The Role of Molecular Dications From the Astrochemistry to Plasma Assisted CO2 Methanation

Molecular dications are doubly charged cations of importance in flames, plasma chemistry/physics and in the chemistry of the upper atmosphere of planets. Furthermore, they are exotic species able to store a considerable amount of energy at a molecular level. This high energy content of several eV can be easily released as translational energy of the two fragments mono-cations generated by their Coulomb explosion. For such a reason, they were proposed as a new kind of alternative propellants.1 Following the interesting discussion that opened in the early 2000s in the scientific community concerning the possible role of molecular dications in the upper atmosphere of planets, we were able to propose an explanation of the lack in the O+ expected concentration of the Mars atmosphere, as measured by MARINER 6 spacecraft and VIKING 1 lander, invoking the atmospheric escape of O+ by dissociative double photoionization of CO2 molecules via Coulomb explosion of the metastable intermediate CO22+ dication.2 Therefore, this process can in principle contribute to the continuous erosion of the atmosphere of this planet. Inspired by these results, we decided to use our thirty years of experience in the generation and characterization of plasmas to explore the possibility of increasing the chemical reactivity of CO2+H2 reagent mixtures, used in methanation processes exploiting the Sabatier reaction3 by plasma assisted catalysis. The idea is to generate plasmas on CO2+H2 mixtures and to verify whether the formation of CO22+ dications, followed by Coulomb explosion with the production of CO+ and O+ fragments which have a high relative kinetic energy (of about 6.0 eV), increases the chemical reactivity which leads to the hydrogenation of carbon dioxide towards hydrocarbons or other useful organic substances.4,5 The preliminary results obtained will be presented at the Conference. References [1] S. Falcinelli, M. Rosi, Production and Characterization of Molecular Dications: Experimental and Theoretical Efforts, Molecules 2020, 25,4157. [2] S. Falcinelli, F- Pirani, M. Alagia, L. Schio, R. Richter, S. Stranges, F. Vecchiocattivi, The escape of O+ ions from the atmosphere: An explanation of the observed ion density profiles on Mars, Chem. Phys. Lett. 2016, 666, 1-6. [3] S. Falcinelli, A. Capriccioli, F. Pirani, F. Vecchiocattivi, S. Stranges, C. Martì, A. Nicoziani, E. Topini, A. Laganà, Methane production by CO2 hydrogenation reaction with and without solid phase catalysis, Fuel 2017, 209, 802-811. [4] S. Falcinelli, Fuel production from waste CO2 using renewable energies, Catalysis Today 2020 348, 95-101. [5] S. Falcinelli, A. Capriccioli, M. Rosi, C. Martì, M. Parriani, A. Laganà, Methane Production from H2 + CO2 Reaction: An OpenMolecular Science Case for Computational and Experimental Studies, Physchem 2021, 1(1), 82–94.