enhanced multipolar interaction, leading to a different desorption temperature and behaviour. This analysis will be carried out by temperature programmed desorption (TPD) to determine the adsorption energy, and by UV and X-ray photoelectron spectroscopy to characterize the bonding and electronic spectral density of states.
In this project I will take advantage of an ultra-high-vacuum-based deposition method which was well-calibrated during the last few years, and which showed a good performance both in terms of deposition rate and the quality of the obtained doping.
Furthermore, the presence of perfectly aligned carbon nanotubes (which surface will be cleaned by etching techniques) is expected to improve both the saturation of the alkali metal deposited material and the hydrogen uptake. Similarly, the quality of the surface in nano-porous graphene and other two-dimensional materials is really important.
The plan for this project is to use this high-quality deposition method and accurate control of the sample surface to improve the properties of the materials respect to the results published up to now, and to check them by Ultra-violet photoelectron and thermal desorption spectroscopy techniques, which are rarely used for this kind of analysis in similar samples, and thus can provide interesting and different feedback on the subject. This would help to strengthen the knowledge in this field and to increase the odds of obtaining important devices and applications.
We expect to determine: (i) the chemical bonding and electronic spectral density of states of pristine and K-decorated CNT and NPG; (ii) the modifications of the electronic properties after adsorption of both molecular (H2 and D2) and atomic (H and D) species; (iii) the adsorption energies of molecular (H2 and D2) and of atomic (H and D) species in the pristine CNT and NPG samples and in the K-decorated ones.