The Preparation And Photocatalytic Performance Study Of Zr-Al Co-doped SrTiO₃

The technology of photocatalysis is an effective avenue in solving the serious energy and environmental problems.Sr Ti O₃ attracts great attention due to its excellent chemical stability,earth-abundance,and non-toxicity.However,the formation of lattice defects in the synthesis process led to the rapid recombination of photogenerated carriers,which seriously reduces its photocatalytic activity.Doping is considered to be one of the most effective methods to promote photocatalytic performance.Al³⁺doping has been demonstrated to be attractive as it could ideally substitute Ti³⁺that serves as the recombination center of photogenerated electrons and holes.However,Ti⁴⁺could also be substituted by Al³⁺in real cases,which leads to great limitations of the Al³⁺doping strategy.Hence,clarifying the substitution mechanism and suppressing the substitution of Ti⁴⁺by Al³⁺is of great significance for promoting the photocatalytic activity of Sr Ti O₃.In this work,efficient Zr–Al co-doped Sr Ti O₃ was prepared via a molten salt-assisted method.X-ray diffraction,transmission electron microscopy,scanning electron microscope,Raman spectroscopy and photoelectron spectroscopy study demonstrated that Zr ions and Al ions homogeneously doped into the Sr Ti O₃crystal lattice in the form of Zr⁴⁺and Al³⁺,respectively.Through the photocatalytic overall water splitting test,the optimal doping amount of Al³⁺and Zr⁴⁺is 0.054（molar ratio of Al/Sr Ti O₃）and 0.03（molar ratio of Zr/Sr Ti O₃）,respectively.H₂ and O₂ evolution rates of 73μmol/h and 34μmol/h respectively were achieved over Zr_0.03Al_0.054:Sr Ti O₃,which is 2.3 times that of Al_0.054:Sr Ti O₃.Complete degradation of 10 ppm methylene blue was achieved over Zr_0.03Al_0.054:Sr Ti O₃ in 50 minutes under the irradiation of 300 W Xenon lamp.Electron spin resonance spectroscopy,photoelectron spectroscopy,inductively coupled plasma optical emission spectrometer and Rietveld refinement studies not only clarify the different kinds of substitution of Al³⁺in Al:Sr Ti O₃,but also demonstrate that the co-doping of Zr⁴⁺effectively suppresses the substitution of Ti⁴⁺by Al³⁺and the formation of[Al³⁺–V_o–Ti³⁺],which enables a further decrease of Ti³⁺concentration.This might be because Zr⁴⁺is easier to substitute Ti⁴⁺than Al³⁺due to the low radius mismatch and the same valence states of Zr⁴⁺and Ti⁴⁺.Fluorescence spectroscopy,electrochemical impedance and photocurrent measurements reveal that the carrier separation of Sr Ti O₃ was significantly promoted after co-doping,which ultimately promote photocatalytic performance.