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 wire.
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 why.
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.
STEP ONE: 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.
STEP TWO: 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.
STEP THREE: 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.