Abstract: Ozone is a powerful and versatile oxidant that is good for many applications including sterilization of drinking water, rejuvenation of waste waters, and chemical syntheses. Most of the man-made ozone for the said uses comes from corona discharge of oxygen gas. From the aspects of simplicity, efficiency, voltage level and space area, generation of ozone by water electrolysis has all advantages over the discharge means. It requires an catalyst deposited on the anode of electrolyzer for generating ozone gas directly in water, and the anode material should be affordable, long-lived and reliable. For the said device to become commercially viable, the scale buildup, particularly calcium carbonate, on the cathodes must also be resolved. Tests have shown that the provision of a low vacuum over the electrodes of electrolyzer can assist the device to deliver a consistent ozone throughput for a long period of time.