Dynamics of electron transfer and coupling between charging and discharging in triboelectrification between insulators

Although triboelectrification (TE) is essential in many industrial and scientific fields, its charge transfer mechanisms are still not fully understood. In this paper, the charging-induced electric potential on the friction surface and the discharging-induced light emission from the contact region during sliding frictions between insulators have been observed simultaneously. The results show that, in the absence of discharging, the temporal variations of surface potential at all the contact points are almost the same, experiencing a rapid growth in the initial stage, followed by a slow growth, and eventually reaching a stable value. To explain such a dynamics of electron transfer, a theoretical expression for the temporal evolution of the surface potential during TE process is proposed by considering the electron transfer as the charging process of a capacitor formed by contacting surfaces, and is found consistent with the experimental measurements. The experiments further indicate that, when discharging occurs, it has no influence on the charging process of the initially negatively charged surface, but can greatly change the charging of the initially positively charged surface, on which the potential will increase initially, soon begin to decrease, and eventually reach a stable value. Such a significant difference in the potential variation when discharging occurs can be attributed to the huge difference in mass between electrons and positive ions produced in the discharging process. The present work may offer a new perspective for understanding the electron transfer dynamics in TE and may provide potential applications in numerous fields involving TE.