Silver Leakage from Ag/AgCl Reference Electrodes as a Potential Cause of Interference in the Electrocatalytic Hydrogen Evolution Reaction

The electrocatalytic hydrogen evolution reaction (HER) is of considerable interest for the production of H 2 from sustainable sources. Herein, we show that under conditions commonly employed in identifying new electrocatalysts for this reaction (using Ag/AgCl reference electrodes in 1 M H 2 SO 4 ), silver ions can leak from the reference electrode into solution and then deposit on the working electrode as Ag(0), giving current densities for the HER of over 5 mA cm –2 at ∼500 mV overpotential. This is well within the activity range reported for many electrocatalysts of the HER and calls into question the validity of any reports using Ag/AgCl reference electrodes which either fail to explicitly exclude silver as a cause of the electrocatalytic activity or else cannot demonstrate significantly superior activity to this baseline.