Electrolysis

Electrolysis applies a direct electric current to force a chemical or physical reaction that would not happen on its own. In industry, it is a key step for extracting elements from natural sources like ores, using a device called an electrolytic cell. The minimum voltage required to start the process is known as the decomposition potential. The term itself comes from Greek: “lysis” means to separate or break, so electrolysis literally means “breakdown via electricity.”

Michael Faraday introduced the word “electrolysis” in 1834, combining the Greek for “amber” (associated with electricity since the 1600s) with “dissolution.” However, the technique was used to study reactions and isolate pure elements before Faraday named or formally described it.

Early experiments date to 1785, when Martin van Marum used an electrostatic generator to reduce tin, zinc, and antimony from their salts—though he did not realize he was performing electrolysis. In 1800, William Nicholson and Anthony Carlisle connected two wires to a voltaic pile and placed the other ends in water; they saw bubbles form, with hydrogen at one wire and oxygen at the other. Luigi Galvani’s 1791 frog-leg experiments suggested electricity from animal muscle, prompting Alessandro Volta’s own tests, which later informed Humphry Davy’s ideas. Davy hypothesized that combining elements into a compound releases electrical energy, and he created decomposition tables showing the energy needed to break compounds apart.

In 1817, Johan August Arfwedson identified lithium in samples but could not isolate it. William Thomas Brande achieved this in 1821 using electrolysis, and two years later refined the process with lithium chloride and potassium chloride to produce lithium and lithium hydroxide. During Davy’s later work, Michael Faraday became his assistant and, while studying electrolysis, discovered two fundamental laws governing it. Around the time of James Clerk Maxwell and Faraday, scientists focused on electropositive and electronegative behaviors.

Paul Émile Lecoq de Boisbaudran discovered gallium in November 1875 by electrolyzing gallium hydroxide, producing 3.4 mg of the element, and presented it to the Académie des sciences the next month. On June 26, 1886, Henri Moissan electrolyzed anhydrous hydrogen fluoride to obtain gaseous fluorine; two days later he demonstrated this before the Académie. Earlier attempts using fluoride salts had killed several chemists, including Paulin Louyet and Jérôme Nicklès. In 1886, Charles Martin Hall (America) and Paul Héroult (France) both filed for U.S. patents on aluminum electrolysis; Héroult filed in May, Hall in July. Hall proved his method predated Héroult’s through letters to his brother, securing the patent. Their Hall–Héroult process slashed aluminum’s price from four dollars to thirty cents per pound. In 1902, Polish engineer Stanisław Łaszczyński patented a method for electrolyzing copper and zinc.

Key milestones include: 1785—van Marum’s electrostatic generator reduces tin, zinc, and antimony from salts. 1789—Adriaan Paets van Troostwijk and Jan Rudolph Deiman electrolyze water with an electrostatic generator, producing small amounts of hydrogen and oxygen. 1800—Nicholson and Carlisle (and Johann Ritter) achieve the first sustained water electrolysis using a voltaic pile. 1808—Humphry Davy discovers potassium, sodium, barium, calcium, and magnesium via electrolysis. 1821—William Thomas Brande isolates lithium by electrolyzing lithium oxide. 1834—Faraday publishes his two laws of electrolysis, provides a mathematical explanation, and coins terms like electrode, electrolyte, anode, cathode, anion, and cation. 1875—Lecoq de Boisbaudran discovers gallium via electrolysis. 1886—Moissan discovers fluorine; Hall and Héroult develop the aluminum process. 1890—Castner–Kellner process for sodium hydroxide. 1902—Łaszczyński obtains copper via electrolysis. 1930—Modern chlor-alkali process (electrolysis of brine for chlorine and sodium hydroxide) becomes an important industrial method.