Study of the mechanisms of contact electrification and charge transfer between polytetrafluoroethylene and metals

The contact electrification between polytetrafluoroethylene (PTFE) and metals (Al and Cu) is investigated, revealing that much more surface charge is generated in the Al/PTFE system than in the Cu/PTFE system, which is further demonstrated and systematically explained by density functional theory calculations. The charge is believed to firstly transfer to the C atoms and then partof it migrates to nearest F atoms. And the charge transfer at the interface is found to be closely related to the difference in the electronic attraction of the two surfaces in contact, rather than the potential barrier at the interface. Further investigation indicates that electrons transfer from the high energy state of the Al surface to the highest occupied molecular orbit (HOMO) of PTFE and then reach an equilibrium state in the PTFE/Al system, while in the PTFE/Cu system, the electrons of the Cu may transfer to both the HOMO and the lowest unoccupied molecular orbit of PTFE, which indicates a different mechanism of charge transfer. The findings advance our understanding of the contact electrification and charge transfer mechanism between metals and polymers, and sheds light on the material design and modification of contact- or tribo-electrification and other applications. (paper)