Silver Electrodeposition from Ag/AgCl Electrodes: Implications for Nanoscience

With the advancement of nanoscience, silver/silver chloride (Ag/AgCl) electrodes have become widely utilized in microscale and nanoscale fluidic experiments, because of their stability. However, our findings reveal that the dissolution of AgCl from the electrode in Cl^--rich solutions can lead to significant silver contamination, through the formation of silver complexes, ${\left[{AgCl}_{n+1}\right]}^{n-}$. 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.