Guicheng Liu

Study on the synthesis and properties of LiV3O8 rechargeable lithium batteries cathode

A new simple synthetic method was employed to produce LiV3O8 compound in which LiOH, V2O5 and NH4OH were used as the starting reactants. At first, V2O5 reacted with LiOH and NH4OH in liquid solutions to obtain a compound containing Li and V, which was then calcined at 370, 450 and 550 degreesC for 8 h, respectively. The electrochemical properties of the LiV3O8 compound were studied by galvanostatic charge-discharge, and the highest capacity of 274 mAh g(-1) was obtained for the LiV3O8 compound calcined at 370 C in the range of 1.8-4.0 V. In the fifteenth cycle, its capacity remained 257 mAh g(-1). The inspections by X-ray diffraction and SEM indicated that different calcining temperatures resulted in different structure, which resulted in different discharge capacity

Dye-sensitized solar cells based on hierarchically structured porous TiO2 filled with nanoparticles

A new morphology of TiO2 photoanodes for N-719 dye-sensitized solar cells (DSCs) has been developed with enhanced power conversion performance. Strategies for the synthesis of hierarchically structured three-dimensionally ordered macroporous (HS-3DOM) TiO2 with controlled macropore sizes (ca. 85–155 nm) by using well-arrayed polymethyl methacrylate with different diameters as well as two kinds of photoanode films based on hierarchically structured porous TiO2 filled with nanoparticles have been demonstrated. DSCs based on a special TiO2 photoanode with a macropore size of 105 nm exhibited a current density (Jsc) of 20.6 mA cm−2 and a high photo-to-electrical energy conversion efficiency (η) of 9.7%. This high power conversion efficiency is ascribed to the special morphology of the TiO2 photoanode with high dye adsorption due to its ordered and open structures, and also its light scattering and charge collection efficiency.

A novel photoanode with high flexibility for fiber-shaped dye sensitized solar cells

A completely flexible fiber-shaped dye sensitized solar cell has been truly realized for the first time, due to a novel photoanode with a TiO2 micron-cone-nanowire array structure prepared by a simple two-step process. The TiO2 micron-cone array, made using an electrochemical method, is used as a frame for a novel photoanode, with its roots sinking deep down into a Ti wire substrate. The TiO2 nanowire array is coated onto the TiO2 micron-cone surface by a hydrothermal reaction to form a dye-adsorption layer to the enhance power conversion efficiency of the novel device. With a high dye-adsorption capacity and strong combination between the TiO2 micron-cone and Ti substrate, the minimum bending radius of the photoanode could reach 0.45 mm, and 96.6% retention of the initial conversion efficiency was obtained after bending 100 times.

Effect of metal catalyst on the mechanism of hydrogen spillover in three-dimensional covalent-organic frameworks*

Hydrogen spillover mechanism of metal-supported covalent-organic frameworks COF-105 is investigated by means of the density functional theory, and the effects of metal catalysts M4 (Pt4, Pd4, and Ni4) on the whole spillover process are systematically analyzed. These three metal catalysts exhibit several similar phenomena: (i) they prefer to deposit on the tetra (4-dihydroxyborylphenyl) silane (TBPS) cluster with surface-contacted configuration; (ii) only the H atoms at the bridge site can migrate to 2,3,6,7,10,11-hexahydroxy triphenylene (HHTP) and TBPS surfaces, and the migration process is an endothermic reaction and not stable; (iii) the introduction of M4 catalyst can greatly reduce the diffusion energy barrier of H atoms, which makes it easier for the H atoms to diffuse on the substrate surface. Differently, all of the H2 molecules spontaneously dissociate into H atoms onto Pt4 and Pd4 clusters. However, the adsorbed H2 molecules on Ni4 cluster show two types of adsorption states: one activated state with stretched H–H bond length of 0.88 A via the Kubas interaction and five dissociated states with separated hydrogen atoms. Among all the M4 catalysts, the orders of the binding energy of M4 deposited on the substrate and average chemisorption energy per H2 molecule are Pt4 >Ni4 >Pd4. On the contrary, the orders of the migration and diffusion barriers of H atoms are Pt4 <Ni4 <Pd4, which indicates that Pt4 is the most promising catalyst for the hydrogen spillover with the lowest migration and diffusion energy barriers. However, the migration of H atoms from Pt4 toward the substrate is still endothermic. Thus direct migration of H atom from metal catalyst toward the substrate is thermodynamically unfavorable.

Li4SiO4-Based Artificial Passivation Thin Film for Improving Interfacial Stability of Li Metal Anodes

An amorphous SiO2 (a-SiO2) thin film was developed as an artificial passivation layer to stabilize Li metal anodes during electrochemical reactions. The thin film was prepared using an electron cyclotron resonance-chemical vapor deposition apparatus. The obtained passivation layer has a hierarchical structure, which is composed of lithium silicide, lithiated silicon oxide, and a-SiO2. The thickness of the a-SiO2 passivation layer could be varied by changing the processing time, whereas that of the lithium silicide and lithiated silicon oxide layers was almost constant. During cycling, the surface of the a-SiO2 passivation layer is converted into lithium silicate (Li4SiO4), and the portion of Li4SiO4 depends on the thickness of a-SiO2. A minimum overpotential of 21.7 mV was observed at the Li metal electrode at a current density of 3 mA cm-2 with flat voltage profiles, when an a-SiO2 passivation layer of 92.5 nm was used. The Li metal with this optimized thin passivation layer also showed the lowest charge-transfer resistance (3.948 Ω cm) and the highest Li ion diffusivity (7.06 × 10-14 cm2 s-1) after cycling in a Li-S battery. The existence of the Li4SiO4 artificial passivation layer prevents the corrosion of Li metal by suppressing Li dendritic growth and improving the ionic conductivity, which contribute to the low charge-transfer resistance and high Li ion diffusivity of the electrode.

