Copper(II) chloride or what is in italics below
(Copper wire, at least 6 inches
Sodium bicarbonate, 10g
Any source of power that can produce 6-12V at >100 mA )
Zinc strip (approx. 8 mm x 50 mm)
Zinc metal (powder, oxide, strip)
Copper or brass strip (approx. 8 mm x 50 mm), or carbon rod
Hydrochloric acid (concentrated, not less than 10% or 3M, 3 mL)
Sodium chloride, ½g
CAUTION: Do not ingest any of these chemicals. Zinc, copper, sodium bicarbonate, and sodium chloride are not any more than mildly toxic, but they shouldn’t be swallowed. Hydrochloric acid is toxic, and causes burns. Keep off skin, clothes, and metals. Copper hydroxide is an irritant and it is toxic. Copper chloride is a mild oxidizing agent. It should not be allowed to contact metals; it will corrode them. It can cause burns. Zinc chloride is poisonous. Get medical attention if swallowed. Keep off skin.
There are two ways to start. Either dissolve copper(II) chloride in water until the solution is bright green or do the following process in italics. (Dissolve the sodium bicarbonate in approximately 200 mL of water. Cut the copper wire into two equal pieces. Connect the positive and negative ends of the power source to the copper wires. Put them in the solution. Blue copper hydroxide will be produced. Periodically scrape it off. Some of it will be converted to black copper oxide. Allow it to run until the copper wire producing the blue substance gets thin. Then reverse the polarity. Allow it to run again, scraping periodically, until that wire gets thin. Filter the solution through a tissue. Collect the blue-black substance. You may discard the wire and the solution. Dissolve a pea-sized amount in about 8 drops of hydrochloric acid. A green solution (copper chloride) will form. Keep adding copper hydroxide (the blue substance) until no more will dissolve. Put this aside for now.)
Add 8 drops of hydrochloric acid to another container and dissolve as much zinc in it as you can. There should be some residue of zinc. Put this (zinc chloride) aside for now.
Dissolve the sodium chloride in water, and put it aside.
Fold tissues four times, and cut rectangles approximately ¾ in. x 1 ¾ in. out. Make two of these. Cut another rectangle approximately 1 in. x 2 in. out.
On one of the smaller ones, put enough green copper chloride solution to dampen, not wet, the paper. Apply it to both sides sparingly.
On the bigger one, dampen it with the sodium chloride solution.
On the second smaller one, apply the zinc chloride solution sparingly. Put them on a tissue to protect the working surface. The chemicals should not leak out or you have made the tissues.
Sand the metal electrodes so that they are shiny and conductive. Roll the copper chloride paper around the copper strip (or carbon rod). Roll the sodium chloride paper around the copper chloride paper. Roll the zinc chloride paper around the sodium chloride paper. Place the zinc on the zinc chloride paper, and twist-tie the whole assembly together. You may wrap the cell in plastic wrap to prevent evaporation of chemicals. Otherwise, they will evaporate quickly. This cell can produce from 0.7V to 0.9V for the copper strip (1.1V to 1.5V for the carbon rod) at 50 to 400 mA. It may or may not run a small motor (try to get one that can run on 3V or lower). Light bulbs typically run dimly. Wire three or four cells if using the copper electrode (or two cells if using the carbon anode) in series to run an LED. The reaction going on is: Copper chloride + zinc à zinc chloride + copper. You will notice copper crystals growing in the paper if you run the cell. The zinc will start corroding. The green copper chloride will start becoming colorless. Copper may be deposited on the copper strip (or carbon rod). When the green chemical disappears from under the brass or copper strip and is replaced by copper crystals, the battery is dead. Add a couple of drops of green copper chloride to the area that contacts the copper strip to recharge the cell. If the green color leaks to the zinc strip, the cell’s capacity will be limited. A diagram of the cell is below:
There are several ways to increase the capacity.
- 1. Decrease the leakage of the chemicals to each other by making the NaCl sheet thicker.
- 2. Increase the concentration of the zinc chloride, copper chloride, and/or sodium chloride by using more concentrated HCl or dissolving more in the water, respectively.
- 3. Use a tying method so that the zinc and copper strip contacts the papers better.
- 4. Using a less active metal (Ag instead of Cu) and/or a more powerful oxidizing agent at the cathode(AgNO3, NaClO, H2O2, KMnO4, MnO2 instead of CuCl2) may increase the capacity.
- 5. Using a more active metal Mg or Al instead of Zn) and/or a more powerful reducing agent at the anode may increase the capacity.
- 6. Increase the size of the electrodes so that they contact the electrolyte more.
- 7. Increase the size of the electrolyte papers.
If you use methods 7, 6, or 3, you might increase the current. If you use methods 2, 4, and 5, you might increase the voltage. If you use method 1, you might increase the voltage and the current.