Preparation And Photocatalytic Properties Of Ag And Cu Co-Doped TiO₂ Nanotubes

Titanium dioxide is widely used in photocatalysis because it is non-toxic,inexpensive,and chemically stable.Among many microstructures,TiO₂nanotubes are of great interest because of their high specific surface area and high electron transfer properties.In this experiment,TiO₂nanotubes were produced by anodic oxidation method,and Cu₂O/TiO₂nanotubes,Ag/TiO₂nanotubes and Ag/Cu₂O/TiO₂nanotubes were prepared by electrochemical deposition method on this substrate,and their physicochemical and photocatalytic properties were investigated,and the specific results are summarized as follows.Firstly,TiO₂nanotubes with open top and regular structure were fabricated by anodic oxidation at a voltage of 50 V and a time of 2 h.A series of Cu₂O/TiO₂nanotubes were prepared by regulating the concentration of precursors and the deposition voltage to control the deposition amount of Cu₂O under the conditions of constant deposition time and deposition voltage with TiO₂nanotubes as the substrate.The results showed that with the increase of the deposition voltage,Cu₂O showed a dendritic shape and accumulated at the top of the TiO₂nanotube mouth,and XRD and XPS analyses indicated the formation of Cu₂O.When the precursor concentration was20 m M and the deposition voltage was 3 V,the current density generated by Cu₂O/TiO₂nanotubes reached 0.975 m A/cm²under illumination,corresponding to a photoelectric conversion rate of 22.08%,and the theoretical hydrogen production reached 18.19μmol·cm^-2·h^-1.When the electrodeposition voltage was 5 V,the Cu₂O/TiO₂nanotubes has the best photocatalytic degradation effect on Rhodamine B（Rh B）,and the degradation rate reached 80.5%.Secondly,a series of Ag/TiO₂nanotube composites were prepared by electrochemical deposition of Ag nanoparticles loaded on TiO₂nanotubes with regulated deposition voltages,and the characterization results showed that the Ag nanoparticles produced by electrochemical deposition were agglomerated on the surface of TiO₂nanotubes and partially entered into the interior of TiO₂nanotubes,mainly composed of two forms,Ag singlet and oxide.Compared with pure TiO₂nanotubes,the photogenerated current density of Ag/TiO₂nanotubes was significantly enhanced and the photocurrent was more stable,reaching 0.675 m A/cm²when the deposition voltage was 1 V,corresponding to a photoelectric conversion of 15.28%and a theoretical hydrogen production of 12.59μmol·cm^-2·h^-1.Ag/TiO₂nanotubes showed the highest degradation effect against Rh B when the electrodeposition voltage was 3 V,and the degradation rate reached 76.7%.Finally,Cu and Ag were co-doped inside the TiO₂nanotubes by electrochemical deposition,and a series of Ag/Cu₂O/TiO₂nanotubes were prepared by regulating the deposition voltage.The results show that:the main form of Cu element is Cu₂O,and Ag element has two forms of Ag monomer and Ag oxide;when the deposition voltage is 2 V,the photogenerated current density of Ag/Cu₂O/TiO₂nanotubes reaches 1m A/cm²,corresponding to a photoelectric conversion of 22.65%,and the theoretical hydrogen yield is 18.66μmol·cm^-2·h^-1.Meanwhile,the degradation rate of the composite nanotubes against Rh B reached 79%;the results of PL and EIS tests showed that the Ag/Cu₂O/TiO₂nanotube catalysts could effectively inhibit the composite of photogenerated carriers;the light absorption range of Ag/Cu₂O/TiO₂nanotubes extended to the visible region（about 520 nm）,and the forbidden band width was about 2.38 e V.