Electrolysis is an important part of renewable energy research, and you can do it yourself with household materials! During electrolysis of water, water is split into its two ingredients: hydrogen and oxygen. The pure hydrogen that is produced in this reaction can then be used in fuel cells to generate electricity. A drawback to many types of renewable energy is that the product isn't consistent. Solar power can't produce electricity at night, for example, and often the wind blows more at night than during the day. Electrolysis can help solve these problems: we can use excess solar energy during the day to produce hydrogen for nighttime power, and vice versa for wind power.
Electrolysis is also used for other applications, like electroplating metal. Scroll down for electroplating instructions and Watch our project video to see us copper-plate a key >>
All you need in order to see electrolysis in action is a battery and a couple pencils! (Adult supervision required.)
As soon as you connect the wires to the battery, you will see bubbles appearing around each of the pencil tips in the water and floating upward. Those bubbles are the components of water—hydrogen and oxygen gas—that have been split apart by the electricity as it travels through the water from one pencil to the other. The pencil attached to the negative terminal of the battery collects hydrogen gas while the one connected to the positive terminal collects oxygen. Does one pencil collect more bubbles than the other? Which one? Why do you think this is? (Hint: Water's chemical name is H2O because it has two hydrogen atoms to every one oxygen atom.)
Electrolysis is a key part of renewable energy, but it is also used for other things. Electroplating uses a form of electrolysis in which the electrodes play a bigger role than just conducting the current. Using electricity, you can coat the metal of one electrode with the metal of the other! Jewelry and silverware can be silver- or gold-plated, while zinc is often used to coat iron to protect against rust. Professional electroplating requires specialized chemicals and equipment to make a high-quality coat, but in this project you can try your hand at a simple procedure that will transfer copper to a brass key. (Adult supervision and chemical safety equipment required.)
>> Watch our project video to see this project in action!
The copper sulfate solution is an electrolyte that conducts electricity from one electrode to the other. When the current is flowing, oxidation (loss of electrons) happens at the copper anode, adding copper ions to the solution. Those ions travel on the electric current to the cathode, where reduction (gain of electrons) happens, plating the copper ions onto the key. There were already copper ions present in the copper sulfate solution before you started, but the oxidation reaction at the anode kept replacing them in the solution as they were plated onto the key, keeping the reaction going.
This project has many variables, including the cleanness and smoothness of the key, the strength of the copper sulfate solution, and the strength of the current. If a black soot-like substance starts forming on the key, your solution is not strong enough for the current. Take the electrodes out and add more copper sulfate. When you put them back in, make sure the anode and cathode are as far apart as possible.
There are lots of projects you can do with electroplating! One fun idea is to use a flat piece of brass as your cathode and draw a design on it with an oil-based marker. The copper will not bond where the marker is. After you're done plating it, you can use acetone (or nail-polish remover) to wipe off the marker, leaving a design of the brass showing through the copper. You can use a little metal polish to make the copper shiny, if you want.
You may want to try this simple copper-plating experiment that doesn't use electrolysis and requires only household materials.