Chlorine is widely used to disinfect surfaces and municipal drinking water, but it is hazardous to transport and store and can form carcinogenic byproducts, limiting where and how it can be applied. The researchers focused on ozone because it can be produced at the point of use by water electrolysis and then decomposes to oxygen, avoiding persistent residues.
In water electrolysis, an applied electric current splits water into hydrogen and oxygen, and with the right catalyst, shifts the reaction toward ozone instead of oxygen. Nickel- and antimony-doped tin oxide, known as NATO, has been one of the safer and more economical catalyst options for generating ozone directly in water, yet it has degraded too quickly for large-scale deployment, and the new work explains how the same defect sites that promote ozone formation also create pathways for degradation that limit catalyst lifetime.
"Catalysts can make exciting chemistry possible, but catalysts themselves break down over time," said John Keith, R.K. Mellon Faculty Fellow in Energy at Pitt's Swanson School of Engineering. "Under extreme electrolysis conditions, exciting chemistry can start happening, but catalysts can also start breaking down quicker, too. In the oxide-based catalysts we have studied, what forms ozone is paradoxically also suppressing its formation. Now that we understand that, it becomes a fun puzzle to solve how to design ozone-generating sites that do not also cause corrosion reactions that ruin the catalyst."
Computational modeling by Lingyan Zhao, then a Pitt chemical engineering PhD student working with resources at Brookhaven National Laboratory's Center for Functional Nanomaterials, identified how defect sites on the NATO surface influence performance and stability. Quantum chemistry calculations showed that these defects enhance electron transfer and ozone formation, while also binding water in ways that build proton-rich networks of hydroxides and water known to drive corrosion.
Lead author Rayan Alaufey, an international PhD student at Drexel University, carried out extensive electrochemical and materials experiments to test and validate these hypotheses. The combined results confirm that controlling the density and environment of surface defects is central to balancing high ozone activity with resistance to corrosion in tin oxide-based catalysts.
"This work is a testament to how fundamental science and engineering come together to answer long-standing questions and concoct new routes to improved water sanitation technologies," Keith said. The findings point to design rules for next-generation catalysts that could enable practical systems to generate ozone wherever disinfection is needed, reducing dependence on transported chlorine and improving water treatment safety.
Research Report:Electrochemical Corrosion and Catalysis Dynamics of Tin Oxide during Water Oxidation
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