Liwei Mi

Cation Exchange Induced Tunable Properties of a Nanoporous Octanuclear Cu(II) Wheel with Double-Helical Structure

A double-helical octanuclear Cu(II) wheel 1 with 2.88 nm diameter was prepared through the reaction of a clinical medicine, telmisartan, with copper sulfate. Central copper ions can be partially replaced by bivalent zinc and cobalt ions and fully exchanged by trivalent iron ions. The properties of central metal ion-exchanged variants are much different from those of 1. Central metal ion exchange might be regarded as a powerful and effective method to modify properties from one crystalline material to another only by varying central metal ions under moderate conditions.

Double Metal Ions Synergistic Effect in Hierarchical Multiple Sulfide Microflowers for Enhanced Supercapacitor Performance

In this paper, the design, synthesis, and measurement of a new and hierarchically structured series of NixCo1-xS1.097 electroactive materials are reported. The materials were synthesized through an ion-exchange process using hierarchically structured CoS1.097 as precursors, and a strategy utilizing the synergistic effect of double metal ions was developed. Two complementary metal ions were used to enhance the performance of electrode materials. The specific capacitance of the electroactive materials was continuously improved by increasing the nickel ion content, and the electric conductivity was also enhanced when the cobalt ion was varied. Experimental results showed that the nickel ion content in NixCo1-xS1.097 could be adjusted from x = 0 to 0.48. Specifically, when x = 0.48, the composite exhibited a remarkable maximum specific capacitance approximately 5 times higher than that of the CoS1.097 precursors at a current density of 0.5 A g(-1). Furthermore, the specific capacitance of Ni0.48Co0.52S1.097 electrodes that were modified with reduced graphene oxide could reach to 1152 and 971 F g(-1) at current densities of 0.5 and 20 A g(-1) and showed remarkably higher electrochemical performance than the unmodified electrodes because of their enhanced electrical conductivity. Thus, the strategy utilizing the synergistic effect of double metal ions is an alternative technique to fabricate high-performance electrode materials for supercapacitors and lithium ion batteries.

Hybrid solar cells with outstanding short-circuit currents based on a room temperature soft-chemical strategy: the case of P3HT:Ag2S.

P3HT:Ag(2)S hybrid solar cells with broad absorption from the UV to NIR band were directly fabricated on ITO glass by using a room temperature, low energy consumption, and low-cost soft-chemical strategy. The resulting Ag(2)S nanosheet arrays facilitate the construction of a perfect percolation structure with organic P3HT to form ordered bulk heterojunctions (BHJ); without interface modification, the assembled P3HT:Ag(2)S device exhibits outstanding short-circuit current densities (J(sc)) around 20 mA cm(-2). At the current stage, the optimized device exhibited a power conversion efficiency of 2.04%.

Three-dimensional CuS hierarchical architectures as recyclable catalysts for dye decolorization

In the current paper, we report the synthesis of three-dimensional (3D) copper sulfide (CuS) with novel tertiary hierarchical architectures prepared by a one-step solvothermal method through the reaction of sulfur powder and solid copper for the first time. In this work, porous copper foam is used as the template. In this material, the primary structure is the multi-structure interchange copper foam precursor, the secondary structure is 10–20 μm cubic solids, and the tertiary structure is interpenetrating flakes with a thickness of 40–50 nm. Owing to the obtained hierarchical structure, the CuS material grows firmly in situ on a 3D copper template. This stable 3D framework will make the recycling of the material into a heterogeneous catalyst facile. This catalyst shows highly efficient heterogeneous catalytic properties in degrading dye-containing solutions, such as methylene blue (MB), rhodamine B (RB), and their mixed solution. The 3D structure of Fenton-like CuS catalysts plays an important role in the degradation process of MB and RB solvents with the help of H2O2 which can yield highly reactive hydroxyl radicals. This catalyst is easy to recycle, and it can be used as a degrading catalyst in highly concentrated dye wastewater because of its low cost, simple operation, and highly efficient properties.

A nest-like Ni@Ni1.4Co1.6S2 electrode for flexible high-performance rolling supercapacitor device design

Herein we fabricated a series of flexible electrode materials with nickel foam as a partly self-sacrificial template by an in situ growth solvent thermal method. We synthesized a nest-like Ni@Ni3S2 electrode material with building blocks of ∼80 nm diameter nanowires. The growth mechanism of nest-like Ni@Ni3S2 electrode materials was studied through time-dependent experiments, in which the control of material morphology was realized. Residual metal nickel in the framework bestows the as-obtained electrode materials with excellent flexibility. The nest-like Ni@Ni1.4Co1.6S2 electrode material with a similar morphology and structure to Ni@Ni3S2 was fabricated using the Ni@Ni3S2 material as the template by a Co-exchange method. Continuous transition from Ni3S2 to Co9S8 was achieved depending on different replacement times. The synergistic and complementary advantageous effects of Co and Ni ions enhanced the specific capacitances from 89 F g−1 (Ni@Ni3S2) to 122 F g−1 (Ni@Ni1.4Co1.6S2) at a current density of 1 A g−1 at a high loading level of ∼20 mg cm−2. Moreover, the cycle stability and coulombic efficiency of the Ni@Ni3S2 electrode material were also increased by the introduction of Co ions. All the as-assembled Ni@Ni3S2 and Ni@Ni1.4Co1.6S2//activated carbon supercapacitor devices possessed high energy and power density, suggesting their potential application in high-performance flexible asymmetric rolling supercapacitor devices.

