Polytetrafluoroethylene (PTFE) is a promising negative triboelectric material used in high-performance triboelectric nanogenerators (TENGs). To improve the triboelectric output of PTFE, an understanding of the triboelectric properties and electron transfer factor in PTFE is highly required. However, the triboelectric properties of PTFE have not been analyzed by considering the side effects during TENG operations (e.g., deformation). Here, we investigated the change in the triboelectric properties of PTFE due to molecular structure deformation, which is driven by contact force, using density functional theory (DFT). The deformation of the molecular structure induces modification of the electronic structure and triboelectric properties. Using the linear and deformed PTFE models (80°, 70°, 60°), we determined that the energy of the lowest unoccupied molecular orbital (LUMO) is decreased under deformation using the energy band diagram and density of states (DOS) (linear: 5.831 eV, 80°: 5.358 eV, 70°: 4.028 eV, 60°: 1.729 eV). This implies that the deformation due to the contact force enhances its negative triboelectric property (i.e., electron-accepting property). We analyzed this phenomenon because carbon in the deformation region has a strongly electron-deficient state, and the positive local dipole due to that state is enhanced. In addition, we investigated the LUMO changes, in part, from anti-bonding orbital to a bonding orbital. Because the bonding orbital has a more stable energy state than the anti-bonding orbital, the energy level of the LUMO could be lowered.
|Publication status||Published - 2022 Sept|
Bibliographical noteFunding Information:
This work was financially supported by Basic Science Research Programs ( 2020R1A2B5B01001785 ) and Nano Material Technology Development Program ( 2020M3H4A1A03084600 ) through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT. S,M. Kim acknowledges the support from Insilico in Korea.
Sang-Woo Kim an SKKU Distinguished Professor (SKKU Fellow) at Sungkyunkwan University (SKKU). His recent research interest is focused on triboelectric/piezoelectric nanogenerators, self-powered sensors and body-implantable devices, and 2D materials. Prof. Kim has published over 300 research papers (h-index of 80). He served as Chairman of the 4th NGPT conference at SKKU in 2018. Now he is a PI of Research Leader Program and a Director of the National Core Materials Research Center supported by National Research Foundation of Korea, and is currently serving as an Associate Editor of Nano Energy and an Executive Board Member of Advanced Electronic Materials.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
- Electrical and Electronic Engineering