Yuanhao Wang

Preparation and lithium storage performance of yolk–shell Si@void@C nanocomposites

Yolk-shell Si@void@C nanocomposites are prepared via a facile method of resorcinol-formaldehyde coating and LiOH etching, without SiO2 pre-modification on Si particles, expensive carbon sources, or environmentally-unfriendly HF solutions. Profiting from these favorable features, Si@void@C nanocomposites exhibit considerable reversible capacities (628 mA h g(-1) after 100 cycles) and good rate performances.

Three-dimensional double deck meshlike dye-sensitized solar cells

In this paper, we develop a new type of three-dimensional dye-sensitized solar cells (3D DSSCs) with double deck cylindrical Ti meshes as the substrates. One of the Ti meshes is anodized to in situ synthesize the self-organized TiO2 nanotube layer as the photoanode materials. Another Ti mesh is platinized through electrodeposition as the counter electrode. The morphologies of the electrodes are characterized by scanning electron microscopy. We investigate the effect of the mesh number on the 3D DSSCs with the dye adsorption, cyclic voltammetry, and electrochemical impedance spectroscopy. The results show that with the increase in the mesh number, the dye-loadings on the photoanode and the active surface area of Pt on the counter electrode are increased, while the diffusion of the electrolyte becomes more difficult due to the reduced diameter of the openings in the mesh. It has also been demonstrated that the performance of this 3D DSSC is independent of the incident solar beam angle due to its axial symme...

Multi-yolk–shell SnO2/Co3Sn2@C Nanocubes with High Initial Coulombic Efficiency and Oxygen Reutilization for Lithium Storage

The challenging problems of SnO2 anode material for lithium ion batteries are the poor electronic conductivity and the low oxygen reutilization due to the irreversibility of Li2O generated in the initial discharge leading to a theoretical initial Coulombic efficiency (ICE) of only 52.4%. Different from these strategies, this work proposes a novel strategy to level up the oxygen reutilization in SnO2 by introducing Co3Sn2 nanoalloys which can release Co atoms to reversibly react with Li2O instead. According to this protocol, multi-yolk-shell SnO2/Co3Sn2@C nanocubes are designed and successfully prepared using hollow CoSn(OH)6 nanocubes as precursors followed a hydrothermal carbon coating and calcination treatment. The unique multi-yolk-shell nanostructure offers adequate breathing space for the volumetric deformation during long-term cycling. Moreover, the removal of Li2O allows a high electronic conductivity and resultant rate performance. As a result, the efficient reutilization of oxygen enables a high ICE of 71.7% and a reversible capacity of 1003 mA h g-1 after 200 cycles at 100 mA g-1. Cyclic voltammetry, cycling performance at different voltage windows, and X-ray photoelectron spectroscopy confirm the proposed mechanism. This strategy employing oxygen-poor metals or alloys provides a novel approach to enhance the oxygen reutilization in SnO2 for higher reversibility.

Hierarchical CoMoO4@Co3O4 nanocomposites on an ordered macro-porous electrode plate as a multi-dimensional electrode in high-performance supercapacitors

Nanoscale core–shell CoMoO4@Co3O4 composite materials are fabricated by a multi-step hydrothermal process on the surface and side wall of an ordered macro-porous electrode plate (OMEP) as the active electrode in a high power density storage device. The morphology, formation mechanism of the CoMoO4@Co3O4 nanostructure, and capacitor performance are systematically studied. The CoMoO4@Co3O4/OMEP electrode has a capacity of 7.13 F cm−2 (1168.0 F g−1) at a constant current density of 0.6 A g−1 and a retention ratio of 81.4% after 5000 cycles. The large specific capacitance and excellent rate capability can be attributed to the unique 3D ordered porous architecture which facilitates electron and ion transport, enlarges the liquid–solid interfacial area, prevents agglomeration of nanomaterials, and boosts the utilization efficiency of the active materials. Reconstruction on the surface of the porous structured substrate enhances the power density and cycling performance at large current densities. Using the CoMoO4@Co3O4/OMEP electrode as the positive electrode and active carbon/nickel foam (AC/NF) as the negative electrode, the electrochemical electrode packaged in a CR2025 battery cell as a miniature hybrid device exhibits stable power characteristics (10u2006000 cycles with 91.7% retention at a current of 0.1 A). The device produces large instantaneous power that charging it for 10 s and using three devices in series can power four parallel LED arrays at a current of 0.152 A.

Building self-ordered tubular macro- and mesoporous nitridated titania from gas bubbles towards high-performance lithium-ion batteries

Robust well-defined tubular structural materials based on macro- and mesoporous nitridated titania (TMMN-TiO2) were obtained by a simple solution-phase approach in ammonia solution. In this approach, the gas bubbles derived from ammonia solution play the role of templates that direct the ordered growth in the form of a tubular structure. The results demonstrated that the volume ratio of ammonia to water can be favorable for the formation of TMMN-TiO2, which are characterized by FESEM and FTIR. What is more, ammonia was used not only as the template but also as the nitrogen source. Interestingly, it was found that the TiO2 nanocrystals building blocks were assembled into an interconnected mesoporous skeleton and built in ordered tubular macroporous channels. This unique architecture provides many important features that are required for high-performance anodes, such as fast ion transport, high conductivity, and structure stability, thus enabling an electrode with outstanding lithium storage performance. For example, such an electrode delivers 112 mA h g(-1) capacity at 5100 mA g(-1) (30 C) even after 1200 cycles.

