Ion-Specific Modulation of Ferri/Ferrocyanide-Driven Gold Dissolution Uncovered by Quantitative Quartz Crystal...

Area of Science:

• Electrochemistry
• Surface Science
• Materials Science

Background:

• Gold electrodes in ferri/ferro cyanide (FFCN) are commonly used as stable electrochemical benchmark systems.
• However, recent studies indicate drift in measurements, suggesting potential instability.
• The precise mechanisms and influencing factors of this instability remain unclear.

Purpose of the Study:

• To quantify gold mass loss induced by FFCN solutions.
• To investigate the influence of various solution parameters (anion, cation, pH, buffer) and surface modifications (self-assembled monolayers) on gold etching.
• To elucidate the chemical behavior of FFCN on gold surfaces.

Main Methods:

• Utilized quartz crystal microbalance (QCM) to precisely measure gold mass changes.
• Systematically varied supporting electrolyte composition, pH, and buffer systems.
• Investigated the effect of oxygen levels, solution aging, light exposure, and different types of self-assembled monolayers (SAMs).

Main Results:

• FFCN solutions induce measurable gold mass loss, indicating active etching.
• Gold dissolution is significantly tunable by changes in supporting electrolyte, pH, and buffer chemistry.
• Oxygen depletion reduces etching, while solution aging and light exposure increase it.
• Neutral, long, well-packed SAMs attenuate etching, whereas charged or short SAMs accelerate it.

Conclusions:

• FFCN on gold behaves as a chemically active etchant, not an inert probe.
• Electrochemical measurements using FFCN require explicit consideration of gold etching.
• Factors such as salt concentration, pH, buffer type, surface chemistry, and solution handling conditions critically influence FFCN-induced gold dissolution.