First-principles study on the interaction between Gr/GO and C-S-H gel units

Area of Science:

• Materials Science
• Computational Chemistry
• Nanotechnology

Background:

• Investigates interfacial interactions between graphene-based materials and calcium silicate hydrate (C-S-H) gel.
• Examines pristine graphene (Gr), graphene oxide (GO), and their defect variants (single-vacancy, double-vacancy, Stone-Wales).
• Focuses on the role of oxygen-containing functional groups and defects in modifying adsorption properties.

Purpose of the Study:

• To elucidate the atomic-level mechanisms governing the interaction between graphene/graphene oxide and C-S-H gel.
• To determine how various defects and functional groups on graphene influence adsorption strength and stability.
• To explore the synergistic effects of defects, functional groups, and ionic environments (Ca2+, OH-) on interfacial bonding.

Main Methods:

• Employs density functional theory (DFT) calculations using the CASTEP module.
• Utilizes GGA-PBE functional, ultrasoft pseudopotential, and DFT-D dispersion correction.
• Calculates adsorption energy, formation energy, and charge density difference to analyze interactions.

Main Results:

• Adsorption strength of Si(OH)4 on Gr/GO is polarity-dependent (GO-COOH > GO-OH > GO-O > Gr).
• Defects like SW and SV significantly alter adsorption energies and promote charge redistribution, especially for charged species (SiO(OH)3-).
• Ca2+ and OH- ions enhance stability through coordination and charge compensation, with synergistic effects from defects and functional groups.

Conclusions:

• Graphene defects and functional groups play a critical role in strengthening interfacial bonding with C-S-H gel.
• Specific functional groups (hydroxyl, carboxyl) form strong bonds with silicate chains, enhancing charge transfer.
• The combined presence of functional groups, defects, and ions creates robust adsorption centers, improving material interfaces.