Kinetics of oxygen transfer reactions on the graphene surface. Part II. H2O vs. CO2. (30th August 2020)

• Record Type: Journal Article
• Authors: Oyarzún, Andrea M.; García-Carmona, Ximena; Radovic, Ljubisa R.
• Is Part Of: Carbon. Volume 164(2020)
• Page Start: 85
• Page End: 99
• Publication Date: 2020-08-30
• Subjects: Carbon -- Periodicals; Carbone -- Périodiques; Koolstof; Toepassingen; Electronic journals; 546.681
• DOI: 10.1016/j.carbon.2020.01.011
• Languages: English
• ISSNs: 0008-6223

Abstract

Abstract: This computational chemistry analysis compares the interactions of H2 O and CO2 with zigzag graphene edges, and in particular their adsorption and desorption steps. We provide detailed information regarding the geometric and electronic factors that influence both their adsorption and desorption (of H2 and CO) processes. Density functional theory results are compared with experimental information to offer heretofore unavailable insights into key aspects of the rate-limiting steps, inhibition phenomena and nanoscale differences in these two reactions. Thus, for example, the orientation and rotation of the adsorbing H2 O molecules are elucidated using intrinsic reaction coordinate calculations and molecular orbital analysis, and these results complement recent pulse field gradient NMR measurements and molecular dynamics calculations. Such mechanistic findings reveal the H2 O adsorption process to be a slow rotational phenomenon whereas the low-temperature H2 desorption is geometrically constrained by the presence of contiguous (di)hydrogenated carbon atoms with or without hydroxyl groups. This surface-assisted desorption mechanism is proposed to be responsible for the formation of hexagonal pits during the graphite-H2 O reaction. Similar insights were obtained for the graphene-CO2 reaction. Mechanistic schemes are proposed for the desorption products observed in experiments, distinguishing zigzag from armchair sites. Graphical abstract: Image 1