How boron is adsorbed by oxygen-containing groups functionalized graphene: A density functional theory study

Abstract

We employed density functional theory to investigate the adsorption mechanism of B(OH)3 and B(OH)4− on different graphene models: graphene with 20 carbon rings (G20), hydroxyl-modified graphene (G20-OH), and carboxyl-modified graphene (G20-COOH). The enthalpy of adsorption for B(OH)3 and B(OH)4− was as follows: G20 (−9.24 and −3.51 eV), G20-OH (−9.38 and −3.89 eV), and G20-COOH (−10.28 and −4.83 eV). The free energy of adsorption values were: G20 (−8.82 and −3.16 eV), G20-OH (−8.85 and −3.45 eV), G20-COOH (−9.66 and −4.27 eV). B(OH)3 exhibited easier adsorption than B(OH)4− within these groups. The interaction forces between B(OH)3/B(OH)4− and oxygen-containing groups were quantified, highlighting their role in determining the differential adsorption of B(OH)3 and B(OH)4−. Hydrogen bonding, van der Waals interaction, and steric effects were the main contributing factors to the adsorption process. G20 displayed stronger van der Waals forces with B(OH)3 than with B(OH)4−, while G20-COOH exhibited significantly stronger van der Waals forces with B(OH)3. The decreased steric hindrance contributed to the increased adsorption of G20-COOH with B(OH)3. Hydrogen bonding and reduced van der Waals forces played a role in the higher adsorption of G20-COOH with B(OH)4−. These findings inform strategies for efficiently removing boron species by understanding their adsorption mechanism on graphene.