Amino Acids Assisted Preparation Of Nanoscale TiO₂ And Derived Composite Photocatalysts

TiO₂ nano photocatalysts were prepared by hydrolysis and hydrothermal synthesis with amino acids as biological template.The prepared TiO₂ nanomaterials were fully characterized.Amino acids could regulate the nucleation growth of TiO₂and induce the formation of the spherical structure.In the process for the preparation of TiO₂ by amino acids assisted hydrolysis,the effects of calcination temperature,the amount of amino acids,the kind of amino acids and the amount of butyl titanate on the photocatalytic activities of TiO₂ were investigated.Under the optimal reaction conditions,the photocatalytic degradation rate of methyl orange reached 99.3%.In the process for the preparation of TiO₂ by amino acids assisted hydrothermal synthesis,the effects of calcination temperature,the amount of amino acids,hydrothermal reaction temperature and time on the photocatalytic activities of TiO₂ were investigated.Under the optimal reaction conditions,the photocatalytic degradation rate of methyl orange reached 98.5%.The prepared TiO₂ exhibited excellent photocatalytic activity,which was mainly ascribed to the large BET surface area and regular structure.Furthermore,the possible growth mechanism of spherical structure TiO₂ nano photocatalysts assisted by amino acids was discussed.BiOI/TiO₂ composite photocatalysts were synthesized by biomimetic synthesis and hydrothermal synthesis with amino acids as biological template.The as-prepared photocatalysts were fully characterized and the formation of p-n heterojunction was confirmed.BiOI/TiO₂compositephotocatalystsexhibitedmoreexcellent photocatalytic performance than the pure TiO₂ and BiOI in the photocatalytic selective hydroxylation of phenol.Phenol aqueous solution was irradiated under visible light for 30 min.The conversion of phenol was 13.5%,and the selectivity of dihydroxybenzene was 92.1%.The enhancement of photocatalytic performance was mainly ascribed to the exposed reactive facets,narrow band gap and effective separation of the photogenerated electron and hole.The effects of Bi/Ti molar ratios,hydrothermal reaction time and temperature on the photocatalytic activities of BiOI/TiO₂ were investigated.Under the optimal reaction conditions,the photocatalytic degradation rate of methyl orange reached 99.8%.The reusability tests demonstrated that BiOI/TiO₂ composite photocatalysts had excellent stability.Furthermore,active-species trapping experiments indicated that?OH played a dominant role in the photocatalytic selective hydroxylation of phenol.The charge transfer process of BiOI/TiO₂ composite photocatalysts and a possible mechanism for photocatalytic selective hydroxylation of phenol were proposed.