Role of Surface Functional Groups in Reactive Species Generation at the Water-Solid Interface Under Contact Electrification

Abstract

Water-solid contact electrification (CE) is a common physical phenomenon. The electron transfer during water-solid CE can mediate the redox reactions at the interface, however, the effect of different surface functional groups on this physicochemical process and its mechanism are limited in understanding. Here, we have regulated the redox reactions caused by CE between water and florine-doped tin oxide (FTO) with various functional groups, as well as their electron transfer processes during the contact. It is revealed that the -COOH FTO sample has a larger work function than the no functional group FTO and -OH FTO samples and can easily accept electrons to promote electron transfer from water-solid heterojunctions in CE by density functional calculation. The nitrate reduction and nitrite oxidation experiments showed that the redox capacity of the water – FTO heterojunction with -COOH is much more than that of the water – FTO heterojunction with -OH or fewer functional groups in the CE process. The redox capacity of the water-FTO CE originates from reduction and oxidation species, which was confirmed by the electron transfer and active species detection analysis. These findings deepen our understanding of the correlation between surface functional groups and redox capacity in the CE process.