Xiao Chen

One dimensional MnO2/titanium nitride nanotube coaxial arrays for high performance electrochemical capacitive energy storage

One dimensional MnO2/titanium nitride nanotube coaxial arrays have been designed for a high performance electrochemical capacitive energy storage system based on the concept of fabricating an efficient, fast charge separation network. This nanostructured composite material was prepared by electrodepositing mesoporous MnO2 into TiN nanotube arrays (TiN NTA), which are prepared by anodization of a Ti foil substrate and subsequent nitridation using ammonia annealing. The electrodeposited mesoporous MnO2 inside the electrically conductive framework of a TiN nanotube has been found to show high specific capacitance (681.0 F g−1 at 2 A g−1), excellent rate capability (55% capacitance retention from 2 to 2000 mV s−1), and a long cycle life (3% capacitance loss after 1000 cycles). These results demonstrate that this coaxial composite nanostructure is very promising for high performance supercapacitors.

Mesoporous Coaxial Titanium Nitride-Vanadium Nitride Fibers of Core–shell Structures for High-Performance Supercapacitors

In this study, titanium nitride-vanadium nitride fibers of core-shell structures were prepared by the coaxial electrospinning, and subsequently annealed in the ammonia for supercapacitor applications. These core-shell (TiN-VN) fibers incorporated mesoporous structure into high electronic conducting transition nitride hybrids, which combined higher specific capacitance of VN and better rate capability of TiN. These hybrids exhibited higher specific capacitance (2 mV s(-1), 247.5 F g(-1)) and better rate capability (50 mV s(-1), 160.8 F g(-1)), which promise a good candidate for high-performance supercapacitors. It was also revealed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) characterization that the minor capacitance fade originated from the surface oxidation of VN and TiN.

Facile Preparation of Mesoporous Titanium Nitride Microspheres for Electrochemical Energy Storage

In this study, mesoporous TiN spheres with tunable diameter have been fabricated via a facile template-free strategy. Under ammonia atmosphere, mesoporous TiO₂ spheres are directly converted into mesoporous TiN spheres with the addition of cyanamide to retain the original morphology. The electrochemical performance of the resultant mesoporous TiN spheres demonstrates that this material can be a promising electrode material for nonaqueous supercapacitors with high energy densities.

Molybdenum nitride based hybrid cathode for rechargeable lithium-O2 batteries

Molybdenum nitride/nitrogen-doped graphene nanosheets (MoN/NGS) are synthesized and used as an alternative O(2) electrode for Li-O(2) batteries. In comparison with electrocatalysts proposed previously, this hybrid cathode exhibits a high discharge potential (around 3.1 V) and a considerable specific capacity (1490 mA h g(-1), based on carbon + electrocatalyst).

Nanostructured Titanium Nitride/PEDOT:PSS Composite Films As Counter Electrodes of Dye-Sensitized Solar Cells

The composite films of titanium nitride in conjunction with polystyrenesulfonate-doped poly (3,4-ethylene-dioxythiophene) (PEDOT:PSS) were prepared by a simple mechanical mixture of TiN and PEDOT:PSS under ultrasonication, which was demonstrated to deliver an effectively combined network of both high electrical conductivity and superior electrocatalytic activity. The composite films have been explored as an alternative for the counter electrodes of dye-sensitized solar cells. It was manifested that these nanostructured TiN-PEDOT:PSS composite films displayed excellent performance comparable to Pt-FTO counter electrode due to the combined network endowing more favorable and efficient interfacial active sites. Among them, the energy conversion efficiency of the cell with TiN(P)-PEDOT:PSS as counter electrode reached 7.06%, which was superior to 6.57% of the cell with Pt-FTO counter electrode under the same experimental conditions.

Vapour-based processing of hole-conductor-free CH3NH3PbI3 perovskite/C-60 fullerene planar solar cells

A new sequential-vapour-deposition method is demonstrated for the growth of high-quality CH3NH3PbI3 perovskite films. This has enabled the all-vapour, low-temperature fabrication of hole-conductor-free planar perovskite solar cells consisting of only a CH3NH3PbI3/C60 bi-layer sandwiched between two electrical contacts, with a power conversion efficiency of 5.4%.

