Electrolysis is the process in which a chemical reaction is started with electricity (Andersen). This is usually done with liquids and especially with ions dissolved in water. Electrolysis is used widely in today's industry and is a part of the production of many products. The world would be quite a different place without it. No aluminum, no easy way to obtain essential chemicals, and no plated metals. It was first discovered in the 1800s and has developed into the understanding scientists have of it today. In the future, electrolysis might be even more important, and as scientific progress proceeds, scientists will find new and important uses for the process.
Electrolysis of Copper (II) Chloride
How it works
Electrolysis is performed by running direct current through a liquid, usually water. This causes the ions in the water to gain and release charges at the electrodes. The two electrodes are a cathode and an anode. The cathode is the electrode that the cations are attracted to and the anode is the electrode that the anions are attracted to. This makes the cathode the negative electrode and the anode the positive electrode. What happens when voltage is put across the two electrodes, is that the ions in the solution will go to one of the electrodes. The positive ions will go to the cathode and the negative ions will go to the anode. When direct current flows through the system, the electrons will flow out to the cathode. This makes the cathode have a negative charge. The negative charge then attracts the positive cations which will move towards the cathode. At the cathode the cations become reduced, they gain electrons. When the ions gain electrons, they become atoms again and form a compound of the element they are. An example is the electrolysis of copper(II) chloride, CuCl2. Here the copper ions are the positive ions. When current is applied to the solution, they will, therefore, move towards the cathode where they are reduced in the following reaction: Cu2+ + 2e- -> Cu. This will result in a copper plating around the cathode. At the positive anode, the negative chloride ions will gather. Here they will give up their extra electron to the anode and form bonds with themselves, resulting in chlorine gas, Cl2.
History of Electrolysis
Electrolysis was first discovered in the year 1800. After the invention of the voltaic pile by Alessandro Volta the same year, chemists used a battery and placed the poles in a container of water. There they discovered that current flowed and that hydrogen and oxygen appeared at the electrodes. They did the same thing with different solutions of solids, and also here they discovered that current flowed and that the parts of the solid appeared at the electrodes. This astonishing discovery led to further speculations and experiments. Two electrolytic theories emerged. One was based on an idea suggested by Humphrey Davy. He believed that “... what has been called chemical affinity [is] merely the union … of particles in naturally opposite states,” and that “... chemical attractions of particles and electrical attractions of masses [are] owing to one property and governed by one simple law” (Davis 434). The other theory had its basis on the ideas of Jöns Jacob Berzelius, who believed “... that matter consisted of combinations of “electropositive” and “electronegative” substances, classifying the parts by the pole at which they accumulated during electrolysis” (Davis 435). In the end, both of these theories were incorrect, but they did contribute to the current knowledge of electrolysis.
Later, Humphrey Davy's laboratory assistant, Michael Faraday, started doing experiments on electrolysis. He wanted to know if current would flow in a solution even when one of the poles of the battery was removed and electricity was introduced to the solution through a spark. What he found out was that there was current in an electrolytic solution even if both or one of the electrical poles were out of the solution. He wrote: “I conceive the effects [of electrolysis] to arise from forces which are internal, relative to the matter under decomposition, and not external, as they might be considered, if directly dependent on the poles. I suppose that the effects are due to a modification, by the electric current, of the chemical affinity of the particles through or by which the current is passing” (Davis 435). Faraday's experiments showed that the solution itself was part of the current in electrolysis and it led him to the ideas of oxidation and reduction. His experiments also made him have the idea for the basic laws of electrolysis.
Modern Day Use
Electrolysis has many uses in modern day society. One of them is purifying aluminum. Aluminum is usually produced from the mineral bauxite. The first step they do is to treat the bauxite so it becomes more pure and ends up as aluminum oxide, . Then they melt the aluminum oxide and puts it in an oven. When the aluminum oxide is melted the compound dissociates into its corresponding ions, and . This is where the electrolysis comes in. The walls of the oven function as a cathode and blocks of carbon hanging from above works as an anode. When there is current through the melted aluminum oxide the aluminum ions will move towards the cathode where they will gain electrons and become aluminum metal. The negative oxygen ions will move towards the anode and will there give away some of their electrons and form oxygen and other compounds. The electrolysis of aluminum oxide demands a lot of energy and with modern technology the energy consumption is 12-14 kWh per kg of aluminum (Kofstad).
