A fuel cell is a device that allows electricity to be obtained directly from certain substances, such as hydrogen or methane, through a chemical reaction called electrolysis. Each cell contains two electrodes, one positive (anode) and one negative (cathode), and the electrolyte that carries the charged particles from one electrode to the other. There is also a catalyst that accelerates the reaction near the electrodes. Cells that use hydrogen react with oxygen and generate water as a "waste" product, so they are very useful in those high-tech applications where a clean source of energy is needed. To understand how a fuel cell or cell works, you can build one with commonly used materials.
Steps
Part 1 of 2: Building the Fuel Cell
Step 1. Gather all the necessary materials
To build a simple home fuel cell you will need 12 inches of platinum or metal coated electrical wire, a popsicle stick, a 9 volt battery with a connector, clear tape, a glass of water, salt (optional) and a voltmeter.
You can purchase the 9-volt battery and battery clip at an electronics store or hardware store
Step 2. Cut the platinum wire into two 15cm segments
You will need to buy it at an electronics supply store, as this metal is not used for normal electrical wiring. Platinum is the catalyst for this reaction.
- Platinum cables are recommended because other materials, such as copper, react with oxygen and salt, polluting the solution with the by-products of the reaction itself.
- You can also use very high quality stainless steel cables, because it doesn't react as quickly.
Step 3. Wrap each wire around a thin metal rod to give it a spring shape
The two springs thus obtained will be the electrodes of the fuel cell. Take the end of the cable and wrap it very tightly around the rod to form a coil. Remove the first thread and repeat the process with the second.
The metal rod can be a nail, a reamer, a metal hanger or the terminal of a multimeter
Step 4. Cut the battery connector terminals in half
Divide both cables attached to the clip and peel off the sheathing using a wire cutter.
Use the stripping part of the pliers to remove the insulation from one end of the cut cables. Strip only the ends of the terminals you cut from the connector
Step 5. Connect the exposed wires to the electrode coils
This way you can attach the electrodes to the voltmeter and the power source (the 9 volt battery) through the clip, to measure how much electricity the fuel cell generates.
- Twist the red terminal wire of the clip around the end of a spiral leaving most of the spiral free.
- Wrap the black terminal wire around the end of the second spiral.
Step 6. Secure the electrodes to a popsicle stick or wooden pin using tape
The stick should be longer than the opening of the container filled with water, so that it can rest on the edges. Secure the electrodes so that they hang down, away from the stick; all this allows you to easily immerse the electrodes in water.
You can use common duct tape or electrical tape. This is not an important detail as long as the electrodes are well connected to the stick
Step 7. Fill a glass with tap water or a saline solution
To get a good reaction it is necessary that there are electrolytes in the liquid. Distilled water doesn't work, because it has no impurities that can act as electrolytes. Salt and baking soda, dissolved in water, are perfect substances for this purpose.
- Regular tap water is rich in impurities and minerals that can function as electrolytes if you don't have salt on hand.
- Add a tablespoon of salt or baking soda for every 240ml of water. Stir until the substance is completely dissolved.
Step 8. Place the stick on the glass
The coils of the electrodes should be submerged in water for most of their length, except where they are connected to the clip wires. Remember that only platinum should remain in contact with the solution.
If necessary, block the stick with more adhesive so that the electrodes stay in the water
Step 9. Connect the wires leading from the electrodes to the voltmeter or an LED bulb
The voltmeter will show the current generated by the fuel cell once it is activated. Join the red lead to the positive probe of the meter and the black lead to the negative probe.
- You will notice a small potential difference reported by the voltmeter, about 0.01 volts, although the meter can also indicate a value of zero.
- You can connect a small light bulb, such as a flashlight, or an LED diode.
Part 2 of 2: Activating the Fuel Cell
Step 1. Touch the 9 volt battery terminals to the clip for a second or two
The battery only needs to send the initial energy through the cables, so that the hydrogen molecules in the water touch the electrodes and separate from the oxygen. When this happens, you should notice bubbles around the electrodes. This process is called electrolysis.
- Observe the bubbles that form around each of the two electrodes; one will have bubbles of hydrogen and the other of oxygen.
- The battery does not have to be perfectly connected to the clip, a short contact is enough to trigger the reaction.
Step 2. Disconnect the battery
Its purpose is only to initiate electrolysis. The separated hydrogen and oxygen will recombine in water releasing the energy they initially used in the form of electricity. The platinum of which the spirals are composed acts as a catalyst to accelerate the process of meeting between the two gases, so that they return to form water molecules.
Step 3. Read the data on the voltmeter display
At first the value may be high, about two volts, but the potential difference will decrease as the hydrogen bubbles dissipate, at first quickly and then more gradually until the last bubble bursts.
The bulb or LED may emit bright light at first, but the intensity will gradually decrease and eventually go out
Advice
- A single fuel cell produces only a small amount of electricity, much like the device described above. Commercially, the cells are assembled in stacks.
- Although the fuel cell discussed in this article uses water as an electrolyte, commercial ones exploit potassium hydroxide (such as those used for the Apollo space program), phosphoric acid, sodium or magnesium carbonate melted at high temperatures or special polymers.
