Interactions between Reduced Graphene Oxide with Monomers of (Calcium) Silicate Hydrates: A First-Principles Study.

Mohammadreza Izadifar,Peter Thissen,Andres Ayuela,Jorge S Dolado

doi:10.3390/nano11092248

Abstract

Graphene is a two-dimensional material, with exceptional mechanical, electrical, and thermal properties. Graphene-based materials are, therefore, excellent candidates for use in nanocomposites. We investigated reduced graphene oxide (rGO), which is produced easily by oxidizing and exfoliating graphite in calcium silicate hydrate (CSHs) composites, for use in cementitious materials. The density functional theory was used to study the binding of moieties, on the rGO surface (e.g., hydroxyl-OH/rGO and epoxide/rGO groups), to CSH units, such as silicate tetrahedra, calcium ions, and OH groups. The simulations indicate complex interactions between OH/rGO and silicate tetrahedra, involving condensation reactions and selective repairing of the rGO lattice to reform pristine graphene. The condensation reactions even occurred in the presence of calcium ions and hydroxyl groups. In contrast, rGO/CSH interactions remained close to the initial structural models of the epoxy rGO surface. The simulations indicate that specific CSHs, containing rGO with different interfacial topologies, can be manufactured using coatings of either epoxide or hydroxyl groups. The results fill a knowledge gap, by establishing a connection between the chemical compositions of CSH units and rGO, and confirm that a wet chemical method can be used to produce pristine graphene by removing hydroxyl defects from rGO.

Highlights

We were interested in investigating the mechanism involved in the interaction between Si(OH)4 hydrated silicate monomers and hydroxyl/reduced graphene oxide (rGO)
In a neutral system was placed as another initial simulation model, and we found that the hydrogen becomes dissociated from the hydroxyl/rGO surface and is transferred to the ThisThis indicates thatthat a hydrogen atomatom becomes dissociated fromfrom the hyto the indicates a hydrogen becomes dissociated the surface regardless of whether system chargedororneutral
A density functional theory (DFT) method was used to study the mechanism involved in the interactions between hydroxyl or epoxide rGO and the calcium silicate hydrate gel (CSH) moieties, such as CSH gel in cement

Summary

Introduction

Graphene [1] is a two-dimensional honeycomb plane of sp carbon atoms, and has received considerable attention for its use in applications such as electronic devices [2], energy storage devices [3], and composite materials [4,5], because of its unique mechanical [6,7], electronic [8], thermal [9,10,11,12], and chemical properties [13,14,15,16,17]. Graphene can be produced by chemical vapor deposition (CVD), using a catalytic metal substrate made of materials such as Cu or Ni [18,19], or by mechanical and chemical exfoliation of graphite, with deposition of the exfoliated pieces on various substrates [1,15,20]. The chemical vapor deposition method involves the use of high-temperature procedures and specialist equipment, and is a relatively expensive method of producing graphene with very few defects. A great deal of attention has been paid to the development of methods involving the chemical oxidation and exfoliation of graphite, to yield graphene oxide (GO), with the subsequent reduction in the oxygen-containing functional groups, using thermal, chemical, or electrochemical reduction methods, to yield reduced graphene oxide (rGO), 4.0/).

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Conclusion