Is electronegativity a driving force for contact electrification?

Abstract

The microscopic mechanism underlying contact electrification is poorly understood, despite the ubiquity of the phenomenon. Many previous rationalizations have centered on the driver of contact electrification being a difference in electronegativity of the component atoms, such that electrons transfer from the surface with lower electronegativity atoms to the surface with higher electronegativity atoms. Here we use first-principles electron structure calculations to address whether electronegativity can be regarded as a driving force for electron transfer between molecules, and contact electrification more generally. With intentionality, we model simple, highly symmetric systems with systematically varied substituent electronegativities to obtain statistically significant, well-controlled insight into subtle changes in electron distribution. We also apply a variety of charge-partitioning protocols to assess the extent to which the quantification of charge transfer between molecules depends on the chosen (arbitrary) protocol. Our results show that the electron redistribution within interacting molecules does not exhibit a consistent ordering that follows the electronegativities of the component atoms. We therefore conclude that electronegativity-based explanations for contact electrification lack theoretical support.