铝电解PFCs生成过程:F在炭阳极上吸附实验与第一性原理研究

PFCs formation process in aluminum electrolysis:experiment and First-principles study on adsorption of F on graphene

通过对氟化物熔盐的电解,利用X线光电子能谱分析(XPS)和第一性原理对阳极表面反应层进行表征和计算,研究铝电解熔盐中的F在石墨表面的吸附行为,并指出F在不同石墨烯表面的最可能吸附位点,初步揭示阳极表面全氟化碳气体(PFCs)的微观形成机理。研究结果表明:电解后的阳极表面存在不同结构形式的C—F键,证明C和F在放电期间形成了中间产物CFx。F在本征石墨表面的最稳定吸附位为顶位,而覆盖度的不同并不影响稳定吸附位置。当F吸附在单空位缺陷石墨表面时,最稳定吸附位集中在距离单空位缺陷中心最近的3个C原子周围,包括3个顶位、6个桥位和空穴位。F在本征石墨烯和单空位缺陷石墨烯的吸附均属于化学吸附,并且缺陷可以促进F的吸附。

Through the electrolysis of fluoride molten salt,X-ray photoelectron spectroscopy(XPS)and first principles calculation were applied to characterize and calculate the anode surface reaction layer.The adsorption behavior of F in aluminum electrolysis molten salt on the graphite surface was studied.The most likely adsorption sites of F on different graphene surfaces,and the microscopic formation mechanism of perfluorocarbon gas(PFC)on the anode surface were revealed.The results show that there are C—F bonds with different structures on the anode surface after electrolysis,which proves that C and F form intermediate products CFxduring discharge.The most stable adsorption position of F on the intrinsic graphite surface is the top position,and the different coverage of graphite layers does not affect the stable adsorption position.When F is adsorbed on the surface of singlevacancy defect graphite,the most stable adsorption sites are concentrated around the three C atoms closest to the single-vacancy defect center,including three top sites,six bridge sites and vacancy sites.In addition,the adsorption of F on intrinsic graphene and single-vacancy defect graphene is chemical adsorption,and defects can promote the adsorption of F.