Xu Cheng, Zhang Binbin, Wang Aurelia Chi, Zou Haiyang, Liu Guanlin, Ding Wenbo, Wu Changsheng, Ma Ming, Feng Peizhong, Lin Zhiqun, Wang Zhong Lin
Beijing Institute of Nanoenergy and Nanosystems , Chinese Academy of Sciences , Beijing 100083 , China.
School of Materials Science and Engineering , China University of Mining and Technology , Xuzhou 221116 , China.
ACS Nano. 2019 Feb 26;13(2):2034-2041. doi: 10.1021/acsnano.8b08533. Epub 2019 Feb 5.
It is known that contact-electrification (or triboelectrification) usually occurs between two different materials, which could be explained by several models for different materials systems ( Adv. Mater. 2018, 30, 1706790; Adv. Mater. 2018, 30, 1803968). But contact between two pieces of the chemically same material could also result in electrostatic charges, although the charge density is rather low, which is hard to understand from a physics point of view. In this paper, by preparing a contact-separation mode triboelectric nanogenerator using two pieces of an identical material, the direction of charge transfer during contact-electrification is studied regarding its dependence on curvatures of the sample surfaces. For materials such as polytetrafluoroethylene, fluorinated ethylene propylene, Kapton, polyester, and nylon, the positive curvature surfaces are net negatively charged, while the negative curvature surfaces tend to be net positively charged. Further verification of the above-mentioned trends was obtained under vacuum (∼1 Pa) and higher temperature (≤358 K) conditions. Based on the received data acquired for gentle contacting cases, we propose a curvature-dependent charge transfer model by introducing curvature-induced energy shifts of the surface states. However, this model is subject to be revised if the mutual contact mode turns into a sliding mode or more complicated hard-pressed contact mode, in which a rigorous contact between the two pieces of the same material could result in nanoscale damage/fracture and possible species transfer. Our study provides a primitive step toward understanding the basics of contact-electrification.
众所周知，接触起电（或摩擦起电）通常发生在两种不同材料之间，这可以用针对不同材料体系的几种模型来解释（《先进材料》2018年，第30卷，1706790；《先进材料》2018年，第30卷，1803968）。但是两块化学性质相同的材料之间的接触也可能产生静电荷，尽管电荷密度相当低，从物理学角度来看这很难理解。在本文中，通过使用两块相同材料制备接触 - 分离模式摩擦纳米发电机，研究了接触起电过程中电荷转移方向对样品表面曲率的依赖性。对于聚四氟乙烯、氟化乙丙烯、聚酰亚胺、聚酯和尼龙等材料，正曲率表面带净负电荷，而负曲率表面往往带净正电荷。在真空（约1 Pa）和较高温度（≤358 K）条件下对上述趋势进行了进一步验证。基于温和接触情况下获取的数据，我们通过引入表面态的曲率诱导能量偏移提出了一个曲率相关的电荷转移模型。然而，如果相互接触模式变为滑动模式或更复杂的硬压接触模式，该模型可能需要修正，因为在这种情况下，两块相同材料之间的紧密接触可能会导致纳米级损伤/断裂以及可能的物质转移。我们的研究为理解接触起电的基本原理迈出了初步的一步。
