Catalysts — substances that increase the rate of chemical reactions without undergoing chemical change themselves — break the strong O2 bond, allowing single atoms of oxygen to bind with the ethylene to form ethylene oxide. Silver is the main catalyst for making ethylene oxide, but it produces two molecules of CO2 for every molecule of ethylene oxide; adding chlorine brings it to about one molecule of CO2 for every two ethylene oxide molecules produced.
Aware of the safety and environmental implications of current chlorine-based industrial production methods, Sykes and Montemore looked for elements they could add to the silver catalyst to substitute for chlorine. “The answer was nickel,” Sykes said, “which surprised us, because we couldn’t find anything in the scientific or patent literature about nickel despite its being a common and inexpensive element used in many other catalytic processes. Could seventy-plus years of industrial R&D have missed it?”
Fundamental experiments conducted at Tufts were promising. Using a _single-atom_ alloy concept developed by Sykes more than a decade earlier, the researchers were able to discover that by adding individual atoms of nickel to silver, they could test how the material would work as a catalyst. “Our results indicated that it may be applicable to real industrial catalysts,” Sykes said.
To test it, he enlisted Christopher, the UCSB Rinker Founder's Chair and [Mellichamp Chair in Sustainable Manufacturing](https://www.sustech.ucsb.edu/), to make a new formulation of the silver catalyst by adding tiny amounts — individual atoms — of nickel. “Selective oxidation is one of the more challenging reactions, and so I wouldn’t have been surprised if it hadn’t worked,” said Sykes. But it did.
“Anika took on the extremely difficult technical challenge of developing a reproducible protocol for incorporating nickel atoms into the silver catalyst,” Christopher said. “The difficulty of doing that could be why the effect we observed was never previously reported."