Highly Porous Metal-Organic Framework Entrapped by Cobalt Telluride-Manganese Telluride as an Efficient Bifunctional Electrocatalyst.

The electrochemical conversion of oxygen holds great promise in the development of sustainable energy for various applications, such as water electrolysis, regenerative fuel cells, and rechargeable metal-air batteries. Oxygen electrocatalysts are needed that are both highly efficient and affordable, since they can serve as alternatives to costly precious-metal-based catalysts. This aspect is particularly significant for their practical implementation on a large scale in the future. Herein, highly porous polyhedron-entrapped metal-organic framework (MOF)-assisted CoTe2/MnTe2 heterostructure one-dimensional nanorods were initially synthesized using a simple hydrothermal strategy and then transformed into ZIF-67 followed by tellurization which was used as a bifunctional electrocatalyst for both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The designed MOF CoTe2/MnTe2 nanorod electrocatalyst exhibited superior activity for both OER (η = 220 mV@ 10 mA cm-2) and ORR (E1/2 = 0.81 V vs RHE) and outstanding stability. The exceptional achievement could be primarily credited to the porous structure, interconnected designs, and deliberately created deficiencies that enhanced the electrocatalytic activity for the OER/ORR. This improvement was predominantly due to the enhanced electrochemical surface area and charge transfer inherent in the materials. Therefore, this simple and cost-effective method can be used to produce highly active bifunctional oxygen electrocatalysts.

Synergistic Performance Boosts of Dopamine-Derived Carbon Shell Over Bi-metallic Sulfide: A Promising Advancement for High-Performance Lithium-Ion Battery Anodes.

A CoMoS composite is synthesized to combine the benefits of cobalt and molybdenum sulfides as an anodic material for advanced lithium-ion batteries (LIBs). The synthesis is accomplished using a simple two-step hydrothermal method and the resulting CoMoS nanocomposites are subsequently encapsulated in a carbonized polydopamine shell. The synthesis procedure exploited the self-polymerization ability of dopamine to create nitrogen-doped carbon-coated cobalt molybdenum sulfide, denoted as CoMoS@NC. Notably, the de-lithiation capacity of CoMoS and CoMoS@NC is 420 and 709 mAh g⁻1, respectively, even after 100 lithiation/de-lithiation cycles at a current density of 200 mA g⁻1. Furthermore, excellent capacity retention ability is observed for CoMoS@NC as it withstood 600 consecutive lithiation/de-lithiation cycles with 94% capacity retention. Moreover, a LIB full-cell assembly incorporating the CoMoS@NC anode and an NMC-532 cathode is subjected to comprehensive electrochemical and practical tests to evaluate the performance of the anode. In addition, the density functional theory showcases the increased lithium adsorption for CoMoS@NC, supporting the experimental findings. Hence, the use of dopamine as a nitrogen-doped carbon shell enhanced the performance of the CoMoS nanocomposites in experimental and theoretical tests, positioning the material as a strong candidate for LIB anode.

(Fe-Co-Ni-Zn)-Based Metal-Organic Framework-Derived Electrocatalyst for Zinc-Air Batteries.

Zinc-air batteries (ZABs) have garnered significant interest as a viable substitute for lithium-ion batteries (LIBs), primarily due to their impressive energy density and low cost. However, the efficacy of zinc-air batteries is heavily dependent on electrocatalysts, which play a vital role in enhancing reaction efficiency and stability. This scholarly review article highlights the crucial significance of electrocatalysts in zinc-air batteries and explores the rationale behind employing Fe-Co-Ni-Zn-based metal-organic framework (MOF)-derived hybrid materials as potential electrocatalysts. These MOF-derived electrocatalysts offer advantages such as abundancy, high catalytic activity, tunability, and structural stability. Various synthesis methods and characterization techniques are employed to optimize the properties of MOF-derived electrocatalysts. Such electrocatalysts exhibit excellent catalytic activity, stability, and selectivity, making them suitable for applications in ZABs. Furthermore, they demonstrate notable capabilities in the realm of ZABs, encompassing elevated energy density, efficacy, and prolonged longevity. It is imperative to continue extensively researching and developing this area to propel the advancement of ZAB technology forward and pave the way for its practical implementation across diverse fields.

