氧原子在氟化石墨烯上扩散的第一性原理计算

First-principles calculations of O-atom diffusion on fluorinated graphene

石墨烯的氟化是改善石墨烯涂层腐蚀防护能力的有效方法之一.本文使用NEB过渡态搜索方法研究了O原子在完全氟化石墨烯(CF)和部分氟化石墨烯(C_(4)F)上的扩散和穿透行为,分析F原子对石墨烯薄膜抗腐蚀能力的影响.计算结果显示,F原子的吸附能有效抑制O原子在石墨烯上的扩散,C_(4)F上O原子的表面扩散能垒显著提高,CF内O原子的水平扩散能垒更是高达2.69 eV.而且F原子的增加使得C原子层对O原子穿透的阻隔能力减小,在CF中,O原子的穿透主要受到F原子层的阻隔.此外采用第一性原理计算方法计算了纯石墨烯、CF和C_(4)F薄膜与Cu(111)表面的界面粘附功以及电子结构.计算表明,相比于纯石墨烯,CF和C_(4)F能更好地与基底结合,界面粘附功随着F原子的吸附浓度增大而提高.Cu/C_(4)F和Cu/CF界面的电荷转移均增加,其中Cu/C_(4)F界面的电荷转移更多,C_(4)F与Cu(111)表面的部分Cu原子生成Cu—C键.

Fluorination of graphene is one of the most effective methods to improve the corrosion protection of graphene coatings.In this work,the diffusion and penetration behaviors of O atoms on fully fluorinated graphene(CF)and partially fluorinated graphene(C_(4)F)are investigated by using the method of searching for NEB transition state.The effects of F atoms on the corrosion resistance of fluorinated graphene films are also analyzed r.The results show that the adsorption of F atoms can effectively inhibit the diffusion of O atoms on graphene.On C_(4)F,the F atoms are distributed in a para-top position,which greatly increases the surface diffusion energy barrier of O atoms.Moreover,it is difficult for the adsorbed O atoms to diffuse to different sp^(2)C rings through the obstruction of F atoms.The energy barrier of the horizontal diffusion of O atoms even reaches 2.69 eV in CF.And with the increase of F atoms,the stable structure of graphene is gradually destroyed,the ability of C-atom layer to bar the penetration behaviors of O atoms decreases greatly.Furthermore,the inter facial adhesion work of pure graphene,CF and C_(4)F films with Cu(111)surfaces are calculated,as well as the electronic structures of the composite interface are investigated by using firstprinciples calculations.The interfacial adhesion work of the Cu/G,Cu/C_(4)F and Cu/CF interfaces are 2.626 J/m^(2),3.529 J/m^(2) and 3.559 J/m^(2),respectively.The calculations show that the bonding of C_(4)F and C_(4)F with Cu substrate are stronger than pure graphene with Cu substrate,and the inter facial adhesion work increases with the augment of F atom adsorption concentration.The calculation of the density of states also conforms that the interaction between Cu and C atoms of the Cu/C_(4)F interface is stronger than that at the Cu/CF interface.Bader charge analysis shows that the charge transfer at the Cu/C_(4)F interface and the Cu/CF interface increase comparing with that at the Cu/G interface,and Cu/C_(4)F interface has more charge transfer,in which Cu—C bonds are formed.