How Anode Material Affect the Electrochemical Ozone Production Efficiency?

How Anode Material Affect the Electrochemical Ozone Production Efficiency?

Ozone (O3) is one of the strongest oxidants used for disinfection, sterilization, green oxidation of pollutants, water, and waste treatment, wood pulp bleaching, and chemical synthesis. The extending of application is attributed to oxidizing properties of O3. Ozone provides green oxidation since the decomposition of ozone leads to environmentally friendly products (O2). Electrochemical ozone production (EOP) has been much attended to in the last decade because there are more advantageous than the classical corona discharge (CCD) technology. The electrochemical method can generate high current efficiency and high concentration of dissolved ozone and does not require high voltage.

Electrochemical ozone production is formed by the electrolytic decomposition of water at the anode. The generation of ozone in electrochemical processes severely competes with O2 evolution. Thermodynamically, oxygen evolution is strongly favored versus ozone production.

Thus, the inhibition of O2 evolution is the first requirement for an efficient generation of O3 at a reasonable current. This can be achieved by a suitable choice of the electrode material or the use of additives that partially inhibits the oxygen evolution reaction via blocking of its active sites. Physical and chemical stabilities of electrodes are the second requirement since the generation of O3 needs a very high anodic potential. Thus, materials for electrochemical generation of ozone must have a high overpotential of oxygen evolution and should also be stable to strong anodic polarization in the electrolyte.

Various anodes have been studied for electrochemical ozone production such as platinum, diamond, alpha- and beta-PbO2, Pd, Au, dimensionally stable anode (DSA), glassy carbon, SnO2–Sb2O5, and Ni–Sb–SnO2. Gold, DSA, and glassy carbon electrodes give low current efficiencies of <1%. Platinum shows higher current efficiency from 6.5% to 35% but only at a very low temperature (−50 °C) and at room temperature, the current efficiency fell to 0.5%. PbO2 anodes can produce ozone at a current efficiency of 13% at room temperature, and for Ni–Sb–SnO2 composite, coat on Titanium mesh shows higher current efficiency of ozone production (>36.5%). Electrochemical ozone production also depended on the quantity of active coating materials.