Molybdenum nitride/n-doped carbon nanospheres for lithium-o2 battery cathode electrocatalyst.

Molybdenum nitride/N-doped carbon nanospheres (MoN/N-C) are synthesized by hydrothermal method followed by ammonia annealing. The as-prepared MoN/N-C nanospheres manifest considerable electrocatalytic activity toward oxygen reduction reaction in nonaqueous electrolytes because of its nanostructure and the synergetic effect between MoN and N-C. Furthermore, the MoN/N-C nanospheres are explored as cathode catalyst for Li-O2 batteries with tetra-(ethylene glycol) dimethyl ether as the electrolyte. The assembled batteries deliver alleviated overpotentials and improved battery lifespan, and their excellent performances should be attributed to the unique hierarchical structure and high fraction of surface active sites of cathode catalyst.

Compatible interface design of CoO-based Li-O 2 battery cathodes with long-cycling stability

Lithium-oxygen batteries with high theoretical energy densities have great potential. Recent studies have focused on different cathode architecture design to address poor cycling performance, while the impact of interface stability on cathode side has been barely reported. In this study, we introduce CoO mesoporous spheres into cathode, where the growth of crystalline discharge products (Li2O2) is directly observed on the CoO surface from aberration-corrected STEM. This CoO based cathode demonstrates more than 300 discharge/charge cycles with excessive lithium anode. Under deep discharge/charge, CoO cathode exhibited superior cycle performance than that of Co3O4 with similar nanostructure. This improved cycle performance can be ascribed to a more favorable adsorption configuration of Li2O2 intermediates (LiO2) on CoO surface, which is demonstrated through DFT calculation. The favorable adsorption of LiO2 plays an important role in the enhanced cycle performance, which reduced the contact of LiO2 to carbon materials and further alleviated the side reactions during charge process. This compatible interface design may provide an effective approach in protecting carbon-based cathodes in metal-oxygen batteries.

Hierarchical micro/nano-structured titanium nitride spheres as a high-performance counter electrode for a dye-sensitized solar cell

Hierarchical micro/nano-structured TiN spheres (micro/nano-TiNs) counter electrodes are fabricated by coating hierarchical micro/nano-TiO2 paste onto Ti foil followed by a nitridation reaction. Compared with particulate TiN and TiN flat electrodes, the as-prepared hierarchical micro/nano-TiNs electrode based dye-sensitized solar cells (DSCs) delivers significantly improved photovoltaic performances due to the presence of the hierarchical structure. In particular, VOC is enhanced by about 60 mV, which may be predominantly attributed to the gaining of favourable interfacial active sites and the traces of N-doped carbon residues. After an initial optimization of the particle sizes of the hierarchical micro/nano-TiNs, the reflectance effect of large submicroscale particles is attempted to improve the ISC. The highest overall conversion efficiency yields 7.83%, which is 30% higher than that of Pt/FTO (6.04%).

DNA optical sensor: a rapid method for the detection of DNA hybridization

A DNA optical sensor system is proposed based on the combination of sandwich solution hybridization, magnetic bead capture, flow injection and chemiluminescence for rapid detection of DNA hybridization. Bacterial alkaline phosphatase (phoA) gene and Hepatitis B virus (HBV) DNA were used as target DNA. A biotinylated DNA probe was used to capture the target gene onto the streptavidin-coated magnetic beads and a calf intestine alkaline phosphatase (CAP)-labelled DNA probe was used for subsequent enzymatic chemiluminescence detection. The detection cycle was less than 30 min, excluding the DNA hybridization time, which was about 100 min. Both the phoA gene and HBV DNA could be detected at picogramme or femtomole level. No response signal was obtained when target DNA did not exist in the sample. Successive sample detection could be made by removing the magnetic field and a washing step.