摘要
针对目前铝电解阳极效应阶段全氟化碳(PFCs)气体排放原因不明的问题,采用密度泛函理论计算与X射线光电子能谱(XPS)检测手段对PFCs的微观形成机理进行研究。计算结果表明,在阳极表面不断放电的过程中,熔盐中含氟配离子[F]−使碳环边缘的C—H键逐渐被C—F键取代,导致芳香族C—C键饱和,随后碳环开环逐渐形成—CF_(3)基团和—C_(2)F_(5)基团,最终脱出CF_(4)和C_(2)F_(6)产物。XPS结果表明,电解后的阳极表面存在不同类型的—CF_(x)结构,验证了量子力学计算中[F]−在碳边缘不断放电、最终形成不同C—F键的可能性。
In view of the unclear cause of perfluorocarbons(PFCs)emission in the anode effect stage of aluminum electrolysis,the microscopic formation mechanism of PFCs was studied by density functional theory calculation and X-ray photoelectron spectroscopy(XPS).It is found that the discharge of fluorine containing anions([F]−)on carbon anode first causes the substitution of C—H by C—F and further results in the saturation of aromatic C—C bonds,leading to the appearance of—CF_(3)or—C_(2)F_(5)group through six-carbon-ring opening.Elimination of—CF_(3)and—C_(2)F_(5) with F atom could be a likely mechanism of CF_(4) and C_(2)F_(6) formation.XPS results confirm that different types of—CF_(x) group can be formed on anode surface during electrolysis,and the possibility that[F]−discharges continuously at the C edge and finally forms different C—F bonds in quantum mechanical calculation was verified.
作者
孙珂娜
李劼
张红亮
李天爽
Ke-na SUN;Jie LI;Hong-liang ZHANG;Tian-shuang LI(School of Metallurgy and Environment,Central South University,Changsha 410083,China;National Engineering Research Center for Low-carbon Nonferrous Metallurgy,Central South University,Changsha 410083,China)
基金
the financial supports from the National Natural Science Foundation of China(Nos.51974373,51874365,62133016)
the Major Scientific and Technological Innovation Projects of Shandong Province,China(No.2019JZZY020123)
the Fundamental Research Funds for the Central Universities of Central South University,China(No.2019zzts242)。
关键词
微观形成机理
铝电解
全氟化碳气体
密度泛函数理论计算
microscopic formation mechanism
aluminum electrolysis
perfluorocarbon gas
density functional theory calculation
