Electrolysis
Electrolysis uses electricity to break down an ionic compound that is molten or dissolved (the electrolyte). Positive ions (cations) move to the negative cathode and gain electrons (reduction). Negative ions (anions) move to the positive anode and lose electrons (oxidation). In aqueous solutions, water's and compete: hydrogen forms at the cathode unless the metal is less reactive than hydrogen; oxygen forms at the anode unless a halide is concentrated.
≈ 45 minElectroplating and fuel cells
In electroplating, the object to be coated is the cathode, the plating metal is the anode, and the electrolyte contains ions of the plating metal. Copper is purified the same way: an impure copper anode dissolves and pure copper deposits on the cathode. A hydrogen–oxygen fuel cell combines hydrogen and oxygen to produce electricity directly, with water as the only product.
≈ 30 min