Contact electricity was discovered in ancient Greek times. Although its discovery has been more than 2,600 years old, there are still many disputes on its principle. The most important one is that in the electrification process, the charge transfer is via electrons or The transfer of ions to achieve and why the generated charge can remain on the surface of the material for a long time. The contact between the metal and the metal or between the metal and the semiconductor is electrified and is generally considered to have generated electron transfer and can be passed through a work function or contact potential. The difference is explained. By introducing the concept of surface states, electron transfer theory can also explain to some extent the contact electrification between metals and insulators. However, ion transfer can also be used to explain contact electrification, and is more applicable to Electrostatic systems containing polymers, for example, in which ions or functional groups dominate the generation of electrification phenomena. Almost all existing studies relating to contact electrification have focused on the total amount of electric charge generated, but few Real-time detection or temperature-related studies of changes in static electricity. To date, there is no convincing theory that can be used to reveal exposure. The dominant mechanism of electrification originates from electrons or ion transfer.
Academician of the Chinese Academy of Sciences and Chief Scientist of the Institute of Nano Energy and Systems, Chinese Academy of Sciences Wang Zhonglin Based on Maxwell's principle of displacement current, Triboelectric nanogenerator (TENG) technology can accurately characterize the surface charge density and can realize different temperatures. Application, this provides a new way to solve the above-mentioned problems in contact electrification. Recently, under the guidance of Wang Zhonglin, associate professors Xu Cheng, Dr. Ji Yunlong, and Ph.D. student Wang Qi achieved the TENG that can be designed to work at high temperatures. The real-time and quantitative measurement of the surface charge density/charge quantity reveals the charge characteristics and the underlying mechanism during the contact electrification. This study has designed different kinds of TENG and caused TENG to generate only a very small amount of charge during operation. Therefore, we can ignore the influence of the charge generated by itself. By introducing the initial charge, we study the evolution characteristics of the surface charge with time under different temperature conditions. The experimental and simulation results show that it conforms well with the thermal electron emission equation and confirms The main contact between two different solid materials For electron transfer. In addition, the study also revealed that the surface of different materials has different barrier heights. It is precisely because of the existence of this barrier that the charge generated by the contact electrification can be stored on the surface without escape. Based on the above Electron emission dominates the contact electrification mechanism. This study further proposes a universal electron cloud-potential trap model, which for the first time realizes a unified interpretation of the principle of contact electrification between any two conventional materials. The method proposed in this study has It helps to better understand the contact electrification effect and provides a scientific basis for the development of friction nano-generators in micro- and nano-energy, blue energy, self-driven sensing, artificial intelligence, robotics and physics applications.
Relevant research results were published in "Advanced Materials."
(a)-(c) Electron clouds and potential wells (three-dimensional and two-dimensional drawings) of atoms of two different materials in a state before electrification, after electrification and after electrification; (d) at higher levels Discharge status under temperature.
