Anodic Materials for Electrocatalytic Ozone Generation

Ozone has wide applications in various fields. Electrocatalytic ozone generation technology as an alternative method to produce ozone is attractive. Anodic materials have significant effect on the ozone generation efficiency. The research progress on anodic materials for electrocatalytic ozone generation including the cell configuration and mechanism is addressed in this review. The lead dioxide and nickel-antimony-doped tin dioxide anode materials are introduced in detail, including their structure, property, and preparation. Advantages and disadvantages of different anode materials are also discussed. 1. Introduction Ozone is one of the most powerful oxidants currently available [1, 2] and it has an oxidation potential of 2.07？V. Due to its potent oxidative property, ozone has been recognized as a useful chemical in disinfection and sterilization processes. It kills microorganisms, decomposes organic molecules, and removes cyanide, phenols, manganese, detergents, and coloration from aqueous systems. It is used to disinfect portable water, food, and surgical equipment and to treat sewage water, swimming pool, and so forth. It may also be employed as a raw material in the manufacture of certain organic compounds such as oleic acid and peroxyacetic acid [3]. The use of ozone for the purification of water is particularly advantageous as it does not leave any harmful residuals in water [3]. But ozone is unstable and its half lifetime is only about 30？min in water. Thus, it is commonly used by on-site production technology. Traditional ozone production method is corona discharge to air or pure oxygen with the following reaction occurred [3]: In this method, due to the high-frequency AC electric field applied, certain amount of harmful nitrogen oxides will be produced if air is used as the gas source. What is more, the ozone concentration cannot be higher than 3% (by weight). Even by using pure oxygen as the gas source, the ozone gas concentration cannot reach as high as 10% (by weight). The low ozone concentration may have various disadvantages. In particular, because of its low concentration, the dissolved ozone is insufficient to treat the water and results in low operational efficiency. Additionally, dry ozone from the discharge method takes a longer time to dissolve in water than wet ozone from the electrolytic process. To avoid these disadvantages of discharge method, more and more attention shifted to the electrocatalytic method. The electrocatalytic ozone generation method is to oxidize water to ozone on the anode. It is well known that water is more