Heterostructured ZnFe_2O_4/Fe_2TiO_5/TiO_2 Composite Nanotube Arrays with an Improved Photocatalysis Degradation Efficiency Under Simulated Sunlight Irradiation

To improve the visible light absorption and photocatalytic activity of titanium dioxide nanotube arrays(TONTAs), ZnFe_2O_4(ZFO) nanocrystals were perfused into pristine TONTA pipelines using a novel bias voltageassisted perfusion method. ZFO nanocrystals were well anchored on the inner walls of the pristine TONTAs when the ZFO suspensions(0.025 mg m L^(-1)) were kept under a60 V bias voltage for 1 h. After annealing at 750 °C for2 h, the heterostructured ZFO/Fe_2 TiO_5(FTO)/TiO_2 composite nanotube arrays were successfully obtained. Furthermore, Fe^(3+)was reduced to Fe^(2+)when solid solution reactions occurred at the interface of ZFO and the pristine TONTAs. Introducing ZFO significantly enhanced thevisible light absorption of the ZFO/FTO/TONTAs relative to that of the annealed TONTAs. The coexistence of type I and staggered type II band alignment in the ZFO/FTO/TONTAs facilitated the separation of photogenerated electrons and holes, thereby improving the efficiency of the ZFO/FTO/TONTAs for photocatalytic degradation of methylene blue when irradiated with simulated sunlight.

Decoration of vertically aligned TiO2 nanotube arrays with WO3 particles for hydrogen fuel production

WO3 decorated photoelectrodes of titanium nanotube arrays （W-oxide TNTAs） were synthesized via a two-step process, namely, electrochemical oxidation of titanium foil and electrodeposition of W-oxide for various interval times of 1, 2, 3, 5, and 20 min to improve the photoelectrochemical performance and the amount of hydrogen generated. The synthesized photoelectrodes were characterized by various characterization techniques. The presence of tungsten in the modified TNTAs was confirmed using energy dispersive X-ray spectroscopy （EDX）. Field emission scanning electron microscopy （FESEM） and high resolution transmission electron microscope （HRTEM） proved the deposition of W-oxide as small particles staked up on the surface of the tubes at lower deposition time whereas longer times produced large and aggregate particles to mostly cover the surface of TiO2 nanotubes. Additionally, the incorporation of WO3 resulted in a shift of the absorption edge toward visible light as confirmed by UV-Vis diffuse reflectance spectroscopy and a decrease in the estimated band gap energy values hence, modified TNTAs facilitated a more efficient utilization of solar light for water splitting. From the photoelectrochemical measurement data, the optimal photoelectrode produced after 2 min of deposition time improved the photo conversion efficiency and the hydrogen generation by 30% compared to that of the pure TNTA.

Photoelectrochemical performance of TiO_(2) nanotube arrays by in situ decoration with different initial states

Here,carbon dots(CDs) only or nanocomposites of CDs and TiO_(2)(CDs-TiO_(2)) were used to decorate titanium dioxide nanotube arrays(TiO_(2)NTs) in situ by solvothermal method.Two initial states of TiO_(2)NTs were prepared for contrast,including the amorphous TiO_(2)NTs(TiO_(2)NTs-0) just experienced anodic oxidation process and that further calcined TiO_(2)NTs(TiO_(2)NTs-450).It was found that the newborn CDs or CDs-TiO_(2)were more likely to anchor on TiO_(2)NTs-0 than the calcined TiO_(2)NTs-450,and more Ti-C bonds were found in the composites which were derived from TiO_(2)NTs-0 after the solvothermal treatment.An evident photocurrent could be demonstrated for either CDs or CDs-TiO_(2)decorated TiO_(2)NTs once exposed to visible light.And CDs-TiO_(2)NTs-0 showed the highest photocurrent density(4.51 μA·cm^(-2)).However,the results of photodegradation measurements revealed that CDs-TiO_(2)decorated TiO_(2)NTs with different initial states(especially CDs-TiO_(2)-TiO_(2)NTs-0) showed more excellent photocatalytic activity under both ultraviolet(UV) and visible light illumination.