An interesting review article on electrochemical ozone generation will appear in the journal of Ozone Science and Engineering:
The Electrochemical Generation of Ozone: A Review, Paul Andrew Christensen a , Taner Yonar b & Khalid Zakaria c
a School of Chemical Engineering and Advanced Materials, Bedson Building, Newcastle
University, Newcastle upon Tyne, NE1 7RU, United Kingdom
b Engineering and Architecture Faculty, Uluda? Universitesi, 16059, Bursa, Turkey
c School of Civil Engineering and Geosciences, Bedson Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom
Accepted author version posted online: 15 Feb 2013.Published online: 23 Apr 2013.
A brief summary of the article is shown below. A discussion of all methods of ozone generation can be found at the Sparta website.
Most commonly, ozone is produced in the gas phase using the corna discharge method, but it can also be generated in solution at an anode elecrochemically. The electrochemical generation of ozone has advantages including: low voltage operation, the possibility of generating high concentrations of ozone in the gas and liquid phases with high current efficiency, no need for
gas feeds and simple system design.
Essentially, if you directly produce the ozone in water you eliminate the need for feed gas preparation and dissolution steps for ozone water treatment applications. While the process has been shown to work well, it has not scaled up as economically as corona discharge systems and thus large scale ozone generation is done in the gas phase. Nonetheless, commercial electrochemical systems are used in smaller scale systems such as ultrapure water and other applicatios.
Electrochemical ozone generators have employed a variety of materials and designs. Anodes materials typically used are Pt, PbO2 and Boron doped Diamond. Both separated and no separated cells have been employed including so call solid polymer elecrolyte cells using Nafion membrane technology.
While a generally accepted mechanism for electrochemical ozone generation has been proposed, different anode materials result in drastically different results with small quantities of impurities greatly affecting performance.
The early studies of electrochemical ozone generation were carried out at low temperatures in corrosive and, in some
cases, expensive electrolytes and primarily using Pt anodes. Later, the favored anode material was PbO2 in more conventional, acidic electrolytes, at temperatures around 0 ?C. These materials require high current densities for high
current efficiencies, typically ca. 1 A cm?2. It is clear that high ozone current efficiencies can obtained at certain anodes like diamond, but at high energy cost. Ni/Sb-SnO2 anodes show high activity at low current densities which means low production per unit area. some of these new catalysts might be directly deposited on nafion lowering overall cell costs.
While the polymer electrolyte systems offer attractive potential they may preclude use of real world water since Nafion is very sensitive to hardness that can significantly shorten the membrane life time. Another issue with electrochemical ozone systems is either the cost, lifetime or toxicity of the materials used. Despite these issues niche applications are already being developed and the long term potential of electrochemical ozone generation appears bright.