JingBing Liu

Preparation of Novel Three-Dimensional NiO/Ultrathin Derived Graphene Hybrid for Supercapacitor Applications

A new type of three-dimensional (3D) NiO/ultrathin derived graphene (UDG) hybrid on commercial Ni foam (NF) for a binder-free pseudocapacitor electrode is presented. NiO nanoflakes are in situ grown by a chemical bath deposition (CBD) technique on the free-standing 3D UDG/NF scaffold, which is first prepared by a simple nanocasting process consisting of hydrothermal reaction and subsequent thermal transformation. The 3D UDG/NF scaffold with interconnected network affords a high conductivity due to the high graphitization degree and efficiently facilitates the electron transport to NiO. Moreover, the 3D NiO/UDG/NF hybrid allows for a thinner 3D active material layer under the same loading density, which could shorten the diffusion paths of ions. The NiO/UDG/NF hybrid is directly used as a binder-free supercapacitor electrode, which exhibited significantly improved supercapacitor performance compared to the bare CBD prepared NiO/NF electrode.

Self-assembly of hydroxyapatite nanostructures by microwave irradiation

Hydroxyapatite (HAp) nanorods, bowknot-like nanostructures and flower-like architectures have been directly synthesized and assembled under microwave irradiation without the help of any templates. The uniform nanorods present an average diameter of about 40 nm and a length of up to about 400 nm. The as-prepared bowknot-like nanostructures consist of sword-like HAp nanorods with a typical width of 150 nm and lengths up to 1–2 µm. The flower-like architectures are composed of leaf-like flakes with typical diameters of 150–200 nm and lengths up to 1–2 µm. The SAED and HRTEM experiments imply that the sword-like HAp nanorods and leaf-like flakes are single crystalline in nature and preferentially grow along the [001] direction. It is found that the pH value and the complex reagent EDTA play important roles in synthesis of the final HAp nanostructures. The possible mechanism is discussed for the formation of the HAp nanostructures in the presence of EDTA under microwave irradiation.

Novel non-hydrazine solution processing of earth-abundant Cu2ZnSn(S,Se)4 absorbers for thin-film solar cells

A novel non-hydrazine precursor solution followed by dip-coating has been developed to produce Cu2ZnSnS4 (CZTS) and Cu2ZnSn(S,Se)4 (CZTSSe) thin films. The precursor solution is based on an ethanol solution of metal–thioacetamide (TAA) complex with monoethanolamine (MEA) as the additive agent. By forming coordination complexes with TAA, metal cations are found to have good solubility in ethanol–MEA solvents, producing molecular-level blending in metal precursor solutions. All the materials are low-cost and environmentally friendly. The annealing treatments are conducted under vacuum and Se vapor to form CZTS and CZTSSe absorber films. A solar cell fabricated with the CZTSSe thin film exhibits power conversion efficiency of 5.36%, which is much higher than that (2.86%) of the cell using the CZTS thin film as absorber.

One-step approach to novel Bi4V2O11 hierarchical hollow microspheres with high visible-light-driven photocatalytic activities

New visible-light-sensitive hierarchical Bi4V2O11 hollow microspheres have been successfully synthesized by a facile template-free solvothermal route. The hierarchical Bi4V2O11 superstructure was constructed of single-crystalline nanoplates with a porous surface. A possible growth pattern and formation mechanism of hierarchical Bi4V2O11 hollow microspheres was proposed. The Brunauer–Emmett–Teller (BET) surface area of the hollow sample was 84.613 m2 g−1, which was much higher than other prepared Bi4V2O11 powders. The hierarchical Bi4V2O11 hollow microspheres exhibited excellent visible-light-driven photocatalytic activity for the degradation of Rhodamine-B (RhB). The improved photocatalytic performance could be ascribed to the high specific surface area, the narrow band gap and unique hierarchical hollow structure. The resulting hierarchical Bi4V2O11 hollow microspheres are very promising photocatalysts for degrading organic pollutants and other applications.

Three-dimensional Co3O4/flocculent graphene hybrid on Ni foam for supercapacitor applications

A novel Co3O4/flocculent graphene (FG) hybrid on commercial Ni foam (NF) has been prepared. The unique flocculent graphene structure is prepared by combining a rapid filtering approach through Ni foam and a template method, in which the thermally expanded graphite is used as precursor and polystyrene (PS) microspheres are used as templates. The PS spheres play an important role in preventing the re-stacking of graphene nanosheets and the formation of flocculent graphene on NF. The PS spheres were first introduced as a guest material and were subsequently removed by calcination. The resulting free-standing FG/NF provides a three-dimensional and high conductivity scaffold for the hydrothermal growth of Co3O4 nanoclusters. The obtained Co3O4/FG/NF hybrid could be directly used as a binder-free supercapacitor electrode. Moreover, the Co3O4 nanoclusters on FG/NF scaffold exhibit improved specific capacitance of 1615 F g−1 compared to that of the bare NF. The 3D active material layer of Co3O4/FG/NF hybrid, high conductivity of 3D FG/NF scaffold and functional features of the Co3O4 nanocluster morphology synergistically result in an improved electrochemical performance.

