Interplay between van der Waals, Kubas, and chemisorption process when hydrogen molecules are adsorbed on pristine and Sc-functionalized BeN4

• Published in: International journal of hydrogen energy Vol. 50; pp. 1302 - 1316
• Main Authors: Mahamiya, Vikram, Dewangan, Juhee, Chakraborty, Brahmananda
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 02.01.2024
• Subjects: 2D nanomaterials; Adsorption energy; Beryllonitrene; Density functional theory; Gravimetric density; Hydrogen storage; Density functional theory; Hydrogen storage; Adsorption energy; 2D nanomaterials; Beryllonitrene; Gravimetric density
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.09.151

Inspired by the recent successful synthesis of the Dirac material BeN4, the interaction of dihydrogen with pristine and Sc-functionalized BeN4 is investigated using dispersion-corrected density functional theory and ab-initio molecular dynamics simulations. The simulation results show that hydrogen molecules are physisorbed to pristine BeN4 with an adsorption energy of −0.12 eV and have low H2 uptake (∼1.3 wt%) at 100 K. Functionalization of the scandium atom on BeN4 monolayer enhances adsorption energy and desorption temperature of hydrogen molecules beyond room temperature, as calculated from ab-initio molecular dynamics simulations. Using the DFT-D2 and DFT-D3 dispersion corrected DFT, we report that each Sc atom functionalized on BeN4 surface can reversibly adsorb five hydrogen molecules through Kubas interactions with an average adsorption energy of −0.53 and −0.42 eV/H2, respectively. The storage capacity of hydrogen for Sc-decorated BeN4 is 7.86 wt% at room temperature, which drops to 6% at 400 K. At 500 K, three hydrogen molecules get desorbed from the Sc-decorated BeN4, and the remaining two dissociate into isolated H-atoms, leading to irreversible hydrogen storage. The diffusion barrier for the clustering of Sc atoms is found to be 3.41 eV, calculated using the CI-NEB method. This study builds an understanding of the interaction mechanisms responsible for practically suitable hydrogen uptake in metal-functionalized 2D nanomaterials. [Display omitted] •We investigate the interaction between BeN4(Sc functionalized BeN4) and H2 by performing DFT and AIMD simulations.•Sc-decorated BeN4 can adsorb up to 7.86% H2 at room temperature, which drops to 6% at 400 K.•The attached dihydrogen molecules get dissociated into isolated H atoms above room temperature.•The isolated H-atoms are bound to Sc by pure chemisorption interactions.•The CI-NEB method calculates a diffusion energy barrier of 3.41 eV for the clustering of Sc atoms.