Overestimation of photoelectrochemical hydrogen evolution reactivity induced by noble metal impurities dissolved from counter/reference electrodes

A three-electrode system is typically utilized in many voltammetry studies to understand the behavior of an analyte at the electrode/electrolyte interface. A bulk Pt piece is usually used as a counter electrode in such systems because of its high activity and stability in many electrochemical reactions. However, the dissolution of the Pt counter electrode has led to growing concerns about the inaccurate evaluation of the inherent characteristics of the analyte. In the present study, we have demonstrated that strong interferences emerged from the conventional Pt counter and Ag/AgCl reference electrodes in the photoelectrochemical (PEC) hydrogen evolution reaction (HER) with a model photocathode of p-type silicon (p-Si). Under light illumination, the Pt counter electrode is polarized to as high as 1.6–2.0 VRHE, which leads to a non-negligible Pt dissolution from the oxidized surface, as monitored by operando inductively coupled plasma-mass spectrometry (ICP-MS). Post-reaction spectroscopic and microscopic s...