One-step synthesis of visible active C[sbnd]N[sbnd]S-tridoped TiO2 photocatalyst from biomolecule cystine

Abstract

CNS-tridoped TiO2 nano-particles were synthesized through simple one-step sol–gel reactions in the presence of biomolecule cystine. This biomolecule could not only serve as the source for C, N and S tridoping, but also could control the light absorption in visible region and separation efficiency of photogenerated charge carriers. The resulting materials were characterized by X-ray diffraction (XRD), Nitrogen adsorption–desorption, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and surface photovoltage spectrum (SPS). It was found that S6+ was incorporated into the lattice of TiO2 through substituting titanium atoms; N might coexist in the forms of substituted N (NOTi) and interstitial N (OTiN) in TiO2; and C could form a mixed layer of carbonate on the surface of TiO2. Further, the addition of cystine greatly improved the light absorption in visible region and the separation efficiency of photogenerated charge carriers. The photocatalytic activities of the as-synthesized samples were evaluated for the degradation of phenol under simulated sunlight irradiation. Results showed that CNS-tridoped TiO2 exhibited higher sunlight photocatalytic degradation efficiency than that of undoped and P25 TiO2 samples. The enhanced photocatalytic activity could be attributed to the small crystallite size, intense light absorption in visible region, large amount of surface hydroxyl groups and high separation efficiency of photogenerated charger carriers.