Hopping hydrogen

The behavior of individual hydrogen atoms on titanium oxide surface reveals intriguing details about a popular oxide catalyst

Scanning tunneling images (left, from top) show atoms on the titanium oxide catalyst surface before and after water adsorption and after hydrogen hopping. Light blue oxygen atoms appear as depressions, red titanium atoms as protrusions. Yellow indicates hydrogen atoms from the water molecule. On the right is a model showing water splitting.

Researchers at Pacific Northwest National Laboratory and the University of Texas at Austin discovered that a single hydrogen atom just can’t keep still after it splits from a water molecule on the surface of the catalyst rutile titanium oxide. The hydrogen atom hopscotches across the oxygen atoms that stud the surface of the catalyst, while the hydrogen on what is left from water remains fixed, suggesting that the electronic structure of this popular catalyst is not entirely as it seems.

By understanding how water’s atoms behave on the catalyst surface, scientists and engineers may be able to develop technologies that use abundant, free sunlight to split water to generate hydrogen gas, a possible alternative fuel for everything from heating homes to powering automobiles.

The researchers plan to study the titanium oxide material at higher temperatures to see how fast the hydrogen atoms move. They are also working on developing a detailed understanding of the underlying mechanisms and involved intermediate species.