Bimetallic metal-organic frameworks for controlled catalytic graphitization of nanoporous carbons

Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e., bimetallic MOFs). The organic linkers that coordinate with cobalt ions tend to yield graphitic carbons after carbonization, unlike those bridging with zinc ions, due to the controlled catalytic graphitization by the cobalt nanoparticles. In this work, we demonstrate a feasible method to achieve nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization, and content of heteroatoms. The bimetallic-MOF-derived nanoporous carbon are systematically characterized, highlighting the importance of precisely controlling the properties of the carbon materials. This can be done by finely tuning the components in the bimetallic MOF precursors, and thus designing optimal carbon materials for specific applications

Nanoarchitectured Graphene-Based Supercapacitors for Next-Generation Energy-Storage Applications

Tremendous development in the field of portable electronics and hybrid electric vehicles has led to urgent and increasing demand in the field of high‐energy storage devices. In recent years, many research efforts have been made for the development of more efficient energy‐storage devices such as supercapacitors, batteries, and fuel cells. In particular, supercapacitors have great potential to meet the demands of both high energy density and power density in many advanced technologies. For the last half decade, graphene has attracted intense research interest for electrical double‐layer capacitor (EDLC) applications. The unique electronic, thermal, mechanical, and chemical characteristics of graphene, along with the intrinsic benefits of a carbon material, make it a promising candidate for supercapacitor applications. This Review focuses on recent research developments in graphene‐based supercapacitors, including doped graphene, activated graphene, graphene/metal oxide composites, graphene/polymer composites, and graphene‐based asymmetric supercapacitors. The challenges and prospects of graphene‐based supercapacitors are also discussed

Metal-Organic Framework-Derived Nanoporous Metal Oxides toward Supercapacitor Applications: Progress and Prospects

Transition metal oxides (TMOs) have attracted significant attention for energy storage applications such as supercapacitors due to their good electrical conductivity, high electrochemical response (by providing Faradaic reactions), low manufacturing costs, and easy processability. Despite exhibiting these attractive characteristics, the practical applications of TMOs for supercapacitors are still relatively limited. This is largely due to their continuous Faradaic reactions, which can lead to major changes or destruction of their structure as well phase changes (in some cases) during cycling, leading to the degradation in their capacitive performance over time. Hence, there is an immediate need to develop new synthesis methods, which will readily provide stable porous architectures, controlled phase, as well as useful control over dimensions (1-D, 2-D, and 3-D) of the metal oxides for improving their performance in supercapacitor applications. Since its discovery in late 1990s, metal-organic frameworks (MOFs) have influenced many fields of material science. In recent years, they have gained significant attention as precursors or templates for the derivation of porous metal oxide nanostructures and nanocomposites for next-generation supercapacitor applications. Even though these materials have widespread applications and have been widely studied in terms of their structural features and synthesis, it is still not clear how these materials will play an important role in the development of the supercapacitor field. In this review, we will summarize the recent developments in the field of MOF-derived porous metal oxide nanostructures and nanocomposites for supercapacitor applications. Furthermore, the current challenges along with the future trends and prospects in the application of these materials for supercapacitors will also be discussed

Rational design of coaxial structured carbon nanotube-manganese oxide (CNT-MnO2) for energy storage application

Recently, there has been great research interest in the development of composites (core-shell structures) of carbon nanotubes (CNTs) with metal oxides for improved electrochemical energy storage, photonics, electronics, catalysis, etc. Currently, the synthetic strategies for metal oxides/hydroxides are well established, but the development of core-shell structures by robust, cost-effective chemical methods is still a challenge. The main drawbacks for obtaining such electrodes are the very complex synthesis methods which ultimately result in high production costs. Alternatively, the solution based method offers the advantages of simple and cost effective synthesis, as well as being easy to scale up. Here, we report on the development of multi-walled carbon nanotube-manganese oxide (CNT-MnO2) core-shell structures. These samples were directly utilized for asymmetric supercapacitor (ASC) applications, where the CNT-MnO2 composite was used as the positive electrode and ZIF-8 (zeolitic imidazolate framework, ZIF) derived nanoporous carbon was used as the negative electrode. This unconventional ASC shows a high energy density of 20.44 W h kg(-1) and high power density of 16 kW kg(-1). The results demonstrate that these are efficient electrodes for supercapacitor application

