CMD30 FisMat2023 - Submission - View

Abstract title: Atomic Deuterium Bonding to Vertically Aligned Multi-Walled Carbon Nanotubes.
Submitting author: Sammar Tayyab
Affiliation: Department of Physics and INFN, Sapienza University of Rome.
Affiliation Address: Piazzale Aldo Moro 2, 00185 Rome, Italy.
Country: Italy
Other authors and affiliations: Alice Apponi (Department of Science and INFN, University of Roma Tre, Via della Vasca Navale 84, 00146 Rome, Italy), Maria Grazia Betti (Physics Department, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy), Gianluca Cavoto (Physics Department and INFN, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy), Riccardo Frisenda (Physics Department, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy), Dario Marchiani (Physics Department, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy), Carlo Mariani (Physics Department and INFN, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy), Francesco Pandolfi (INFN Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy), Ilaria Rago (Physics Department and INFN, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy), Alessandro Ruocco (Department of Science and INFN, University of Roma Tre, Via della Vasca Navale 84, 00146 Rome, Italy), Ravi Prakash Yadav (Physics Department and INFN, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy).
Abstract
Hydrogen is considered an efficient energy carrier, a renewable, storable, abundant resource and has reduced impact on the environment. Efficient storage of hydrogen will play a key role in many applications and one of the most appropriate ways to store it is in solid-state materials. Carbon Nano-Tubes (CNTs) are considered as one of the most effective potential candidates for hydrogen storage as they present high surface area, light weight, chemical and mechanical stability. CNTs are constituted by rolled graphene sheets made up of sp2 bonding network of carbon atoms [1], and atomic hydrogen (H) chemisorption causes the C–C sp2 bonds of pristine CNTs to be modified towards sp3 H–C bonds. The chemical reactivity with H has been predicted to be enhanced by the local curvature of the C mesh [2], thus suggesting the use of CNTs as efficient storage systems. In this work, we present atomic deuterium (D) chemisorption on highly aligned multi-wall C nanotubes (MWCNTs), being D a H isotope with the same chemical reactivity. Samples have been grown by chemical vapor deposition (CVD) on Si wafers, following an established procedure [3]. A forest of vertically highly aligned CNTs, with average height of 180 mm and average diameter of 20 nm, as analyzed by Scanning Electron microscopy (SEM), has been used for D uptake. X-Ray photoelectron spectroscopy (XPS) of the C1s core level at pristine MWCNTs, shows the dominant component related to the sp2 bonding, accompanied by the plasmon associated to pi collective excitations [4]. Atomic deuterium is obtained by dissociation of D2 molecules with a hot capillary in ultra-high-vacuum (UHV) conditions. D chemisorption on CNTs is demonstrated by studying the evolution of the C 1s core level line-shape, with the emerging of a neat sp3 component, due to the D-C established bonds. The intensity of the sp3 component is a sign of bond deformation with respect to pure pi bonding and evidence to the establishment of D-C chemical bonding when CNTs are exposed to D [4]. We estimate the at.% D:C ratio with the sp3/[sp3+sp2] components’ intensity ratio, reaching nearly 70 at.% D:C upload in MWCNTs, much higher than that obtained by other deposition methods so far [5].This research on deuterium chemisorption on CNTs and graphene meshes, beyond its importance for the storage, is also in line with the development of recently proposed potential new anisotropic detectors exploiting higher mass isotopes of hydrogen [6].                                                                                                                                                                                                 References:
  1. Nikita, G. et al. Carbon Letters. 29, 419–447, (2019)
  2. Apponi et al. (Ptolemy collab.), Phys. Rev. D 106, 053002 (2022)
  3. Kumar and Ando; J. Nanosci. Nanotechnol. 10, 3739–3758, (2010)
  4. Betti et al. Nano Letters. 22, 2971-2977, (2022).
  5. Tokura et al. Carbon 46, 1903-1908, (2008).
  6. Betti et al. (Ptolemy collab.), Prog. Part. Nucl. Phys. 106, 120 (2019).