CO与H2在应变Fe（110）表面的竞争吸附  

Competitive adsorption of CO and H2 on strained Fe（110） surface

作　　者：李守英 赵卫民[1] 乔建华 王勇 Li Shou-Ying;Zhao Wei-Min;Qiao Jian-Hua;Wang Yong(Schools of Materials Science and Engineering,China University of Petroleum (East China),Qingdao 266580,China;Schools of Mechanical and Electronic Engineering,Qingdao Binhai University,Qingdao 266555,China)

机构地区：[1]中国石油大学(华东)材料科学与工程学院,青岛266580 [2]青岛滨海学院机电工程学院,青岛266555

出　　处：《物理学报》2019年第21期264-270,共7页Acta Physica Sinica

基　　金：山东省自然科学基金(批准号:ZR2017MEE005)资助的课题~~

摘　　要：为研究CO降低临氢管线钢的氢脆机制,采用基于自旋极化密度泛函理论的第一性原理方法,研究H2和CO在Fe(110)表面吸附过程中的势能变化以及不同应变时的吸附.研究发现Fe(110)表面对CO的吸引力大于H2,且预先吸附的CO能阻碍H2的解离,减弱H与Fe之间的作用力.态密度分析结果表明CO中的C原子与Fe原子有多个共轭峰,有强烈的共轭杂化作用.不同应变Fe(110)表面的吸附结果表明CO在Fe(110)表面的吸附能比H2更负,CO与表面的结合强度更大,CO优先吸附.结合热力学定量计算分析CO分压对氢覆盖度影响,结果表明随着CO的分压升高,氢覆盖度降低.表面拉应变越大,需要的CO分压越高.拉应变使得H2,CO吸附能差减小,CO阻碍氢吸附的能力降低是拉应变表面需要更高CO分压的原因.In this work,the competitive adsorption behavior of H2 and CO on strained Fe(110)are investigated by the first-principles method based on the spin-polarized density functional theory to study the hydrogen embrittlement of steels.The results show that the most stable adsorption site for CO is top site,and the orbital of CO molecule hybridizing with Fe3p and 4s states illustrates a strong electronic interaction between them.The adsorption energy values of CO at the four calculated adsorption sites are more negative than those of H2,which favors the binding with Fe(110)surface.The potential energy variations for CO and H2 molecules close to the surface are calculated.The attractive force of the Fe(110)surface acting on CO in 1.5–3?is greater than that acting on H2.The pre-adsorbed CO increases the dissociation energy barrier of H2 from 0.08 eV to 0.13 eV but reduces the force between H2 and surface.The surface tensile strain enhances the interaction between hydrogen and Fe(110),which,however,is reduced by the compressive strain.The opposite tendency is found in the adsorption of CO.The binding strength of CO is stronger than that of H2 on the strained Fe(110)surface.The difference in adsorption energy between CO and H2 decreases with tensile strain increasing.The effect of surface strain and partial pressure of CO gas phase on the surface coverage ratio of H atom are also calculated quantitatively based on thermodynamics at 298 K,with the partial pressure of H2 set to be 10 MPa.The surface ratio of the H atom decreases with partial pressure of CO increasing.The hydrogen coverage drops nearly to zero when the partial pressure of CO reaches a certain value.This result reveals that CO can inhibit hydrogen adsorption on Fe surface.In the case where the surface ratio of hydrogen decreases to 1%,the corresponding CO partial pressures are 105 Pa,1.1×10^3 Pa,2.4×10^5 Pa on–2%,0,2%strained Fe(110)surface,respectively.High CO partial pressure is needed to suppress the hydrogen adsorption since the binding strength of CO

关 键 词：氢脆 竞争吸附 氢吸附 

分 类 号：O647.3[理学—物理化学]