Visible-light-active Rh-doped SrTiO3: Effect of Rh doping on the structural characteristics contributing to outstanding photocatalytic activity

Strontium titanate photocatalysts were doped with rhodium (0, 1, 5, 10, and 15 at%) via a hydrothermal method to enhance their visible light absorbance. The samples were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, infrared spectroscopy, nitrogen adsorption, scanning and transmission electron microscopy, diffuse reflectance spectroscopy, and photoluminescence measurements. Their photocatalytic activity was evaluated by the photocatalytic oxidation of phenol under visible light irradiation, using the non-Rh-containing sample as a reference. All the applied rhodium was successfully incorporated into the cubic crystal lattice. Rhodium doping resulted in significantly enhanced visible light absorption and suppressed charge recombination. The photocatalytic activity was enhanced to an exceptionally large degree: the best sample completely degraded phenol in 1 h under visible light. The optimal rhodium amount was found to be 5 at%. The high photocatalytic activity was attributed to the resultant effect of enhanced visible light absorbance, suppressed charge recombination, and high Rh 3+ /Rh 4+ ratio. • Doping SrTiO 3 with Rh results in remarkable visible light excitability. • Enhanced photoactivity is achieved with a low-performance light source. • Rh replacing Ti in the lattice decreases crystallite size due to crystal strains. • Photocatalytic phenol degradation activity under visible light is vastly increased. • The optimum amount of Rh dopant is 5 at%.