Origins of Liquid-Solid Contact Electrification

Interfaces between liquid-solid (L-S) are the most important surface science in chemistry, catalysis, energy, and even biology. The formation of electric double layer (EDL) at the L-S interface has been attributed due to the adsorption of a layer of ions at the solid surface, which causes the ions in the liquid to redistribute. Although the existence of a layer of charges on a solid surface is always assumed, but the origin of the charges is not extensively explored. Recent studies of contact electrification (CE) between liquid and solid suggest that electron transfer plays a dominant role at the initial stage for forming the charge layer at the L-S interface. In this chapter, we review the methods for studying the liquid-solid CE, and the recent works about the electron transfer in liquid-solid CE, including sceneries such as liquid insulator, liquid semiconductor, and liquid metal are summarized. Furthermore, the formation about the EDL is revisited with considering the existence of electron transfer at the L-S interface.