Rational design of coaxial structured carbon nanotube-manganese oxide (CNT-MnO2) for energy storage application

Recently, there has been great research interest in the development of composites (core-shell structures) of carbon nanotubes (CNTs) with metal oxides for improved electrochemical energy storage, photonics, electronics, catalysis, etc. Currently, the synthetic strategies for metal oxides/hydroxides are well established, but the development of core-shell structures by robust, cost-effective chemical methods is still a challenge. The main drawbacks for obtaining such electrodes are the very complex synthesis methods which ultimately result in high production costs. Alternatively, the solution based method offers the advantages of simple and cost effective synthesis, as well as being easy to scale up. Here, we report on the development of multi-walled carbon nanotube-manganese oxide (CNT-MnO2) core-shell structures. These samples were directly utilized for asymmetric supercapacitor (ASC) applications, where the CNT-MnO2 composite was used as the positive electrode and ZIF-8 (zeolitic imidazolate framework, ZIF) derived nanoporous carbon was used as the negative electrode. This unconventional ASC shows a high energy density of 20.44 W h kg-1 and high power density of 16 kW kg-1. The results demonstrate that these are efficient electrodes for supercapacitor application

Chemical Preparation of Ferroelectric Mesoporous Barium Titanate Thin Films: Drastic Enhancement of Curie Temperature Induced by Mesopore-Derived Strain

Mesoporous barium titanate (BT) thin films are synthesized by a surfactant-assisted sol-gel method. The obtained mesoporous BT thin films show enhanced ferroelectricity due to the effective strains induced by mesopores. The Curie temperature (T-c) of the mesoporous BT reaches approximately 470 degrees C

Effect of Various Carbonization Temperatures on ZIF-67 Derived Nanoporous Carbons

Here we have prepared ZIF-67 derived nanoporous carbons (NPCs) under different carbonization temperatures ranging from 800 to 1000 °C, and investigated the effect of the temperature on the porous structure. Raman analysis confirms that the graphitic degree of the obtained samples increases as the applied carbonization temperature is increased. With the gradual increase of the graphitic degree, the surface area is decreased

Large-Scale Synthesis of Reduced Graphene Oxides with Uniformly Coated Polyaniline for Supercapacitor Applications

We report an effective route for the preparation of layered reduced graphene oxide (rGO) with uniformly coated polyaniline (PANI) layers. These nanocomposites are synthesized by chemical oxidative polymerization of aniline monomer in the presence of layered rGO. SEM, TEM, X-ray photoelectron spectroscopy (XPS), FTIR, and Raman spectroscopy analysis results demonstrated that reduced graphene oxide-polyaniline (rGO-PANI) nanocomposites are successfully synthesized. Because of synergistic effects, rGO-PANI nanocomposites prepared by this approach exhibit excellent capacitive performance with a high specific capacitance of 286Fg(-1) and high cycle reversibility of 94% after 2000cycles

Surfactant-assisted synthesis of nanoporous nickel sulfide flakes and their hybridization with reduced graphene oxides for supercapacitor applications

We report a simple soft-templating strategy for the synthesis of nanoporous crystalline nickel sulfide with two-dimensional (2-D) morphology. The nickel sulfide phases and morphologies are varied by changing the hydrothermal temperatures applied. Furthermore, the nanoporous nickel sulfide (PNS) flakes can be hybridized with reduced graphene oxide (rGO) sheets. As compared to bare PNS flakes, the PNS/rGO composite, containing 40% rGO, exhibits a superior electrochemical performance in terms of specific capacitance and cyclic stability. The specific capacitance of this composite is evaluated by a three-electrode system, and it shows the highest specific capacitance of 1312 F g(-1) at a scan rate of 5 mV s(-1). In addition, this composite is also assembled to form an asymmetric supercapacitor with zeolitic imidazolate framework (ZIF-8)-derived carbon as a negative electrode, which gives a highest specific capacitance of 47.85 F g(-1) at 2 A g(-1), a high energy density of 17.01 W h kg(-1), and a high power density of 10 kW kg(-1)