# Charge Transfer Altered by Particle Deposition as a Contact Line Moves over a Hydrophobic Surface

## TL;DR

Moving water over a hydrophobic surface with particles changes how much electric charge is transferred.

## Contribution

The study shows how particle deposition alters charge transfer during slide electrification.

## Key findings

- TiO2 nanoparticles reduce charge transfer exponentially with time.
- Carbon particles initially increase charge transfer before decreasing it.
- Ion release from particles affects charge transfer dynamics.

## Abstract

An aqueous three-phase contact line moving over a hydrophobic
surface
is known to give rise to electrical charge transfer in a process that
is sometimes referred to as slide electrification. Here it is shown
that the charge transfer is significantly altered if the liquid contains
small particles that adhere to the solid surface. For TiO2 nanoparticles in water, it is found that the charge transfer decays
nearly exponentially to a very small value with a time constant that
depends on the particle concentration. The increase in particle area
coverage on the solid surface is correlated to the reduction in charge
transfer, and a simple theory is developed to explain this behavior.
Further studies of two different types of carbon particles in water
reveal that the charge transfer initially increases before decaying
even though the particle area coverage monotonously increases with
time. It is suggested that this behavior is due to the release of
ions, which increase the charge available to be transferred from the
electrical double layer.