Synergistic effect induced ultrafine SnO2/graphene nanocomposite as an advanced lithium/sodium-ion batteries anode

SnO2/graphene materials have received extensive attention in broad applications owning to their excellent performances. However, multi-step and harsh synthetic methods with high temperatures and high pressures are major obstacles that need to be overcome. Herein a simple, low-cost, and scalable approach is proposed to construct ultrafine SnO2/graphene nanomaterials effectively under constant pressure and at the low temperature of 80 °C for 4 h, in which ultrafine SnO2 nanoparticles grow on graphene sheets uniformly and firmly via Sn–O–C bonding. This result depends on the synergetic effect of two reactions, the reduction of graphene oxide and formation of SnO2 nanoparticles, which are achieved successfully. More importantly, the constructed SnO2/graphene material exhibits excellent electrochemical properties in both lithium-ion batteries and sodium-ion batteries. As an anode material for lithium-ion batteries, it displays a high reversible capacity (1420 mA h g−1 at 0.1 A g−1 after 90 cycles) and good cycling life (97% at 1 A g−1 after 230 cycles), whereas in sodium-ion batteries, it maintains a capacity of 1280 mA h g−1 at 0.05 A g−1 and 650 mA h g−1 at 0.2 A g−1 after 90 cycles. The proposed synthetic methodology paves the way for the effective and large scale preparation of graphene-based composites for broad applications such as energy storage, optoelectronic devices, and catalysis.

3D hierarchically patterned tubular NiSe with nano-/microstructures for Li ion battery design

Tubular nickel selenide (NiSe) crystals with hierarchical structures were successfully fabricated using a one-step solvothermal method in moderate conditions, in which ethylenediamine and ethylene glycol were used as the mixed solvent. The growth of hierarchical NiSe microtubes from NiSe microflakes was achieved without surfactants or other chemical additives by changing the reaction time. When the as-synthesized NiSe microtubes were employed as cathode materials for lithium-ion batteries, the initial discharge capacity of hierarchical NiSe microtubes reached 410.7 mAh g(-1).

Pyrite FeS2 microspheres anchoring on reduced graphene oxide aerogel as an enhanced electrode material for sodium-ion batteries

Pyrite, FeS2, is a promising sodium battery electrode candidate owing to its abundance in natural resources; however, it suffers from poor cyclic performance and poor rate performance, which hinders its large-scale commercial application. The semiconductor nature of pyrite as well as the dissolution of polysulfide and the destruction of the morphology of pyrite during the charge/discharge process are the main reasons for the abovementioned two drawbacks. In this study, a well-designed FeS2/rGO-A composite was constructed using an ambient temperature reaction. The introduction of rGO-A improved the conductivity of the entire material without hindering sodium ion diffusion; it also confined the pulverized active material to prevent its loss. Additionally, by controlling the cutoff voltage above 0.8 V, the formation of polysulfide was avoided. As a result, the FeS2/rGO-A electrode displays both excellent cyclic performance (low decay rate of 0.051% per cycle over 800 cycles at 1C) and rate performance (more than 70% discharge capacity is retained at 5C compared to 0.1C). The unique electrochemical mechanism was also investigated in detail. A new perspective of pyrite electrochemical behavior was obtained. This study provides not only a theoretical basis for further study, but may also enable the large-scale commercial application of sodium-ion batteries.

Large-scale urchin-like micro/nano-structured NiS: controlled synthesis, cation exchange and lithium-ion battery applications

Large-scale uniform urchin-like nickel sulfide (NiS) was successfully synthesized by a solvothermal method under moderate conditions. A mixture of ethylenediamine and ethylene glycol was used as solvent. A complex obtained using a simple method was used as a precursor. Based on the results for nickel sulfide (NiS), multiple sulfides were synthesized by a method based on morphology and replication. Outstanding features were obtained such as composition regulation, i.e., the main physical properties of the product can be adjusted under mild conditions without changing the morphology. Multiple sulfides were synthesized through ion-exchange reaction to achieve morphology transfer. The products were assembled as cathode materials for lithium-ion batteries to test discharge/charge performance. The first discharge/charge performance ranged from 314.8 to 597.3 mAh g−1. This result indicated that the composition and performance of the materials can be regulated by changing the central metal ion without changing the morphology.

Controlled synthesis of 3D hierarchical NiSe microspheres for high-performance supercapacitor design

In this work, hierarchical nanosheet-based NiSe microspheres were successfully fabricated using a facile one-step solvothermal method, in which ethylenediamine and N,N-dimethylformamide were used as the mixed solvent. The evolution of this morphology and the effects of cetyltrimethylammonium bromide were also explored. The as-synthesized NiSe microspheres exhibited the ideal performance when employed as electrode materials of supercapacitors.