Bipolar charge transfer induced by water: experimental and first-principles studies

Area of Science:

• Surface science
• Tribology
• Materials science

Background:

• Bipolar charge distribution in triboelectrification is not well understood.
• Water's role in triboelectrification is complex, acting as both promoter and inhibitor.

Purpose of the Study:

• To investigate the mechanism of bipolar charge distribution in triboelectrification.
• To explore the influence of water on charge transfer polarity and distribution.
• To elucidate the role of surface states and dangling bonds in silicon nitride triboelectrification.

Main Methods:

• Triboelectrification experiments using Kelvin probe force microscopy (KPFM) between an Au/Cr-coated tip and Si3N2 film.
• First-principles calculations to model water-surface interactions and charge transfer.
• Controlled manipulation of frictional conditions to study charge distribution.

Main Results:

• Water can reverse charge transfer polarity and induce bipolar charge distribution on Si3N2.
• Water molecule dissociation on the Si3N2 surface was predicted.
• Dangling bonds and surface states of Si3N2 were identified as crucial for bipolar charge transfer.

Conclusions:

• Water plays a significant role in modulating triboelectrification, including polarity reversal and bipolar charge transfer.
• Surface properties, specifically dangling bonds and surface states, are fundamental to understanding bipolar charge transfer in Si3N2.
• This study provides mechanistic insights into water-induced effects in triboelectric phenomena.