Quantifying electron-transfer in liquid-solid contact electrification and the formation of electric double-layer

TLDR

Contact electrification has been known for more than 2600 years, yet the nature of charge carriers and their transfer mechanisms, especially in liquid–solid contact electrification, remain poorly understood. The study investigates liquid–solid contact electrification and the decay of surface charges on solids under varying thermal conditions. By applying electron thermionic emission theory, the authors distinguish electron from ion transfer and propose a two‑step model that demonstrates electric double‑layer formation in liquid–solid contact electrification. The results reveal both electron and ion transfer, show that solutes, solution pH, and solid hydrophilicity affect their ratio, and confirm that the proposed two‑step model leads to electric double‑layer formation.

Abstract

Abstract Contact electrification (CE) has been known for more than 2600 years but the nature of charge carriers and their transfer mechanisms still remain poorly understood, especially for the cases of liquid–solid CE. Here, we study the CE between liquids and solids and investigate the decay of CE charges on the solid surfaces after liquid–solid CE at different thermal conditions. The contribution of electron transfer is distinguished from that of ion transfer on the charged surfaces by using the theory of electron thermionic emission. Our study shows that there are both electron transfer and ion transfer in the liquid–solid CE. We reveal that solutes in the solution, pH value of the solution and the hydrophilicity of the solid affect the ratio of electron transfers to ion transfers. Further, we propose a two-step model of electron or/and ion transfer and demonstrate the formation of electric double-layer in liquid–solid CE.