Hello Michael,

I guess some factors will depend on the application (expected currents, scan rate if performing voltammetric methods, concentration of supporting electrolyte, possible interaction of reference electrode ions- for example Cl ions in SCE and any interaction of byproducts).  If you can provide further information regarding your application I may be able to tailor my answer better. Generally speaking, the aim is to stabilise all other parameters such that the reaction at the WE can be accurately observed with reproducible results.

Some general points, for extremely low currents you may consider combining the RE and CE. Or you may wish to use a pseudo-RE if you plan to miniaturise the device (I am currently working with microfabricated devices). Often you wish to reduce errors due to solution resistance - particularly with high currents, and whilst these can often be electronically compensated, it is good practice to minimise the distance between all three electrodes, particularly that of the RE and WE. Often people oversize the CE, maximising the surface area to ensure that it does limit the other half-reaction at the WE but I have found people can sometimes take this too far. Again, maintaining the distances between the electrodes is important so many people use Teflon jigs to hold the electrodes in similar positions to improve reproducibility. The geometry of the electrochemical cell can also be improved to gain other advantages such as anoxic conditions.

There is an old book: "Electrochemical Cell Design and Optimization Procedures" [ISBN: 978-3527102174] that I have not read, but given the title I imagine it covers some important aspects.

Often considered the 'bible' of electrochemistry: "Electrochemical Methods, Fundamentals and Applications" by Allen J. Bard and Larry R. Faulkner, should have some information that may assist you (warning, it is 850 pages long).

Solartron Analytical have a short technical report that covers some basics: "Understanding Electrochemical Cells - Technical Report 17"

I'm not sure if it actually covers electrochemical cell design, but my favourite electrochemical book is a primer written by A. C. Fisher titled  "Electrode Dynamics" and it serves as a fantastic resource to remind yourself of the important processes occurring within the electrochemical cell that could aid you in your design.

On a different note, it is quite common now to use FEA software such as COMSOL to model changes in design for optimization. I find it particularly useful when combining microfluidics, heat transfer, solution mixing, etc.

Hope this help.

Hi Jules,

Thank you for the detailed answer. I will look up those books, and if not too expensive maybe purchase one or two of them. I am making a sensor to detect low concentrations of glucose; the voltage I'm using is 0.2 and I'm getting currents in the 1-20 uA range. What is the advantage of combining the RE and CE? What kind of work are you doing? Are you finishing soon?

Thanks, 

Mike

Hello Michael,

The advantages of combining the CE and RE are specific to application. The RE is usually a high-impedance arrangement to minimise polarisation error. If the currents are very small then this can be negligible. 

Combining both the CE and RE minimises the electronics - useful if you want to make simple, low-cost devices.

There are errors associated with REs that are often overlooked (for instance frits in SCEs can often become blocked, Cl ions from Ag/AgCl REs can interact with the cell, etc.) so in a few applications removing the RE can surprisingly improve performance.

I have contacted you directly in case I can help you further.