Ozone is seen an a safer and more environmentally friendly alternative to chlorine for water disinfection, but the efficient generation of ozone on-demand and at commercially relevant scales has been hindered by catalytic degradation problems.
A team of researchers from Drexel University (Philadelphia, Pa.; www.drexel.edu), University of Pittsburgh (Pitt; www.pitt.edu) and Brookhaven National Laboratory (BNL; Upton, N.Y.; www.bnl.gov) has used quantum chemistry modeling to elucidate the atomic-scale features of electrodes used in the generation of ozone from water electrolysis.
Focusing on doped tin-oxide electrodes used in ozone generation via electrolysis, the work pinpointed certain surface defects that could directly promote ozone formation, while also identifying similar surface sites that can lead to corrosion and failure. “What makes this work unique from an industrial standpoint is that it provides clear design rules rather than just performance data, allowing manufacturers to focus on maximizing the most favorable active sites while minimizing those that lead to degradation. This addresses a long-standing challenge in balancing activity and durability and opens a path toward scalable, chlorine-free disinfection technologies,” explains Maureen Tang, Drexel University professor of chemical and biological engineering.
To gain such atomic-scale insights, quantum chemistry models expanded the analyses, going far beyond what is possible with experimentation alone. “Ozone formation depends on subtle atomic- and electronic-scale effects that are hard to disentangle experimentally when many processes occur at once. Quantum chemistry allows us to model how oxygen and water interact on clean and defective surfaces and to determine whether a reaction would lead to ozone, oxygen or degrade the catalyst. Experiments show what is happening overall, but quantum chemistry is an important key to help understand why,” says John Keith, professor at Pitt’s department of chemical and petroleum engineering.
The quantum model developed by Pitt researchers showed that the same sites required for ozone formation can also promote unwanted side reactions that degrade the catalyst, directly linking atomic-scale structure to macroscopic performance. “Quantum chemistry was used to model how electrons rearrange at the catalyst surface during water oxidation. By simulating different dopants and surface defects at the atomic level, we identified atomic-scale reaction pathways that are difficult to isolate experimentally,” adds Keith.
This work is especially notable in that it is among the first to integrate experimental and computational-chemistry investigation of ozone production from water electrolysis. “The next phase focuses on expanding the scope to understand if the tradeoff between catalyst activity and stability is universal. Are there any ways to break this scaling relation so that we have materials that are both active and stable? We will explore new dopants, microstructures and compositions to answer this question,” says Tang.