Activated carbon derived from cherry flower biowaste with a self-doped heteroatom and large specific surface area for supercapacitor and sodium-ion battery applications.

Herein, cherry flower waste-derived activated carbon (CFAC) with self-doped nitrogen is synthesized as a viable energy storage material for green and sustainable energy solutions. The activated carbon derived in this way is examined as an electric double-layer capacitance (EDLC)-type electrode material and sodium-ion battery (NIB) electrode material, and commendable performance is demonstrated for both of these energy storage applications. The specific surface area (SSA) and nitrogen content are observed to play a very delicate role in determining the charge storage ability of the CFAC, and the performance is optimized only by carefully balancing both of these properties. The optimized CFAC electrode supplied an excellent performance with a specific capacitance of 333.8 F g-1 and capacity is maintained to more than 96% even after 38,000 charge-discharge cycles as an EDLC-type supercapacitor electrode material. Likewise, the CFAC/NIB also yielded remarkable performance with an average specific capacity of 150 mAh g-1 and capacity retention of more than 84% after 200 charge-discharge cycles. Furthermore, an electrokinetic study was performed for both supercapacitor and NIB applications to identify the contribution from surface and diffusion type charge storage phenomena, consequently highlighting the role of the SSA and nitrogen content in the CFAC matrix.

Homogeneous Elongation of N-Doped CNTs over Nano-Fibrillated Hollow-Carbon-Nanofiber: Mass and Charge Balance in Asymmetric Supercapacitors Is No Longer Problematic.

The hurdle of fabricating asymmetric supercapacitor (ASC) devices using a faradic cathode and a double layer anode is challenging due to the required large amount of active mass of anodic material compared to that of the cathodic material during mass balancing due to the large difference in capacitance values of the two electrodes. Here, the problem is addressed by engineering a negative electrode that furnishes an ultrahigh capacitance. An in situ developed metal-organic framework (MOF)-based thermal treatment is adopted to grow highly porous N-doped carbon nanotubes (CNTs) containing submerged Co nanoparticles over nano-fibrillated electrospun hollow carbon nanofibers (HCNFs). The optimized CNT@HCNF-1.5 furnishes an ultrahigh capacitance approaching 712 F g-1 with excellent rate capability. The capacitance reported from this work is the highest for any carbonaceous material reported to date. The CNT@HCNF-1.5 is further used to fabricate symmetric supercapacitors (SSCs), as well as ASC devices. Remarkably, both the SSC and ASC devices furnish incredible performances in all aspects of SCs, such as a high energy density, long cycle life, and high rate capability, displaying decent practical applicability. The energy density of the SSC device reaches as high as 20.13 W h kg-1 , whereas that of ASC approaches 87.5 W h kg-1 .

Polypyrrole Nanotunnels with Luminal and Abluminal Layered Double Hydroxide Nanosheets Grown on a Carbon Cloth for Energy Storage Applications.

The structural design of transition metal-based electrode materials with gigantic energy storage capabilities is a crucial task. In this work, we report an assembly of thin layered double hydroxide (LDH) nanosheets arrayed throughout the luminal and abluminal parts of polypyrrole tunnels fastened onto both sides of a carbon cloth as a battery-type energy storage system. Electron microscopy images reveal that the resulting electrode (NiCo-LDH@H-PPy@CC, where H-PPy@CC represents carbon cloth-supported hollow polypyrrole fibers) is constructed by combining luminal and abluminal NiCo-LDH nanosheets onto a long polypyrrole tunnel on a carbon cloth. The primary sample shows an excellent specific capacity of 149.16 mAh g-1 at 1.0 mA cm-2, a remarkable rate capability of 80.45%, and comprehensive cyclic stability (93.4%). The improved performance is mainly attributed to the strategic organization of the electrode materials with superior Brunauer-Emmett-Teller (BET) surface area and conductivity. Moreover, an asymmetric supercapacitor device assembled with NiCo-LDH@H-PPy@CC and vanadium phosphate-incorporated carbon nanofiber (VPO@CNFs900) electrodes contributes a specific energy density of 32.42 Wh kg-1 at 3 mA cm-2 with a specific power density of 359.16 W kg-1. When the current density is increased by 6-fold, the specific power density reaches 1999.89 W kg-1 at a specific energy density of 20.06 Wh kg-1. This is a simple, cost-effective, and convenient synthetic strategy for the synthesis of porous nanosheet arrays assimilated into hollow fiber architectures, which can illuminate the ideal approach for the fabrication of novel materials with an immense potential for energy storage.

