Recently, the research on 'Contact Electrification' by Ph.D. Zhang Yanzhen got published by Physical Review X. American Physical Society(APS)  website also reported the finding.

Two identical insulators, despite having no free electrons, are able to charge one another upon contact. This process, called 'contact electrification', is important both in natural phenomena (like lightning near volcanic dust plumes) and in industrial applications (like laser printing). Based on experiments, Zhang and his partners have suggested that, in humid environments with strong electric fields (e.g., thunderstorms), the charge carriers are likely hydronium (H3O+) and hydroxide (OH-) ions, driven by the electric field along water adsorbed on the surfaces of the insulators.

See more about the paper: http://journals.aps.org/prx/abstract/10.1103/PhysRevX.5.011002

Physical Review X (PRX) launched by APS in 2011, is a highly selective, online-only journal. It mainly offers open access for key papers from basic, applied, and interdisciplinary physics. It is committed to disseminate innovative and impactful research advances to the broad science and engineering communities.

Editor: Bu Lingduo

Source: UPC News Center