The Overlapped Electron‐Cloud Model for Electron Transfer in Contact Electrification

Abstract

Contact electrification (CE) is one of the oldest topics in physics, which has been discussed for more than 2600 years. Recently, an overlapped electron‐cloud (OEC) model was proposed by Wang to explain all types of CE phenomena for general materials in which a deep overlapping of electron clouds belonging to two atoms results in a lowered potential barrier for electron transfer from one to the other by applying a compressive force, which is simply referred to as Wang transition for CE. Here, the degree of electron‐cloud overlap between two atoms is controlled by using tapping mode atomic force microscopy. A temperature difference and electric field are applied between atoms of two surfaces. It is found that electron transfer only occurs when the contact tip and sample interact in the repulsive‐force region, which corresponds to a strong overlap of the electron clouds. Such a fact even preserves if the tip is at a higher temperature than the sample for 120 K. Alternatively, by applying a bias, electron tunneling would occur when the tip is in the attractive‐force region within which normal electron transfer would not occur. These studies solidify the overlapped electron‐cloud model first proposed by Wang. Further, the temperature and bias effects on the CE are explained based on a modified OEC model.

Universal Triboelectric Nanogenerator Simulation Based on Dynamic Finite Element Method Model

“…Various models for TENGs have been proposed and explored to explain the charge transfer process during the contact of two tribo-materials (i.e., the contact electrification) such as electron-cloud model [ 13 , 14 , 15 ], ion-transfer model [ 16 ], material-transfer model [ 17 ], etc. No matter which model is applied, a constant surface charge density is always assumed to quantitatively represent the transferred charges remaining on the surfaces of the tribo-materials, even after contact electrification.…”

Triboelectric nanogenerators: Fundamental physics and potential applications

“…Recently, the interatomic interaction model was confirmed by using tapping mode atomic force microcopy (AFM) to control the degree of electro-cloud overlap between two atoms [25]. The tapping mode AFM and the illustration of attractive region and repulsive region on the sample surface are displayed in Fig.…”

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“…The distance between two atoms where CE occurs is explored by measuring the surface potential using KPFM in a tapping mode ( Li et al., 2016 ; Lin et al., 2020a ). The surface potential difference between the center of scanned region and the edge after the second KPFM scan is presented in Figure 2 .…”