Electroplating is another use of electrolysis. In electroplating electrolysis is used to put a thin layer of a certain metal over another metal. This is especially useful if you want to prevent corrosion in certain metals, for example iron. Electroplating is done by using the metal you want to have coated in a specific metal act as the cathode in the electrolysis of a solution. The cation of this solution would then be the metal that is wanted as a coating for the cathode. When current then is applied to the solution, the positive cations will move towards the negative cathode where they will gain electrons and form a thin coating around the cathode. To prevent corrosion in certain metals, zinc is often used as the coating metal. Electroplating can also be used to improve the appearance of metals. Using a silver solution will coat a metal with a thin layer of silver so the metal appears to be silver (Christensen).
In the future, electrolysis will have many new uses. Our use of fossil fuels will eventually end and the economy will move from being based on fossil fuels to being based on hydrogen (Kroposki 4). Hydrogen in itself will not act as an energy source but rather an energy carrier. The use of hydrogen will have many advantages over fossil fuels. First of all the use of hydrogen will emit less greenhouse gases when it is used compared to fossil fuels. It can also be produced from clean energy sources which makes the emission of greenhouse gases even less (Kroposki 4). The use of hydrogen fuel cells will improve the efficiency of hydrogen as a fuel source, mainly in transportation. A hydrogen fuel cell has an efficiency of 60 % (Nice 4). That is 3 times as much as the efficiency of a fossil fuel powered car with about 20 % efficiency, which loses a lot of energy as heat to the surrounding environment. The hydrogen fuel cell has less movable parts and does not lose as much energy during its reaction. Another advantage of hydrogen as a future energy carrier is that it is easy to store and distribute and it can be done in many ways (Kroposki 4). This is where it has its advantage over electricity as the energy carrier of the future. Electricity requires a large network of wires to be distributed, and storage of electricity is very inefficient and impractical. Hydrogen can be transported and distributed in a cheap and easy way. It can also be stored without any drawbacks.“Currently, the main methods of producing hydrogen are by reforming natural gas and dissociating hydrocarbons. A smaller amount is produced by electrolysis” (Kroposki 5). Natural gas and hydrocarbons however, will not last forever and this is where industries will have to use electrolysis to acquire hydrogen.
They do this by sending current through water, which leads to hydrogen forming at the cathode and oxygen forming at the anode. The beauty of this is that electrolysis can be performed wherever there is an energy source. That means that scientists and industries can use renewable energy sources like solar power and wind power to produce hydrogen. They will not be reliable on a certain geographic location and can produce hydrogen locally where they need it. This is also beneficial energy wise since less energy is used for transportation of the gas.
Electrolysis plays an important role in modern life. Whether it is production of aluminum, electroplating metals, or producing certain chemical compounds, the process of electrolysis is essential in the daily life of most people. It has been developed thoroughly since its discovery in 1800 and will probably become even more important in the future. The world needs a substitute for fossil fuels and hydrogen seems to be the best candidate. In the future this hydrogen will need to be produced by electrolysis. The process will be improved and will become even more important in daily life than it is now.
Andersen, and Fjellvåg. “Elektrolyse.” Store Norske Leksikon. 18 May 2010.
Christensen, Nils. “Elektroplettering.” Store Norske Leksikon. May 26.
Davis, Raymond E. Modern Chemistry. Austin, Texas: Holt, Rinehart, and Winston, 2005.
Kofstad, Per K. “Aluminium.” Store Norske Leksikon. May 26.http://snl.no/aluminium
Kroposki, Levene, et al. “Electrolysis: Information and Opportunities for Electric Power Utilities.”
National Renewable Energy Laboratory. May 26:1- 33.www.nrel.gov/hydrogen/pdfs/40605.pdf
Nice, and Strickland. “How Fuel Cells Work.” How Stuff Works.
Sani Abacha on July 25, 2019:
aashi on February 16, 2014:
Truly a helpful page
Jason from Indianapolis, IN. USA on April 12, 2012:
Not sure if hydrogen is going to be used to the extent you mention. None the less, great lens.
SALVAONEGIANNAOLCOM from south and west of canada,north of ohio on August 19, 2010: