Tetraoxa[8]circulene Monolayer as Hydrogen Storage Material: Model with Boys–Bernardi Corrections Within Density Functional Theory

Abstract

The parameters of molecular hydrogen adsorption on a tetraoxa[8]circulene monolayer were studied using the density functional theory with dispersion interaction corrections (semi-empirical and analytical). The calculations were carried out using two different approaches to the system wave function representation: atomic-like orbital basis set and plane wave basis. Utilizing a less computationally expensive pseudo-atomic basis, it is possible to obtain results for molecular hydrogen adsorption consistent with values calculated with plane waves if the atomic-like basis is optimized and basis set superposition error is corrected for both hydrogen binding energy and geometrical characteristics. Otherwise, the H₂ binding energy will be overestimated by 4–6 times (sometimes even more, by 20); and the hydrogen–monolayer distance will be underestimated by 10–20%. The obtained optimized parameters of the pseudo-atomic basis set can be used for further study of the modified forms of the tetraoxa[8]circulene monolayer. Moreover, our calculations showed that the hydrogen binding to a pristine tetraoxa[8]circulene monolayer is predominantly van der Waals with an energy of 60–90 meV, which is several times less than the desired range of 200–600 meV. To achieve such values, it will be necessary to modify the surface of the monolayer, creating more active sorption cites, for example, by decorating it with metals or applying structural defects.