Nanoparticles-aided silver front contact paste for crystalline silicon solar cells

High-dispersive spherical silver nanoparticles were prepared by solvothemal process, using ethylene glycol as solvent and reducing agent. The silver nanoparticles were characterized by X-ray diffraction and FESEM to analyze the size, shape and morphology. X-Ray diffraction (XRD) pattern indicated that the silver nanoparticles were well-crystallized with no crystallographic impurities. The average size calculated by Debye–scherrer’s fomula was 48xa0nm, which well agreed with the result of FESEM. From the FESEM, it was demonstrated that the silver nanoparticles were high-dispersive and spherical in shape. Thick silver films were prepared by screen-printing using the front contact silver paste containing the as-prepared silver nanoparticles. The experimental results indicated that the silver nanoparticles were favor to sintering of micro-size silver particles, and contributed to improve the photovoltaic performances of crystalline silicon solar cells.

Development of high dispersed TiO2 paste for transparent screen-printable self-cleaning coatings on glass

This paper reports a cheap and facile method to fabricate transparent self-cleaning coatings on glass by screen-printing high dispersed TiO2 paste. Three kinds of ZrO2 beads with diameter of 2, 1, and 0.1–0.2xa0mm were utilized to investigate their influence on the grinding and dispersion of the commercial TiO2 powder in the ball mill. From the SEM images, surface profiler and transmittance spectrum it could be demonstrated that the smallest ZrO2 bead with the diameter of 0.1–0.2xa0mm was the best candidate to disperse the TiO2 powder into nanoscale size to make the high dispersed TiO2 paste which was the key factor to achieve a smooth, high transparent TiO2 coating. The surface wettability measurement showed that all the screen-printed coatings had super hydrophilic surfaces, which was independent to the surface morphology. However, the coating with the highest transparency showed the lowest photocatalytic activity which is mainly due to the light loss.

Water-Soluble Polymeric Interfacial Material for Planar Perovskite Solar Cells

Interfacial materials play a critical role in photoelectric conversion properties as well as the anomalous hysteresis phenomenon of the perovskite solar cells (PSCs). In this article, a water-soluble polythiophene PTEBS was employed as a cathode interfacial material for PSCs. Efficient energy level aligning and improved film morphology were obtained due to an ultrathin coating of PTEBS. Better ohmic contact between the perovskite layer and the cathode also benefits the charge transport and extraction of the device. Moreover, less charge accumulation at the interface weakens the polarization of the perovskite resulting in a relatively quick response of the modified device. The ITO/PTEBS/CH3NH3PbI3/spiro-MeOTAD/Au cells by an all low-temperature process achieved power conversion efficiencies of up to 15.4% without apparent hysteresis effect. Consequently, the utilization of this water-soluble polythiophene is a practical approach for the fabrication of highly efficient, large-area, and low-cost PSCs and compatible with low-temperature solution process, roll-to-roll manufacture, and flexible application.

Experimental study of the flow characteristics in a falling film liquid desiccant dehumidifier

The flow characteristics play great role in determining the heat and mass transfer performance of a falling film liquid desiccant dehumidifier. Even though there have been many studies reporting the flow behaviors in different devices and fields, the fundamental researches of the film flow characteristics in a liquid desiccant dehumidifier were still very limited, especially for experiment. Therefore, in the present work, a simple single-channel test rig was established for observing and describing the flow characteristics in the dehumidifier. The impacts of various variables on the flow morphology, coverage ratio, and minimum wetting rate have been analyzed in detail. A correlation was developed to predict the minimum wetting rate of the solution flow. The research results can further verify the correctness of a previous simulation work as well.

EG-Assisted synthesis and electrochemical performance of ultrathin carbon-coated LiMnPO 4 nanoplates as cathodes in lithium ion batteries

Ultrathin carbon-coated LiMnPO4 (ULMP/C) nanoplates were prepared through an ethylene glycol- (EG-) assisted pyrolysis method. Different from most of LiMnPO4/Cworks, the obtained ULMP/C possessed relatively small particle size (less than 50nm in thickness) and preferable carbon coating (∼1nmin thickness, 2wt.%). As a reference, LiMnPO4/C (LMP/C) composites were also fabricated via the traditional hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TG), galvanostatic charge-discharge, and cyclic voltammetry (CV) were performed to characterize the crystalline phase, morphology, structure, carbon content, and electrochemical behaviors of samples. The electrochemical performance of bare and carbon-coated LiMnPO4 was evaluated as cathodes in lithium ion batteries. As a result, the obtained ULMP/C nanoplates demonstrated much higher reversible capacities (110.9mAhg-1 after 50 cycles at 0.1 C) and rate performances than pure LMP and LMP/C composites. This facile and efficient EG-assisted pyrolysis method can enlighten us on exploiting advanced routes to modify active materials with ultrathin and homogeneous carbon layers.