Research Progress in Improving the Rate Performance of LiFePO4 Cathode Materials

Olivine lithium iron phosphate (LiFePO4) is considered as a promising cathode material for high power-density lithium ion battery due to its high capacity, long cycle life, environmental friendly, low cost, and safety consideration. The theoretical capacity of LiFePO4 based on one electron reaction is 170 mAh g−1 at the stable voltage plateau of 3.5 V vs. Li/Li+. However, the instinct drawbacks of olivine structure induce a poor rate performance, resulting from the low lithium ion diffusion rate and low electronic conductivity. In this review, we summarize the methods for enhancing the rate performance of LiFePO4 cathode materials, including carbon coating, elements doping, preparation of nanosized materials, porous materials and composites, etc. Meanwhile, the advantages and disadvantages of above methods are also discussed.

Reaction routes for the formation of a Cu2ZnSnS4 absorber material from homogenous ethanol-based solution

Solution-based deposition processes have taken a leading role in producing high efficiency devices from Cu2ZnSnS4 (CZTS) systems. The Cu2ZnSn(S,Se)4 (CZTSSe) films deposited from our ethanol-based process currently provide a high reported efficiency for this material system at 5.36%. In this paper, we report a detailed study of the ethanol-based solution deposition route from the chemistry occurring in the precursor solution to the transformation from solid state framework to the CZTS phase during a subsequent annealing treatment. The homogenous CZTS precursor solution is a mixture of three different metal–thioacetamide (TAA) complexes, which has been proven by the analysis of UV-vis-near-IR absorption spectra and FT-IR absorption spectra. X-ray diffraction (XRD) and Raman spectroscopy have been employed to track every stage of the reaction route. It is found that the complexes build up an ordered framework upon drying and transform to a CuSn3.75S8 phase and finally to the CZTS phase after subsequent annealing treatments. The relative simplicity of this formation mechanism is beneficial for the performance of the CZTS based solar cells.

Preparation of Pb1-xLaxTi1-x/4O3 (x = 0.28) powders by a sol-gel-hydrothermal method

Abstract Pseudocubic Pb 1− x La x Ti 1− x /4 O 3 (PLT, x =0.28) powders were prepared by a sol–gel-hydrothermal method using KOH as mineralizer. Characterization via X-ray diffraction and Raman spectroscopy indicate that, KOH mineralizer plays two important roles in this work. First, it favors the crystallization of PLT; second, it promotes La to be solved in the lattice which consequently resulted in the phase transition from tetragonal structure to pseudocubic structure.

Hydrothermal synthesis of strontium bismuth tantalate powder

Abstract A hydrothermal process has been carried out to synthesize perovskite-type strontium bismuth tantalate (SBT) powder simply by reacting Sr(CH 3 COOH) 2 and Bi 2 O 3 with Ta 2 O 5 . The results of Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) indicate that submicron size of pyrochlore-free SBT powders could be obtained at a low temperature of 220 °C by using 10 M KOH as mineralizer. It is suggested that KOH mineralizer plays important roles in favoring the crystallization of as-obtained products, and promoting the formation of perovskite SBT.

Improvement on optical modulation and stability of the NiO based electrochromic devices by nanocrystalline modified nanocomb hybrid structure

Among the explored materials for electrochromic devices (ECDs), nickel oxide thin films have been widely applied as an optical anodic layer due to its ability to adjust the optical properties by ion exchange. Generally, to realize the three important characters including color contrast, switch speed and cycling durability, it requires the electrochromic layer to possess different microstructures or crystalline properties. Thus there is still difficulty in designing a suitable structure for NiO film to have excellent electrochromic performance. Here, a nanocrystalline modified nanocomb novel NiO structure is prepared by a simple chemical process. This novel microstructure shows highly multiple channels, high surface areas and good crystallinity. All of these characters produce a good electrochromic performance including fast switch speed (around 2 s), high color contrast (69.4%) and in company with good cycling durability (more than 1000 cycles). This simple chemical process demonstrated here could be suitable for the large scale production of future electrochromic device applications.