SnO x /graphene anode material with multiple oxidation states for high-performance Li-ion batteries.

Tin and its oxides are promising anode materials owing to their high theoretical capacity, rich resource, and environmental benignity. To achieve low cost and green synthesis, a facile synthetic route of SnO x /graphene composites is proposed, using a simple galvanic replacement method to quickly obtain abundant foamed tin as raw material and ball milling method to realize a mechanochemical reaction between SnO x (0 ≤ x ≤ 2) and graphene. Under different annealing conditions, the foamed tin is converted to tin oxides with multiple oxidation states (Sn3O4, SnO, and SnO2). These unique components can greatly affect the electrochemical performance of the electrode in LIBs. The as-prepared electrode (SnO x -300/G) obtained by annealing foamed tin at 300 °C for 4 h and combining SnO x powders with graphene via ball milling shows great cycling stability, retaining a high capacity of 786 mA h g-1 at 0.1 A g-1 after 150 cycles, and its initial Coulombic efficiency can reach 84.03%. Thus, this facile synthesis can provide an environmentally friendly route for commercial production of high-performance energy storage materials.

One-Step In Situ Self-Assembly of Cypress Leaf-Like Cu(OH)2 Nanostructure/Graphene Nanosheets Composite with Excellent Cycling Stability for Supercapacitors.

Transition metal hydroxides and graphene composite holds great promise to be the next generation of high performance electrode material for energy storage applications. Here we fabricate the cypress leaf-like Cu(OH)2 nanostructure/graphene nanosheets composite through one-step in situ synthesis process, employed as a new type of electrode material for high efficiency electrochemical energy storage in supercapacitors. A solution-based two-electrode system is applied to synthesize Cu(OH)2/graphene hybrid nanostructure, where anodic graphene nanosheets firmly anchor cathodic Cu(OH)2 nanostructure due to the electrostatic interaction. The in situ self-assembly of Cu(OH)2/graphene ensures good structural robustness and the cypress leaf-like Cu(OH)2 nanostructure prompt to form the open and porous morphology. The hybrid structure would facilitate charge transport and effectively mitigate the volume changes during long-term charging/discharging cycles. As a consequence, the Cu(OH)2/graphene composite exhibits the highest capacitance of 317 mF/cm2 at the current density of 1 mA/cm2 and superior cyclic stability with no capacitance decay over 20,000 cycles and remarkable rate capability at increased current densities.

NiO/Ni x Co3-x O4 porous ultrathin nanosheet/nanowire composite structures as high-performance supercapacitor electrodes.

The demand for a new generation of high-safety, long-lifespan, and high-capacity power sources increases rapidly with the growth of energy consumption in the world. Here we report a facile method for preparing architecture materials made of NiO/Ni x Co3-x O4 porous nanosheets coupled with NiO/Ni x Co3-x O4 porous nanowires grown in situ on nickel foams using a hydrothermal method without any binder followed by a heat treatment process. The nanosheet-shaped NiO/Ni x Co3-x O4 species in the nanosheet matrix function well as a scaffold and support for the dispersion of the Ni x Co3-x O4 nanowires, resulting in a relatively loose and open structure within the electrode matrix. Among all composite electrodes prepared, the one annealed in air at 300 °C displays the best electrochemical behavior, achieving a specific capacitance of 270 mF cm-2 at 5 mA cm-2 while maintaining excellent stability (retaining ≈ 89% of the max capacitance after 20 000 cycles), demonstrating its potential for practical application in power storage devices.

A one-step method to fabricate novel three-dimensional GaP nanopore arrays for enhanced photoelectrochemical hydrogen production.

Gallium phosphide nanopore arrays with unique three-dimensional interior architectures (3D GaP NPs) are fabricated by electrochemical etching in a neutral solution. As the photoanodes for photoelectrochemical (PEC) hydrogen production, the 3D GaP NPs exhibited a larger photocurrent density (5.65 mA cm-2 at 0 V vs. RHE, which is 58.3 and 2.3 times as large as that of the planar wafer and the NPs reported by our group in our previous work respectively) and a lower onset potential (-0.58 V vs. RHE, shifting negatively nearly 300 mV compared with its counterparts in the previous work). Besides the excellent light-trapping characteristics of the nanostructures, electrochemical impedance spectroscopy (EIS) further confirmed that the enhanced PEC performance was ascribed to the more efficient charge separation and transfer, and the increased surface area with the unique 3D NP arrays. Furthermore, the efficient charge separation may be attributed to the passivated surface states by the neutral solution.

Galvanic displacement assembly of ultrathin Co3O4 nanosheet arrays on nickel foam for a high-performance supercapacitor.

High-performance supercapacitors are very desirable for many portable electronic devices, electric vehicles and high-power electronic devices. Herein, a facile and binder-free synthesis method, galvanic displacement of the precursor followed by heat treatment, is used to fabricate ultrathin Co3O4 nanosheet arrays on nickel foam substrate. When used as a supercapacitor electrode the prepared Co3O4 on nickel foam exhibits a maximum specific capacitance of 1095 F g-1 at a current density of 1 A g-1 and good cycling stability of 71% retention after 2000 cycling tests. This excellent electrochemical performance can be ascribed to the high specific surface area of each Co3O4 nanosheet that comprises numerous nanoparticles.