Choosing Working, Reference and Counter Electrodes

Jump to: Three-Electrode Set Up | Working Electrode | Reference Electrode | Counter Electrode | Electrode Body | Other Considerations

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Choosing the right electrodes is an important part of innovative electrochemical research. There are several factors to consider when choosing which electrode is best for your application.

Before choosing an electrode, you should fully consider and outline the expected experimental conditions, such as electrolyte choice, pH, and required potential range, and their effects on the electrochemical reaction. Once these are decided, you will need to choose the appropriate material, electrode geometry and electrode body to suit your experimental parameters.

While there are some common requirements, working, counter and reference electrodes all require slightly different things. For example, in working and counter electrodes, you must consider the material’s specific potential window, sometimes referred to as its “safe zone”. These are the potential limitations where the electrode won’t experience oxidation, reduction, or degradation.

Please note that the following electrode suggestions are only for laboratory electrochemistry experiments.

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Three Electrode Electrochemical Cell Set-Up

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To get reliable and repeatable data, it’s always encouraged to conduct your electrochemistry experiments using a three-electrode set up. This consists of:

• A Working Electrode (WE) where the electrochemical reaction of interest occurs.
• A Reference Electrode (RE) that provides a stable, known potential against which the WE is measured.
• A Working Electrode (WE) which completes the circuit, allowing current to flow without passing significant current through the RE.

These are suspended within an electrochemical cell, with each electrode connected to a potentiostat.

Important things to bear in mind:

• No significant current should pass through the reference electrode, as this would polarise it and lead to potential drift.
• Where possible, the electrodes should be housed in separate compartments, connected via a glass frit or membrane separator. This is particularly important for high-precision experiments or electrocatalysis studies, where cross-contamination or product crossover can significantly affect results.
• The reference electrode should always be housed in a separate compartment.

Choosing a Working Electrode

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The working electrode is arguably the most important feature of an electrochemistry set-up, as it is the site where the measured reaction takes place. Selecting the right electrode for your experiment is key to reliable and accurate electrochemistry measurements.

Electrode Material

Glassy Carbon (GC), Platinum (Pt), and Gold (Au) are the most common working electrode materials. The benefits and limitations of each material are listed in the table below.

Glassy Carbon	Platinum (Pt)	Gold (Au)
High potential window	Excellent electrical conductivity	Chemically stable & conductive metal
Low intrinsic catalytic activity	Fast electron transfer kinetics	High selectivity and affinity
Highly inert	Highly resistive for a metal. Stable under most hostile environments (acids, high temp, various solvents)	Most common choice for CO2 reduction studies
Low cost (compared to platinum)	High catalytic activity in some situation
Robust – will degrade in hot concentrated acid	Unsuitable for HER & ORR reactions
Most common choice for standard electrochemical experiments	Most common choice for measuring for experiments with fast electron transfer kinetics

Stationary vs Rotating Disk Electrode

Most experiments only require stationary working electrodes. However, rotating disk or rotating ring disc electrodes allow for higher control over reactant transfer, facilitating more interesting studies.

Working Electrode Designs

Working electrodes can have different shapes and geometries. Different geometries have different advantages and can be used for different purposes.

Standard Electrode

L-Shaped Electrode

Electrode Holders

Detachable Holders

Choosing a Reference Electrode

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The reference electrode provides the stable, consistent potential that the WE potential is measured against. It is in a separated half-cell with a well-defined chemical equilibrium that remains unchanged under controlled conditions.

Pseudo-reference electrodes (e.g. Ag wire)

You can also use a pseudo-reference electrodes (such as Ag wire) which make direct contact with the bulk electrolyte itself. These require calibration with a known internal standard such as ferrocene. One of the advantages of these referecence are they don't need a seperated half cell. However, these can be subject to contamination issues. Also it can be difficult to keep the reaction seperate and unaffected by the reaction in the bulk electrolyte, which can lead to some issues.

Choosing a Counter Electrode

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A counter electrode, or auxillary electrode, must be highly conductive with low charge-transfer resistance, and excellent chemical stability across various pH ranges.

Counter Electrode Materials

The benefits and limitations of the Ossila Counter Electrode materials are listed in the table below.

Platinum	Graphite
Excellent conductivity	Highly conductive
Highly inert and thermally stable	Relatively inert and high thermal stability
Resistance to oxidation	Good alternative where platinum would lead to Pt poisoning e.g. HER studies.
Wide potential range	Low cost alternative to platinum
Industry standard for EC experiments	Subject to oxidation, particle shredding and corrosion.
Can lead to Pt poisoning in certain reactions e.g. HER/ORR/CO2RR studies*	Good alternative where platinum would lead to Pt poisoning e.g. HER studies.
	More limited potential range than platinum and not for use in harsh conditions.

*Platinum working electrodes can be used for these studies when used in with H-Cell.

For certain applications, alternative counter electrode materials such as stainless steel or titanium can offer improved mechanical durability or compatibility with specific electrolytes.

However, with all counter electrodes it is important to consider their electrochemical behaviour such as surface oxidation, passivation, or corrosion under certain potentials.

Counter Electrode Shape

The surface area of a counter electrode should be roughly 10 x the area of the working electrode to assure any counter electrode surface effects won’t be the limiting factor of the reaction. This is known as the 10:1 rule.

Electrodes with different shapes offer increased surface area. Different counter electrode geometries offer distinct advantages depending on the application:

Wire

Coil

Plate

Mesh

Electrode Body

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The main requirement of the electrode body is that it is as stable, inert and insulating as possible (while not increasing costs too much).

PTFE is a common choice as it is almost totally chemically inert and an excellent electrical insulator, making it preferable for harsh chemical environments. However, PEEK electrodes offer superior mechanical strength, hardness, and thermal stability. The best choice depends on your experiment's specific chemical, mechanical, thermal, and electrical requirements.

Electrode Considerations

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• Never use a Pt counter electrode in the same compartment as a non-noble HER catalyst (like MoS₂ or NiFe). Trace Pt will dissolve and deposit on your catalyst, making a mediocre material look like a world-record performer.
• Avoid using low-density graphite rods in high-current alkaline studies. The graphite can exfoliate, releasing micro-particles that physically coat your working electrode and invalidate your surface area measurements.
• Glass frits are porous and "trap" ions. If you move a fritted counter-electrode assembly from a concentrated acid to a neutral buffer without extensive soaking in ultra-pure water, you will contaminate your new electrolyte.
• Do not assume "Inert" means "Invincible." Even Platinum can form surface oxides or hydrides that change its catalytic behaviour over long-duration experiments.