On the material-dependent charge transfer mechanism of the contact electrification

Although contact electrification (CE) has been discovered for more than 2600 years, its dominant charge transfer mechanism by either electrons or materials/ions continues to elude the scientific community. Here, the material dependent CE mechanism with a model established through the extracted potential barrier height W is demonstrated via the contact-separation mode triboelectric nanogenerator as the tool. The results indicate the W in metal/polymer pairs is mainly determined by the polymer rather than the metal, implying the electron transfer dominant mechanism. On the contrary, the W extracted in CE of polymer/polymer pairs may be related to multiple material surfaces and/or other factors such as chemical reactions, indicating the possible co-existence of both electron transfer and material transfer mechanisms. This material-dependent charge transfer mechanism may give a potential answer to the millennium debate on the CE, which is essential for controlling the surface charge level upon requirements of applications.