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Overestimation of Photoelectrochemical Hydrogen Evolution Reactivity Induced by Noble Metal Impurities Dissolved from Counter/Reference Electrodes
journal contribution
posted on 2020-02-25, 15:40 authored by Sang Gu Ji, Haesol Kim, Hojoong Choi, Sanghan Lee, Chang Hyuck ChoiA 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 led to growing concern about 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). Postreaction spectroscopy and microscopy studies
confirm the formation of Pt and Ag particles on p-Si photocathode,
resulting in erroneous overestimation of the HER activity of p-Si.
Various configurations of the three-electrode system, e.g., an H-type
cell with a Nafion membrane, have been studied to find a suitable
cell structure for prohibiting undesirable contamination of p-Si.
Isolation of p-Si from the Pt counter and Ag/AgCl reference electrodes
using the Nafion membrane effectively alleviates the contamination
of p-Si but, toward the end, the metallic ions can be slowly deposited
on p-Si by diffusion through the membrane. Consequently, this work
highlights that the careful caution is necessary when the conventional
Pt counter and Ag/AgCl reference electrodes are employed; it is recommended
to use a graphite counter electrode and separate reference electrode
to prevent artifacts originating from the dissolved Pt and Ag species
during PEC cathode evaluations.
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bulk Pt piecegraphite counter electrodeNafion membraneRHEPt counterthree-electrode systemp-Sihydrogen evolution reactionPhotoelectrochemical Hydrogen Evolution Reactivity InducedreferenceNoble Metal Impurities DissolvedHERPt counter electrodeAgICP-MSnon-negligible Pt dissolutionPEC cathode evaluations
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