Hydrogen can be produced via electrolysis using OTEC electricity. Hydrogen fuel can be produced from methane or by electrolysis of water. This is possible by using renewable energy to generate hydrogen by electrolysis of water. Membrane cell electrolysis employs permeable membrane as an ion exchanger. A by-product of hydrogen production via water electrolysis was heavy water. This method is less expensive than the previous Castner process (the electrolysis of sodium hydroxide). Coupling the RWGS with the water electrolysis process will yield methane and oxygen. Isolated hairs can be removed with tweezers or electrolysis. Fluorine is produced by the electrolysis of molten potassium bifluoride. The carbon electrodes are similar to those used in the electrolysis of aluminium. This is why ozone is not produced during typical water electrolysis. Faraday's belief had been that ions were produced in the process of electrolysis. PEMFCs generate electricity and operate on the opposite principle to PEM electrolysis, which consumes electricity. Conventional alkaline electrolysis has an efficiency of about 70%. Today's process is a combination of chlorination and electrolysis.