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

Facile “Scratching” Method with Common Metal Objects To Generate Large-Scale Catalyst Patterns Used for Growth of Single-Walled Carbon Nanotubes

A facile “scratching” method to pattern a catalyst with commonly used metal objects, such as blade, pen cover, tweezers, watchband, knife, key, clamp, and coin, was developed. The single-walled carbon nanotube (SWCNT) networks and well-aligned SWCNT arrays successfully grew by chemical vapor deposition on the scratched catalyst patterns on Si/SiOx and quartz, respectively. This method provides an extremely simple and nearly zero-cost way to fabricate large-scale catalyst patterns used for controlled growth of SWCNT arrays, which could have potential applications in the fabrication of CNT-based devices

Transparent, Flexible, All-Reduced Graphene Oxide Thin Film Transistors

Owing to their unique thickness-dependent electronic properties, together with perfect flexibility and transparency, graphene and its relatives make fantastic material for use in both active channel and electrodes in various electronic devices. On the other hand, the electronic sensors based on graphene show high potential in detection of both chemical and biological species with high sensitivity. In this contribution, we report the fabrication of all-reduced graphene oxide (rGO) thin film transistors by a combination of solution-processed rGO electrodes with a micropatterned rGO channel, and then study their applications in biosensing. Our all-rGO devices are cost-effective, highly reproducible, and reliable. The fabricated electronic sensor is perfectly flexible with high transparency, showing good sensitivity in detecting proteins in the physiological buffer. As a proof of concept, fibronectin as low as 0.5 nM was successfully detected, which is comparable with the previously reported protein sensors based on single-layer pristine graphene obtained from mechanical cleavage. The specific detection of avidin by using biotinylated all-rGO sensor is also successfully demonstrated

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

Gram-Scale Preparation of 2D Transition Metal Hydroxide/Oxide Assembled Structures for Oxygen Evolution and Zn-Air Battery

Construction of 2D materials into a hierarchical structure cannot only effectively avoid restacking of individual nanosheets but also endows them with improved catalytic efficiency, which have generated extensive interest in recent years. Nevertheless, the scalable and effective preparation of 2D materials constructed hierarchical structures, such as unique 2D/1D structure, is rarely achieved. Herein, we report a facile alkali-soaking strategy for the preparation of 2D transition metal hydroxide/oxide nanosheets-assembled hierarchical structures, in which the rational designed bimetallic metal–organic frameworks (MOFs) are annealed followed by a simple alkali soaking. Our method is capable of preparing various hierarchical structures based on 2D materials, including Co­(OH)2, Ni­(OH)2, and Mn3O4 nanosheets. Moreover, a high yield of ∼2.2 g was achieved for a batch of Co­(OH)2 nanosheet-assembled structure. Impressively, the as-synthesized Co­(OH)2 hierarchical structure shows excellent electrocatalytic performances toward the oxygen evolution reaction (OER), which achieves a current density of 10 mA cm–2 at a low overpotential of 267 mV with a small Tafel slope of 62.0 mV dec–1. Furthermore, it delivers a small charging/discharging voltage gap of 1.2 V at 75 mA cm–2 and high stability for over 240 h, when used as an air cathode for rechargeable Zn-air batteries

Toward Ultralong Lifespan Aqueous Zinc-Ion Batteries via Sulfur-Defect Vanadium Tetrasulfide Cathode

Vanadium sulfide has become one of the promising cathodes of aqueous rechargeable zinc-ion batteries (AZIBs); however, the further application of vanadium sulfides for AZIBs is severely restricted by the limited specific capacity and poor cycling stability. Herein, we synthesize the vanadium tetrasulfide nanosphere with S-defects and coated by an ultrathin carbon layer (D-VS4). The as-assembled Zn//D-VS4 cell delivers a high specific capacity of 295 mAh g–1 at 0.5 A g–1 and long-time cycling stability (a capacity retention of 72.0% after 8,000 cycles). The electrochemical reaction mechanism of D-VS4 is revealed. This work provides a significant supplement to the study of vanadium-based sulfides cathode for AZIBs

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

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

Data_Sheet_1_Bimetallic Metal-Organic Framework-Derived Carbon Nanotube-Based Frameworks for Enhanced Capacitive Deionization and Zn-Air Battery.pdf

Carbon-based materials have attracted intensive attentions for a wide range of energy and environment-related applications. Energy storage/conversion devices with improved performance have been achieved by utilization of metal-organic-framework (MOF)-derived carbon structures as active materials in recent years. However, the effects of MOF precursors on the performance of derived carbon materials are rarely investigated. Here, we report that the incorporation of small amount of Fe or Ni in Co-based MOFs leads to a significant enhancement for the derived carbon nanotube-based frameworks (CNTFs) in Na+/Cl− ion electrosorption. Further investigation revealed the enhanced performance can be attributed to the improved specific surface area, electrical conductivity, and electrochemical activity. Notably, the CoFe-CNTF derived from bimetallic CoFe-MOFs achieves a high ion adsorption capacity of 37.0 mg g−1, superior to most of recently reported carbon-based materials. Furthermore, the CoFe-CNTF also demonstrates high catalytic activity toward oxygen evolution reaction (OER) with a Tafel slope of 87.7 mV dec−1. After combination with three-dimensional graphene foam (3DG), the resultant CoFe-CNTF-coated 3DG is used as air-cathode to fabricate a flexible all-solid-state Zn-air battery, which exhibits a high open circuit potential of 1.455 V. Importantly, the fabricated flexible battery can light a light-emitting diode (LED) even when it is bent. This work provides new insights into designs of high-performance and flexible electrode based on MOF-derived materials.</p