Oxygen Reduction Activity of TiO2 Single Crystals in Acidic Media

Development of nonplatinum electrocatalysts for the oxygen reduction reaction (ORR) is necessary for wide commercialization of polymer electrolyte fuel cells. We focused on Group 4 and 5 metal oxide-based compounds for use as nonprecious metal cathodes. We need to investigate the active sites of oxide-based cathodes at the atomic level to enhance the oxygen reduction activity. We used rutile TiO2 single crystals with (100), (001), (110), and (110) faces as model electrodes. The ORR activity strongly depended on the crystal face. In addition, reduction under pure hydrogen at 600 degrees C for 1 h was effective in enhancing the ORR activity of the (110) plane.