Mica's Homo-Positive-Charging Behavior Enabled Self-Powered Porous Elastomer for Energy Harvesting in High Humidity

Abstract

Tribo-charges on contact and separation derive from the properties of contacted materials, and are of opposite polarities according to the conventional view. Interestingly, mica, as a representative of a series of inorganic materials, is always positively tribo-charged with two pieces of mica contacted. Similar homo-charging phenomena have also been detected in other inorganic particles, such as NaCl, quartz, and CaF2, which usually occur in mineral flotation and sand dust formation, and contain abundant triboelectric energy. However, it is hard to harvest this disordered and ubiquitous energy and the detailed understanding of this homo-positive-charging behavior at the molecular level remains lacking. Here, we verified the dynamic feature of the homo-positive-charging behavior, and elucidated the underlining mechanism to be the enhanced evaporation of OH(H2O)n－ on mica’s surface. Furthermore, we utilized mica’s homo-positive-charging behavior to prepare a self-powered porous elastomer, realizing an endogenous TENG and an optimized contact-separation mode TENG. The maximum output power density was 55 mW/m2, and 83% original generation was achieved in high humidity of 84.3%. This work contributes to understanding the mica’s tribo-charging behavior, and further provides a generic method to achieve self-powered elastomer, especially in high humidity, which promises wide applications.

Keywords: Mica's homo-positive-charging behavior, Interface, Endogenous triboelectric nanogenerator, High humidity