A New Type of Porous Graphite Foams and Their Integrated Composites with Oxide/Polymer Core/Shell Nanowires for Supercapacitors: Structural Design, Fabrication, and Full Supercapacitor Demonstrations

We attempt to meet the general design requirements for high-performance supercapacitor electrodes by combining the strategies of lightweight substrate, porous nanostructure design, and conductivity modification. We fabricate a new type of 3D porous and thin graphite foams (GF) and use as the light and conductive substrates for the growth of metal oxide core/shell nanowire arrays to form integrated electrodes. The nanowire core is Co₃O₄, and the shell is a composite of conducting polymer (poly­(3,4-ethylenedioxythiophene), PEDOT) and metal oxide (MnO₂). To show the advantage of this integrated electrode design (viz., GF + Co₃O₄/PEDOT–MnO₂ core/shell nanowire arrays), three other different less-integrated electrodes are also prepared for comparison. Full supercapacitor devices based on the GF + Co₃O₄/PEDOT–MnO₂ as positive electrodes exhibit the best performance compared to other three counterparts due to an optimal design of structure and a synergistic effect

Vapor–Liquid–Solid Growth of Endotaxial Semiconductor Nanowires

Free-standing and in-plane lateral nanowires (NWs) grown by the vapor–liquid–solid (VLS) process have been widely reported. Herein, we demonstrate that the VLS method can be extended to the synthesis of horizontally aligned semiconductor NWs embedded in substrates. Endotaxial SiGe NWs were grown in silicon substrates by tuning the directional movement of the catalyst in the substrates. The location of the SiGe NWs can be controlled by the SiO₂ pattern on the silicon surface. By varying the growth conditions, the proportion of Ge in the obtained NWs can also be tuned. This approach opens up an opportunity for the spatial control of the NW growth in substrates and can potentially broaden the applications of NWs in new advanced fields

Controlled Synthesis of Carbon-Coated Cobalt Sulfide Nanostructures in Oil Phase with Enhanced Li Storage Performances

A novel solvothermal process was developed for the synthesis of carbon-coated Co₉S₈ nanodandelions using 1-dodecanethiol as the sulfur source and the soft template. Replacing 1-dodecanethiol with sulfur powder as the sulfur source leads to the formation of 20 nm Co₉S₈ nanoparticles without carbon coating. When tested as LIB anode, the C@Co₉S₈ dandelion delivers a specific capacity of 520 mA h g^–1 at a current density of 1 A g^–1 (1.8 <i>C</i>) during the 50th cycle, which is much higher than that of Co₉S₈ nanoparticles (e.g. 338 mA h g^–1). Furthermore, the C@Co₉S₈ dandelion also exhibits excellent high <i>C</i>-rate performance, e.g., depicts a 10th-cycle capacity of 373 mA h g^–1 at a current density of 6 A g^–1 (10.9 <i>C</i>), which is better than that of many reported anode materials. Such synthesis approach is attractive for the preparation of sulfide anode materials with high Li storage properties

Synthesis of Two-Dimensional CoS_1.097/Nitrogen-Doped Carbon Nanocomposites Using Metal–Organic Framework Nanosheets as Precursors for Supercapacitor Application

Two-dimensional (2D) metal–organic framework (MOF) nanosheets are attracting increasing research interest. Here, for the first time, we report the facile synthesis of 2D porphyrin paddlewheel framework-3 (PPF-3) MOF nanosheets with thickness of ca. 12–43 nm. Through the simultaneous sulfidation and carbonization of PPF-3 MOF nanosheets, we have prepared the 2D nanocomposite of CoS_1.097 nanoparticles (NPs) and nitrogen-doped carbon, referred to as CoSNC, in which the CoS_1.097 NPs with size of ca. 10 nm are embedded in the nitrogen-doped carbon matrix. As a proof-of-concept application, the obtained 2D CoSNC nanocomposite is used as an electrode material for a supercapacitor, which exhibits a specific capacitance of 360.1 F g^–1 at a current density of 1.5 A g^–1. Moreover, the composite electrode also shows high rate capability. Its specific capacitance delivered at a current density of 30.0 A g^–1 retains 56.8% of the value at 1.5 A g^–1

High-Performance Membrane Capacitive Deionization Based on Metal−Organic Framework-Derived Hierarchical Carbon Structures

Membrane capacitive deionization (MCDI) is a simple and highly energy efficient method to convert brackish water to clean water. In this work, a high-performance MCDI electrode architecture, which is composed of three-dimensional graphene networks and metal–organic frameworks (MOFs)–derived porous carbon rods, was prepared by a facile method. The obtained electrode material possesses not only the conducting networks for rapid electron transport but also the short diffusion length of ions, which exhibits excellent desalination performance with a high salt removal capacity, i.e., 37.6 mg g^–1 at 1.2 V in 1000 mg L^–1 NaCl solution. This strategy can be extended to other MOF-derived MCDI electrodes

Facile Fabrication of Three-Dimensional Graphene and Metal–Organic Framework Composites and Their Derivatives for Flexible All-Solid-State Supercapacitors

A facile and general method for the large-scale preparation of various three-dimensional (3D) graphene oxide/metal–organic framework (GO/MOF) composites is developed through a simple mixing process using MOFs and graphene oxide. This preparation method is able to rapidly produce GO/MOF composite hydrogels with controllable composition in only several minutes, which is also suitable to a series of different MOFs. The obtained GO/MOF composites are severed as the precursors for the subsequent preparation of MOF-derived composite aerogels, e.g., rGO/Fe₂O₃ and rGO/NiO/Ni composite aerogels, through freeze-dry and calcination processes. When used as a supercapacitor electrode, the rGO/Fe₂O₃ composite shows a good rate capability with high specific capacitances of 869.2 and 289.6 F·g^–1 at the current densities of 1 and 20 A·g^–1, respectively, as well as a long cycle life without obvious decrease of capacitance after 5000 cycles. Moreover, the flexible all-solid-state supercapacitor device is also fabricated based on the obtained rGO/Fe₂O₃ composite aerogel, which exhibits a high volumetric capacitance of 250 mF·cm^–3 at 6.4 mA·cm^–3 and a capacity retention of 96.3% after 5000 cycles at 50.4 mA·cm^–3, as well as an excellent mechanical flexibility