First-Principles Study On Anti-Oxidative Behavior Of Non-metallic Doped Copper-Based Graphene Coatings In Marine Environment

Copper and its alloys are more widely used in industry and daily life due to their excellent properties.Unfortunately,copper suffers from severe localized corrosion when applied in Cl-rich marine environments.Therefore,the development of an efficient anti-oxidative corrosion coating is a common,practical and preferred method for protecting copper and its alloys from corrosion damage.Graphene is used for anticorrosion and anti-oxidation coatings due to its excellent shielding properties,but experiments show that the anti-corrosion ability of graphene is not as excellent as the theoretical one,and the diffusion behavior of oxygen will exacerbate the formation of "edge tearing" of graphene.Corrosion of copper substrates.Therefore,in this paper,through first-principles computational simulations based on density functional theory,from the perspectives of kinetics and thermodynamics,the adsorption structure,adsorption energy,density of states,diffusion energy barriers and differences of oxygen and Cl on copper-based graphene are analyzed.The calculation results of density and charge are analyzed to explore the adsorption and diffusion mechanism of oxygen on graphene/defective graphene on the surface of copper substrate in marine environment.In addition,four kinds of non-metallic doped graphene on copper substrates including B,P,S and Si were selected to improve its oxidation and corrosion resistance in marine environment.The main findings are as follows:1)The adsorption-diffusion behavior of oxygen on the graphene layer on the copper surface under the atmospheric environment(Cl-free)was simulated by calculation.The adsorption energy results show that the presence of the copper substrate significantly promotes the adsorption of oxygen atoms,and the diffusion energy barrier results show that the presence of the substrate copper makes it easier for oxygen to diffuse in the graphene,which makes the graphene on the copper substrate easier to crack and fail,thereby accelerating the corrosion phenomenon.The doping results show that the adsorption energy of oxygen on Si-doped graphene is the smallest,and the adsorption energy is the largest on S-doped graphene.The diffusion energies of oxygen atoms on B-doped graphene are all positive values,slightly lower than the diffusion energy barrier on S-doped graphene,but oxygen has the maximum energy during the diffusion process on S-doped graphene.release,and therefore,B-doped graphene on copper substrates may have the best anti-corrosion and anti-oxidation properties in atmospheric environments.2)The simulation calculates the diffusion of oxygen on the intact graphene on the copper surface in a harsher marine environment(containing Cl).The results show that the presence of copper substrate enhances the adsorption energy of Cl on graphene.The presence of Cl atoms promotes the adsorption of oxygen atoms on graphene.The diffusion energy barrier results indicate that the presence of Cl promotes the diffusion efficiency of oxygen atoms on graphene.In the marine environment,the adsorption energy of oxygen on P-doped graphene is the lowest.Si-doped graphene has the highest diffusion energy barrier(2.14 e V)in the marine environment,and the diffusion energy barrier on B-doped graphene is 0.76 e V.Therefore,in the marine environment,Si-doped graphene has the best anti-corrosion and anti-oxidation performance in the marine environment,followed by B-doped graphene,and the anti-corrosion and anti-oxidation performance of P-doped graphene may be unsatisfactory.3)Further explore and calculate the penetration diffusion of oxygen on copper surface defect graphene in marine environment.The calculation results show that the presence of substrate copper significantly improves the adsorption of oxygen on graphene,and the adsorption energy of oxygen on defective graphene is much greater than that on non-defective graphene.The oxygen diffusion barrier(1.72 e V)on defective graphene in marine environment indicates that Cl can significantly improve the oxygen penetration and diffusion ability in copper-based graphene.The doping results indicate that S-doped graphene has higher covalent properties.After B-doped defect graphene,the adsorption energies of oxygen and Cl atoms are the lowest,and the oxygen diffusion barrier in B-doped defect graphene is the highest(3.71 e V).In summary,the presence of substrate copper promotes the oxidation corrosion of graphene itself.Graphene on B-doped copper substrate is most beneficial to reduce the diffusion of oxygen and the efficiency of penetrating graphene/defective graphene,thereby improving the corrosion resistance and oxidation resistance of copper-based graphene in marine environment.This study provides a theoretical basis for the application of B-doped copper-based graphene in marine environments.