An electrochemical "cell" is the set up used for electroplating or other electrochemical processes. This usually consists of a beaker
, electrodes, and ionic solution
There are three general electrodes:
The Working Electrode:
This is the electrode or substance that will be plated on to if you are electroplating
. These electrodes are almost always made of metal, though doped
nonmetals can be plated as well.
The Counter Electrode:
This electrode provides the current of electricity that reduces (or oxidizes) the ions of the desired plating material from it's ionic
form so that it will bond to the Working electrode
. These are always metals, a very commonly used being Chromel
The Reference Electrode:
This simply monitors the reaction
taking place in your cell. When hooked to the proper equipment
it helps you know the current density and other things about your cell at any given time. A general use for it is a coulombmeter
. A coulomb
is the amount of charge in one mole of electrons, so if you show one coulomb of transfered electrons on the coulombeter, that signifies that (if for instance, your material was Ni2+
) you have reduced
.5 moles of Nickel
, as it takes 2 moles of electrons to reduce ONE mole
of nickel. In laymans terms, this tells you if what you are doing is working, and if not, it can help you derive
Now that we've covered the types of electrodes, let's walk through a simple cell. Let's say you have a 500ml beaker of the following solution
.3M HBO3 (Boric Acid to keep the pH low)
.2M NiCl (Nickel Chloride to be ionized and used as a nickel source for plating)
.45M NaCl (Sodium Chloride, to be ionized in solution and to help provide ions for electrical flow)
Your electrodes will be:
A copper square, well polished, connected to a copper wire for the working electrode ( to be plated with nickel)
A Chromel counter electrode to provide the charge for the plating)
And a SCE reference electrode (Saturated Calomel Electrode, a mercury rod in KCl solution for monitoring)
Now that you have everything, we're ready to plate.
Set up the electrodes in the solution and hook both the working and counter to a power
source, and the reference
to a monitoring device. Make sure the reference is BETWEEN the counter and working as this placement gives you the best readings.
Give the electrodes the proper amount of current
flow. For this specific operation, that's about 800 millivolts
. This number is arrived at using a Cyclic Volatmeter
Monitor your plating and remove when desired. This specific plating runs at about .2 Coulombs per minute, so your film will only be nanometers thick, even after a day or so.
You have now completed a basic electroplating
with your very own electrochemical cell. Congratulations.