Fabrication Of Functionalized TiO₂Nanotube Arrays And Their Photocatalytic Application

As an n-type semiconductor material, titanium dioxide （TiO₂） is widelyconcerned in photocatalytic application because of its chemieal stabil ity, highcatalytic efficiency, nontoxicity, and low cost. However, the practical application ofTiO₂is retarded by its wide band gap, high recombination rate of the photogeneratedelectron-hole pairs, poor adsorbability to most of organic contaminants, poorabsorption and poor recovery. Nowdays, many researchers have been developed somemethods to solve the problems, such as ion doping, noble metal deposition andsemiconductor combination.TiO₂nanotube arrays prepared by electrochemical anodic oxidation weremodified with noble metal, semiconductor or composite based on graphene to extendthe absorption of TiO₂to the visible spectrum region, improve the separationeffeciecy of photogenerated carriers, achieve the recycle, enhance the adsorptivity toorganic pollutants, or increase photocatalytic efficiency. The main research contentsare listed below:（1） Fabrication, characterization and photocatalystic application of Ag₂O/TiO₂NTs: Ag/TiO₂NTs were prepared through a pulsed electrodepositon method, and thenthe Ag/TiO₂NTs were potentio-statically anodized in0.5M NaOH electrolyte at0.5Vfor30min at25°C to fabricate Ag₂O nano-network on TiO₂NTs. Compared with bareTiO₂NTs, the resulting photocatalyst showed stronger absorption in visible spectrumregion and exhibited higher photocatalytic degradation efficiency of AO7under thesimulated solar light.（2） Fabrication, characterization and photocatalystic application ofZn_xCd_1-xS/TiO₂NTs: Zn_xCd_1-xS was fabricated on the surface of TiO₂NTs by one-stepcyclic voltammetry electrodeposition technique. It was also studied the effect ofdifferent Zn/Cd ratio on the degradation efficiency of methylene blue （MB）.Compared with the unmodified TiO₂NTs, Zn_xCd_1-xS/TiO₂NTs showed the strongerabsorption in visible spectrum region and exhibited higher photocatalytic degradationefficiency. When the Zn/Cd ratio is1/3, MB degradation efficiency ofZn0.25Cd0.75S/TiO₂NTs is the highest. Moreover, compared with CdS modified TiO₂NTs, Zn_xCd_1-xS/TiO₂NTs are much more stable.（3） Fabrication, characterization and photocatalystic application of Au/RGO/TiO₂NTs: Au nanoparticles and reduced graphene oxide co-decorated TiO₂nanotube arrays （Au/RGO/TiO₂NTs） were prepared through a simple one-stepconstant-potential electrolysis of chloroauric acid and graphene oxide on TiO₂NTs.Compared with Au/TiO₂NTs, RGO/TiO₂NTs and un-modified TiO₂NTs, theAu/RGO/TiO₂NTs exhibited the highest efficiency （nearly100%） in photocatalyticdegradation of methyl orange （MO） under simulated solar light irradiation. The highlyefficient photocatalytic activity is associated with broad absorption in the visible lightregion, increased photoinduced charge separation through transferring photogeneratedelectrons from TiO₂NTs to both Au and RGO, as well as the strong adsorption abilityof RGO to MO molecules. Moreover, the Au/RGO/TiO₂NTs has an excellent stability.