Yigang Chen

Three-dimensional self-branching anatase TiO2 nanorods: morphology control, growth mechanism and dye-sensitized solar cell application

Complex three-dimensional (3D) hierarchical nanostructures based on well-defined low-dimensional nanobranches of different sizes and specific exposed facets are highly desirable to obtain tunable physicochemical properties. Herein, a facile, one-step hydrothermal method is employed to construct self-branching anatase TiO2 (SBAT) 3D hierarchical nanostructures. By simply controlling the reaction time and weight ratio of F127/TBAH, SBAT nanorods can be obtained with a large percentage of exposed {010} facets. Based on X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis, a growth mechanism is proposed for the formation of such self-branching 3D nanostructures, which involves the formation of the L-shaped step edges on the [103] surfaces and the alignment of the crystal facets (103) of anatase nanocrystals with the (103) face on the tips of the main anatase TiO2 nanorods. The dye-sensitized solar cell assembled with the SBAT nanorods exhibits an outstanding power conversion efficiency of 7.17%, which is superior to that of the devices based on the 1D anatase TiO2 nanorods and P25 TiO2. This high performance can be attributed to the high dye-uptake density, large size and unique self-branching 3D hierarchical nanostructures built from 1D nanobranches growing epitaxially from the main rod.

Effects of Ag-ion implantation on the performance of DSSCs with a tri-layer TiO2 film

Tri-layer titania films were doped with Ag ions using MEVVA (metal vapor vacuum arc) ion-implantation, and characterized for photovoltaic performance in dye-sensitized solar cells (DSSCs). The current density was significantly improved with the increasing numbers of implanted Ag-ions. The highest energy-efficiency of 5.85% was achieved for the modified DSSCs by Ag-ion implantation with 1 × 1016 atom per cm−2. The enhancement effect of Ag-ion implantation on photoelectric performance of the DSSCs contributed toward the decrease in charge-transfer resistance and enhancement of dye adsorption. In addition, the Ag-doping induced an impurity level, which reduces the recombination rate of electrons and positively shifts the conduction band edge of titania to match the LUMO level of the dye.

Influence of magnetic fields on the morphology and pseudocapacitive properties of NiO on nickel foam

Nanostructured nickel oxide (NiO) films have been successfully deposited on nickel foam by a simple magnetic-field-assisted hydrothermal method, followed by calcination in air. The NiO thin films consisted of uniformly hexagonal nanoplates when magnetic fields (0–12.6 mT) were applied through an electromagnetic coil. The magnetic field affected the size and growth direction of NiO nanoplates, as well as the electrochemical performance of the NiO nanomaterial. The magnetic-field-assisted NiO electrodes showed better electrochemical performance than the NiO electrode synthesized without a magnetic field. The optimal NiO electrode had a specific capacitance of 932.1 F g−1 at 0.5 A g−1, with a retention ratio of 91.9% at 2.0 A g−1 over 1000 cycles. These results indicated that the magnetic-field-assisted method in the hydrothermal synthesis of NiO electrodes could be an economical and effective way to produce high-performance supercapacitors.