When water comes in for a landing on the common catalyst titanium oxide, it splits into hydroxyls just under half the time. Water's oxygen and hydrogen atoms shift back and forth between existing as water or hydroxyls, and water has the slightest advantage, like the score in a highly competitive tennis game.
When a molecule of water comes in for a landing on the common catalyst titanium oxide, it sometimes breaks up and forms a pair of molecule fragments known as hydroxyls. But scientists had not been able to show how often the breakup happened. Now, researchers have determined that water is only slightly more likely to stay in one piece as it binds to the catalyst surface than it is to form the hydroxyl pairs.
The result – water's advantage is so small – might surprise some chemists. But understanding that small advantage has wide-ranging significance for a variety of potential applications in industries that use titanium dioxide. These industries include alternative fuel production, solar energy and food safety, and even self-cleaning windows. It will also help scientists better understand how acids behave and expand their knowledge of how molecules split.
"How water binds was the big question," said chemist Zdenek Dohnalek at the Department of Energy's Pacific Northwest National Laboratory. "Chemists had mixed information from a lot of different methods, and theorists also had ideas. Using a unique combination of instruments, we've finally solved it." The team reported the work in the Proceedings of the National Academy of Sciences