Why silver speeds photocatalysis

The mystery surrounding why silver deposits on the surface of titanium dioxide (titania) make the material a better photocatalyst for breaking down some organic molecules but not others might have been cleared up. 

Rose Amal and colleagues from the University of New South Wales, Australia, have explained how the silver removes electrons from titania, making the electrons and holes created by UV light less likely to recombine. This increases the number of holes in the material. Because holes catalyse the breakdown of some organic molecules at the surface, this increases the efficiency of catalysis for those molecules.  

Other molecules are broken down by hydroxyl radicals on the surface of the material, and for these molecules the silver has little effect. 

Photocatalysis is a promising technology for removing organic matter from air and water and 
the authors hope their work will have practical implications in this field. 
Madelaine Chapman