Synthesis And Photocatalytic Properties Of TiO₂ Composite Nanomaterials

As a semiconductor material,TiO₂ has attracted considerably attention.However,due to its wide band gap and weak visible light absorbance,it can be excited only by the ultraviolet radiation,which confines its applications in various fields.In this study,a ternary nanocomposite Bi₂S₃/graphene quantum dots/TiO₂ nanowire arrays?Bi₂S₃/GQDs/TNWs?hybrids are constructed through electrodeposition and electrophoretic deposition.We report the synthesis of novel TiO₂ nanostructures simultaneously doped with nitrogen and sensitized with Mn-doped CdS quantum dots.The composites were characterized to analysize their morphology,microstructure and photocatalytic performance,including Raman spectroscopy,X-ray diffraction?XRD?,transmission electron microscopy?TEM?,emission field scanning electron microscope?FE-SEM?,ultraviolet-visible diffuse reflectance spectroscopy?UV-vis?,photoluminescence spectra?PL?,photoelectrochemical measurements and ect.And the possible mechanism is explored.The main contents are as follows:?1?TiO₂ nanostructures were synthesized via an alkaline hydrothermal growth process,incuding nanoleaf arrays,nanowire/nanoleaf arrays,nanowire arrays,nanowire/nanoflower arrays,nanowire/nanoleaf/nanoflower arrays.The effects of reaction temperature,reaction time and concentration of NaOH solution on the morphology of TiO₂ nanomaterials have been investigated.The photocurrent response of TiO₂ nanomaterials with different structures was investigated.?2?TiO₂ nanowire/nanoleaf arrays were modified simultaneously with nitrogen-dop and Mn-doped CdS quantum dots.The photocatalytic activity of as-prepared samples was evaluated by degradation of terephthalic acid.Meanwhile,the photocatalytic reaction mechanism of the composites was analyzed.These co-doped novel nanocomposite structures displayed a significantly enhanced photoresponse compared with a single doping or sensitization strategy.Thisenhancement was attributed to the double synergistic effect of N doping of TiO₂,which facilitated hole transfer/transport from the sensitizers to TiO₂ via oxygen vacancy states mediated by the N and Mn doping that created electronic states in the CdS mid-gap region,thus altering the charge separation and recombination dynamics in addition to tuning the optical properties.?3?Ternary composite photoelectrode of Bi₂S₃/GQDs/TNWs was fabricated by using a combined technique of controllable electrodeposition and electrophoretic deposition.For evaluating the activity of the as-prepared ternary composite,the photoelectrochemical activity was examined by reducing Cr?VI?.The experiment results show that the photoelectrochemical activity to reduce aqueous Cr?VI?of Bi₂S₃/GQDs/TNWs after 80 min increases by 76% than the pristine TNWs.According to the electron quenching behavior,the GQDs middle layer not only acts as benign photosensitizer for enhancing spectral absorption,but also as electron transporter which accelerates efficient separation of photon-generated carriers.