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Scientists solve titanic puzzle of popular photocatalyst

Posted July 9, 2013

A breakthrough in our understanding of the properties of titania (titanium dioxide) – the basis of self-cleaning window technology – has been made by scientists at UCL, uncovering a decades old misunderstanding that has clouded our knowledge of how mixed phase [1] titania catalysts operate.

By carrying out cutting-edge computational simulations alongside precise experimental measurements of physical samples of the mineral, scientists at UCL found that the widely accepted explanation for how mixed phase titania catalysts operate was misguided. Their discovery, published today in Nature Materials, will help scientists and engineers develop improved photocatalysts, which have applications in clean energy technologies, self-cleaning coatings and a number of other fields.

Since the 1970s, scientists have known that titania is a photocatalyst, a substance which can break down water and other substances on its surface when it is exposed to light. This occurs when photons in the light excite electrons within the atomic structure. These electrons then react with the water molecules, splitting them apart releasing hydrogen, which can be used as a green fuel. The same phenomenon also degrades organic molecules such as oils and grease.

These properties, combined with the fact that titania is cheap and abundant, have made it a widely studied and widely used substance, and the basis of self-cleaning window technology.

“There were about 12,000 scientific articles written about titania last year,” says lead author David Scanlon (UCL Chemistry), “so this is one of the most heavily studied catalysts out there. Despite the mountains of research into this material, the explanation for the observed performance increase when mixed-phase samples were employed instead of single phase materials had remained a mystery for decades.”

While titania’s chemical formula is always the same – one titanium and two oxygen atoms – its molecules can be arranged in different ways, producing different crystal structures and properties.

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