Bringing Disorder To Titanium Dioxide

By hydrogenating titanium dioxide nanocrystals, researchers have engineered disorder into the material—a change that appears to enhance TiO₂’s properties so that it absorbs beyond the ultraviolet range into the visible and infrared spectrum (Science, DOI: 10.1126/science.1200448). The transformation could expand TiO₂’s use as a photocatalyst for a variety of solar-driven clean energy and environmental technologies. A team led by Samuel S. Mao, of Lawrence Berkeley National Laboratory and the University of California, Berkeley, devised the concept of disorder engineering and used a hydrogenation process so that it produces TiO₂ with a crystalline core and a highly disordered surface layer. The core maintains TiO₂’s catalytic properties while the surface enhances visible and infrared absorption, promoting catalytic activity. The material also undergoes a dramatic color change during hydrogenation, from bright white to black. The researchers show the disordered material is capable of photooxidizing organic molecules in water and can produce hydrogen from water and sunlight at high efficiency.