In-Operando Mapping of pH Distribution in Electrochemical Processes

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Environmental Science

Background:

• pH dynamics are critical in aqueous electrochemical processes, significantly impacting performance.
• Existing methods lack in-operando capabilities for detailed pH monitoring within electrochemical cells.

Purpose of the Study:

• To demonstrate a novel method for in-operando pH distribution monitoring in electrochemical cells.
• To gain new insights into reaction mechanisms in electrocoagulation using this technique.

Main Methods:

• Utilized pH-sensitive fluorescent dyes covering a broad pH range (≈1.5–8.5).
• Employed rapid, electrochemically coupled laser scanning confocal microscopy for dynamic pH visualization.
• Applied to electrocoagulation processes for mechanistic studies.

Main Results:

• Revealed that pH near the aluminum electrode is influenced by current density, cation hydrolysis, and gas evolution.
• Quantified anode pH and gas analysis, identifying hydrogen evolution via a non-Faradaic reaction.
• Demonstrated increased coagulant production linked to anode hydrogen evolution.

Conclusions:

• The developed in-operando pH monitoring method provides unprecedented insights into electrochemical reaction mechanisms.
• This technique can enhance understanding and optimization of various electrochemical applications, including water treatment, electrosynthesis, and batteries.
• The findings suggest new routes to improve electrocoagulation performance through controlled anode reactions.