Silver Electrodeposition from Ag/AgCl Electrodes: Implications for Nanoscience

TL;DR

This paper investigates silver electrodeposition from Ag/AgCl electrodes in chloride-rich solutions, revealing that AgCl dissolution can cause silver contamination and electrodeposition on graphene, impacting nanofluidic experiments.

Contribution

It uncovers the mechanism of silver electrodeposition from Ag/AgCl electrodes in chloride solutions and its implications for nanoscience experiments.

Findings

AgCl dissolution leads to silver contamination in chloride-rich solutions.

Silver electrodeposition on graphene can occur from Ag/AgCl electrodes.

Electrodeposition explains observed currents previously attributed to ionic flow.

Abstract

With the advancement of nanoscience, silver/silver chloride (Ag/AgCl) electrodes have become widely utilised in microscale and nanoscale fluidic experiments, because of their stability. However, our findings reveal that the dissolution of AgCl from the electrode in \ch{Cl-}-rich solutions can lead to significant silver contamination, through the formation of silver complexes, \ch{[AgCl_{n+1}]^{n-}}. We demonstrate the electrodeposition of silver particles on graphene in KCl aqueous solution, with AgCl dissolution from the electrode as the sole source of silver. This unexpected electrodeposition process offers a more plausible interpretation of the recently reported ``ionic flow-induced current in graphene''. That is, the measured electronic current in graphene is due to the electrodeposition of silver, challenging the previously claimed ``ionic Coulomb drag''. More caution is called for when using Ag/AgCl electrodes in microfluidic, and especially nanofluidic systems, because AgCl dissolution should not be neglected.