Transpassive Metal Dissolution vs. Oxygen Evolution Reaction: Implication for Alloy Stability and Electrocatalysis.

Area of Science:

• Materials Science
• Electrochemistry
• Corrosion Science

Background:

• Multi-principal element alloys (MPEAs) offer tunable properties for electrochemical applications.
• Their stability across various pH ranges is a key advantage.
• However, their behavior under specific reaction conditions requires detailed investigation.

Purpose of the Study:

• To investigate the concurrent occurrence of metal dissolution and oxygen evolution reaction (OER) in an equimolar CrCoNi alloy.
• To develop and apply a characterization scheme to differentiate OER contributions from alloy dissolution.
• To understand the mechanism of transpassive metal dissolution in MPEAs.

Main Methods:

• Scanning electrochemical microscopy (SECM) for OER onset detection.
• Inductively coupled-mass spectrometry (ICP-MS) and UV/Vis spectrometry for quantitative metal ion analysis.
• In situ electrochemical atomic force microscopy (EC-AFM) to observe surface morphology changes.

Main Results:

• Significant metal dissolution of CrCoNi alloy was observed during OER in a corrosive electrolyte (0.1 M NaCl, pH 2) in the transpassive region.
• SECM, ICP-MS, and UV/Vis spectrometry successfully delineated OER and alloy dissolution.
• EC-AFM revealed intergranular corrosion as the dominant mechanism for transpassive dissolution.

Conclusions:

• Transpassive dissolution of MPEAs during OER can occur without obvious corrosion indicators.
• Accurate assessment of OER catalysts requires quantification of released metal ions.
• Metal ion release can negatively impact electrolyzer efficiency and reactor component integrity.