Doping rh into tio2as a visible-light-responsive photocatalyst: The difference between rutile and anatase

Abstract

Incorporation of alien atoms into TiO2 is an effective means to extend its light absorption edge for utilizing solar energy sufficiently. Herein, taking rutile and anatase as precursors, respectively, Rh element was attempted to dope into TiO2 by an immersion-calcination process. The results showed that Rh species were readily immerged in the crystal structure of rutile at a temperature above 973 K, while they were constantly positioned on the surface of anatase in a separate form of Rh2O3 nanoparticle even at 1173 K. Density functional theory simulations revealed that the Rh-rutile sample owned a higher negative formation energy than Rh-anatase. Under visible light irradiation and in the presence of ascorbic acid as a sacrificial reagent, photocatalytic hydrogen evolution activity over Rh-doped rutile was about 50 times of that over Rh-doped anatase powders. The present work demonstrates the roles of the crystal phase in atom doping that eventually dominates photocatalytic activities.