Reconstruction method of Magneto-acoustic Tomography with magnetic Induction

The inverse problem of magneto-acoustic tomography with magnetic induction (MAT-MI) includes: (1) reconstruction of secondary magnetic field from the divergence of Lorentz force density; (2) resistivity reconstruction from the secondary magnetic field. Numerical simulations are performed to test the algorithm.

ZnO Nanorod Array Modified PVDF Membrane with Superhydrophobic Surface for Vacuum Membrane Distillation Application

The vacuum membrane distillation (VMD) is a promising technology for lots of applications. To solve the membrane fouling and wetting problems, in this paper, a novel ZnO nanorods 1 H,1 H,2 H,2 H-perfluorodecyltriethoxysilane (PDTS) modified poly(vinylidene fluoride) (PVDF) membrane with a micro/nanoscale hierarchical structure and a superhydrophobic surface has been prepared and applied to the VMD process for distilling highly salty water, for the first time. Among these, a pyrolysis-adhesion method is created to obtain the ZnO seeds and fasten them on the PVDF substrate firmly. The novel modified membrane shows a stable superhydrophobic surface with a water contact angle of 152°, easy cleaning property, excellent thermal and mechanical stability, because of the Cassies state caused by pocketing much air in the hydrophobized ZnO nanorods, the low surface energy of PDTS coating, and the strong adhesion between ZnO nanorods and PVDF membrane, which has built an ideal structure for VMD application. After 8 h VMD of 200 g L-1 NaCl solution, compared to the virgin PVDF membrane, the novel membrane shows a similar permeate flux but a much higher quality permeated liquid because of its unique antifouling and antiwetting caused by the several microns gap between the feed and the membrane. Due to its easy cleaning property, the novel membrane also exhibits an excellent reusability.

Self-Relaxant Superelastic Matrix Derived from C60 Incorporated Sn Nanoparticles for Ultra-High-Performance Li-Ion Batteries

Homogeneously dispersed Sn nanoparticles approximately ⩽10 nm in a polymerized C60 (PC60) matrix, employed as the anode of a Li-ion battery, are prepared using plasma-assisted thermal evaporation coupled by chemical vapor deposition. The self-relaxant superelastic characteristics of the PC60 possess the ability to absorb the stress-strain generated by the Sn nanoparticles and can thus alleviate the problem of their extreme volume changes. Meanwhile, well-dispersed dot-like Sn nanoparticles, which are surrounded by a thin SnO2 layer, have suitable interparticle spacing and multilayer structures for alleviating the aggregation of Sn nanoparticles during repeated cycles. The Ohmic characteristic and the built-in electric field formed in the interparticle junction play important roles in enhancing the diffusion and transport rate of Li ions. SPC-50, a Sn-PC60 anode consisting of 50 wt % Sn and 50 wt % PC60, as confirmed by energy-dispersive X-ray spectroscopy analysis, exhibited the highest electrochemical performance. The resulting SPC-50 anode, in a half-cell configuration, exhibited an excellent capacity retention of 97.18%, even after 5000 cycles at a current density of 1000 mA g-1 with a discharge capacity of 834.25 mAh g-1. In addition, the rate-capability performance of this SPC-50 half-cell exhibited a discharge capacity of 544.33 mAh g-1 at a high current density of 10 000 mA g-1, even after the current density was increased 100-fold. Moreover, a very high discharge capacity of 1040.09 mAh g-1 was achieved with a capacity retention of 98.67% after 50 cycles at a current density of 100 mA g-1. Futhermore, a SPC-50 full-cell containing the LiCoO2 cathode exhibited a discharge capacity of 801.04 mAh g-1 and an areal capacity of 1.57 mAh cm-2 with a capacity retention of 95.27% after 350 cycles at a current density of 1000 mA g-1.

Low-Temperature Synthesis of Near-Monodisperse Globular MoS2 Nanoparticles with Sulphur Powders

Nanoparticles (NPs) with high uniformity have been extensively investigated for their excellent chemical stability. Near-monodisperse globular MoS2 NPs were prepared with sulphur powders (SPs) as a sulphur source by a one-pot polyol-mediated process without surfactants, transfer agents and toxic agents at 170–190∘C. The as-processed SPs greatly affected the formation of the MoS2 NPs after low-activity sulphur (S8)n was reassembled from common SPs (S8). The average size of MoS2 NPs can be reduced remarkably from 100–200nm to 50nm by introducing low amounts of MnCl2. A preliminary four-step growth mechanism based on the aggregation-coalescence model was also proposed. This green and simple method may be an alternative to the common hot-injection and heating-up methods for the preparation of monodisperse NPs, particularly transition metal dichalogenides.

Reconstruction algorithm of Inductive Magnetic Resonance Electrical Impedance Tomography

A theoretical study on reconstruction algorithm of 1D inductive magnetic resonance electrical impedance tomography (IMREIT) is given by this paper. The computequation of the inverse problem are proposed by using the concentric disc model. Numerical simulation are performed to tes the algorithm for both noise-free and noisy cases, and the results show the correctness of the method. It can be as the theoretical basic for the future study on IMREIT.