First-principles Study Of The Enhanced Interfacial Adsorption Of Graphene Oxide/Iron-based Materials Induced By Functional Groups

Steel is the most important alloy material in modern industry,and the wear and corrosion on its surface have seriously hindered the development of social economy.As a derivative of two-dimensional material graphene,graphene oxide can be used as an efficient organic coating to protect the steel surface owing to its good dispersion,chemical resistance and non-toxicity.In this paper,from the nanometer scale,the adsorption mechanism of graphene oxide on steel surface was studied by means of the first-principles calculations.We focused on investigating the effect of oxidized functional groups on the interfacial adsorption strength.The main research contents are as follows:Two types of iron-based materials were used to replace steel and the simulation models were prepared:Fe(110)and Fe₂O₃(0001)surfaces,two stable structures of iron oxide are constructed according to the relative humidity in the environment.One is the Fe₂O₃-O substrate with O atoms as the adsorption surface,and the other is the Fe₂O₃-Fe substrate with Fe atoms as the adsorption surface.Graphene oxide/iron-based material composite system was built,and graphene/iron-based material as a comparison model,then the reasonable geometric optimization methods were established.The adsorption of graphene and graphene oxide on Fe(110)substrate was simulated,and the stable adsorption configuration of these two types of composite systems in equilibrium state was obtained.Through out-of-plane displacement calculations,it was observed that the functional groups of graphene oxide induce its neighboring C atoms to press down and closer to the substrate surface,forming stronger C-Fe bonds at the local regions;The interfacial binding energy of these two types of composite structure is calculated,it was found that graphene oxide has a stronger interaction with the Fe substrate compared to graphene,and by increasing the number of functional groups can significantly enhance the interfacial binding energy.The increase in binding energy results from the enhancement of the chemical bonding interaction at the interface,while the van der Waals interaction is hardly affected by the functional groups;Through analyzing the electronic structure of these two types of systems,the enhancement mechanism for the local C-Fe chemical bond around the functional groups is revealed,that is,the functional groups induce a stronger charge transfer between its neighboring C atoms and the Fe atoms underneath.Meanwhile,the corresponding C 2p-Fe 3d orbital hybridization is also enhanced.The adsorption of graphene and graphene oxide on Fe₂O₃-Fe and Fe₂O₃-O substrates was simulated,and the stable adsorption configuration of these four types of composite systems in equilibrium state was obtained.It was observed that only in the case of Fe₂O₃-O substrate,and the functional group is connected to the neighbor point of the top site carbon,the interface spacing between graphene oxide layer and iron oxide surface can reach the typical value of chemisorption,and the binding energy is greatly increased compared to the case of pure graphene;By electronic structure calculations,the bonding between graphene oxide C and substrate O was further investigated,and it was found that the strong C-O covalent bonds have been formed at the interface;For other adsorption configurations,the presence of functional groups only makes the graphene oxide layer slightly closer to the iron oxide substrate,the binding energy is enhanced but the amplitude is not large,and it still belongs to physisorption.The research content of this work helps to understand the adsorption mechanism of graphene and graphene oxide on iron-based materials,as well as the inherent microscopic mechanism of the adsorption enhancement of graphene oxide on the iron-based material surface induced by the functional groups,the present results have a certain theoretical guiding significance for the development of new graphene-based protective coatings with enhanced adhesion performance on steel.