Edge sites on TiO2 are photocatalytic active site

Abstract

Although TiO₂ has been widely used as an efficient photocatalyst, the photocatalytic active sites remain ambiguous. Using rutile TiO₂(110) surfaces with well-defined defects, we herein unambiguously identify that edge sites on TiO₂ surfaces with interstitial Ti³⁺ defects are photocatalytically active. On the oxidized TiO₂(110) surface with TiO₂ islands, chemisorbed CO₂ and CO are photo-inactive; on the TiO₂(110) surface with surface bridging oxygen vacancies and bulk interstitial Ti³⁺ defects, CO₂ and CO chemisorbed at the vacancy sites become photoactive; on the TiO₂(110) surface with TiO₂ islands and interstitial Ti³⁺ defects, CO₂ and CO chemisorbed at the edge sites of TiO₂ islands are also photoactive. CO chemisorbed at the surface oxygen vacancies shows the highest photo-induced desorption probability, while CO₂ chemisorbed at the edge sites of TiO₂ islands with interstitial Ti³⁺ exhibits the highest photo-induced desorption probability. Considering their abundance on powder TiO₂ photocatalysts, the edge sites are among the photocatalytic active sites contributing to TiO₂ photocatalysis.