Rui Lei

Hydrothermal synthesis of CdS nanorods anchored on α-Fe2O3 nanotube arrays with enhanced visible-light-driven photocatalytic properties

As an n-type semiconductor with an excellent physicochemical properties, iron oxide (Fe2O3) has been extensively used in the fields of environmental pollution control and solar energy conversion. However, the high recombination rate of the photoinduced electron-hole pairs and poor charge mobility for Fe2O3 nanomaterial generally result in low photocatalytic efficiency. Herein, an uniform CdS nanorods grown directly on one-dimensional α-Fe2O3 nanotube arrays (NTAs) are successfully synthesized by a facile hydrothermal method and the constructed heterojunction can be a kind of efficient and recyclable photocatalysts. Successful deposition of CdS nanorods onto the α-Fe2O3 NTAs is verified by field emission scanning electron microscopy(FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS). UV-Vis diffuse reflectance spectroscopy indicates that α-Fe2O3/CdS NTAs possess the intense visible light absorption and also display a red-shift of the band-edge compared with the pure α-Fe2O3 NTAs. The as-obtained α-Fe2O3/CdS NTAs display excellent photocatalytic activity for decomposition of methylene blue (MB), methyl orange (MO), and phenol under visible light illumination. Among all the tested photocatalysts, the film synthesized for 3h with good stability exhibits the best photocatalytic properties and produces the highest photocurrent of 1.43 mA/cm2 at 0.8 V vs. Ag/AgCl electrode, owing to its well formed heterojunction structure, effective electron-hole pair separation and direct electron transfer pathway along the CdS nanorods and α-Fe2O3 NTAs. Besides, the photogenerated holes (h+) and superoxide radicals (O2-) play dominant roles in the photocatalytic process. On the basis of the photocatalytic results and energy band diagram, the photocatalytic process mechanism is proposed. Considering the easy preparation and excellent performance, α-Fe2O3/CdS NTAs could be a promising and competitive visible-light-driven photocatalyst in the field of environment remediation.

In situ growth of self-supported and defect-engineered carbon nanotube networks on 316L stainless steel as binder-free supercapacitors

Self-supported and defect-engineered carbon nanotube networks directly grown on 316L stainless steel are used for binder-free supercapacitors. In situ growth of the carbon nanotube networks on 316L stainless steel is obtained through the chemical vaporization deposition and thermal treatment to generate various defects. The relationship between the microstructures of carbon nanotube networks and electrochemical characteristics is investigated. The as-prepared carbon nanotube networks are characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman analysis. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy tests are also carried out to evaluate their capacitive properties, suggesting that the electrochemical characteristics are significantly affected by annealing time. The carbon nanotube networks annealed at 500 0C for 2 h display high capacitance of 11 mF cm-2 and excellent cycling lifetime with capacitance retention ration 97% at the scan rate of 0.5 mA cm-2 for 5000 periods, which is attributed to the defect engineering increasing the defects of carbon nanotube networks, enhancing hydrophilic property and facilitating the transportation of electrolyte ions.