Metal-organic framework assisted vanadium oxide nanorods as efficient electrode materials for water oxidation.

The water oxidation process, which comprises the oxygen evolution reaction (OER), is a critical catalytic mechanism for sustainable technologies like water electrolysis and fuel cells. Herein, we develop a unique metal-organic framework aided vanadium pentoxide nanorods (MOF-V2O5 NRs-500) that can be used as an OER electrocatalyst under alkaline solutions. The crystal structure, surface chemical state, and porosity of MOF-V2O5 NRs-500 can be altered by annealing in an oxygen atmosphere. The resultant MOF-V2O5 NRs-500 demonstrate high catalytic activity against OER in basic conditions, with a low overpotential of 300 mV at a derived current density of 50 mA cm-2, and extraordinary durability of more than 50 h. Superior electrochemical performance might be attributed to the high exposure level of active sites emanating from porous MOF-V2O5 NRs-500. Furthermore, the porous MOF-V2O5 NRs-500 skeleton may provide homogenous mass transport channels as well as quick electron transfer.

Ruthenium nanoparticles integrated bimetallic metal-organic framework electrocatalysts for multifunctional electrode materials and practical water electrolysis in seawater.

There is still a significant technical hurdle in the integration of better electrocatalysts with coordinated functional units and morphological integrity that improves reversible electrochemical activity, electrical conductivity, and mass transport capabilities. In this work, ruthenium-integrating porous bimetallic transition metal nanoarrays are efficiently generated from metal-organic framework-covered three-dimensional platforms such as carbon cloth using a simple solution-based deposition technique followed by calcination. Heterostructure ruthenium-cobalt-iron hollow nanoarrays are built to permit exceptionally effective multifunctional activities in reactions including the oxygen evolution reaction, hydrogen evolution reaction, and oxygen reduction reaction. As presumed, the as-synthesized porous nanostructured arrays show remarkable electrochemical performance due to the benefits of copious active reaction sites, and efficient electron and ion transport channels. The oxygen reduction reaction of the porous nanostructured array electrocatalyst has a half-wave potential of 0.875 V vs. reversible hydrogen electrode and can achieve a current density of 10 mA cm-2 at low overpotentials of 220 and 50 mV for the oxygen and hydrogen evolution reactions, respectively, and the needed cell voltage for total water splitting is just 1.49 V at a current density of 10 mA cm-2. The fabricated electrolyzer coupling splits seawater at relatively low cell voltages of 1.54 V at ambient temperature.

Integrating the Essence of a Metal-Organic Framework with Electrospinning: A New Approach for Making a Metal Nanoparticle Confined N-Doped Carbon Nanotubes/Porous Carbon Nanofibrous Membrane for Energy Storage and Conversion.

The fabrication of an economic and efficient multifunctional advanced nanomaterial with a rational composition and configuration by a facile methodology is a crucial challenge. Herein, we are the first to report the growth of Co nanoparticle-integrated nitrogen-doped carbon nanotubes (N-CNTs) on porous carbon nanofibers by simply heating in the situ-developed metal-organic framework (MOF)-based electrospun nanofibrous membrane with no need for an external supply of any additional precursors and reducing gases. The long and entangled N-CNTs originating from highly porous and graphitic carbon nanofibers offer good flexibility, large surface area, high porosity, high conductivity, the homogeneous incorporation of heteroatoms and metallic constituents, and an abundant exposure of active nanocatalytic sites. The as-developed nanoassembly demonstrates attractive characteristics for electrocatalytic hydrogen and oxygen evolution reactions and electrochemical energy storage. This strategy of integrating the essence of an MOF with electrospinning offers a new, direct, and cost-effective approach for making N-doped CNT-based multifunctional membranes.

Fabrication of Nonmetal-Modulated Dual Metal-Organic Platform for Overall Water Splitting and Rechargeable Zinc-Air Batteries.

The fast development of portable water-splitting devices has led to a great deal of work on rechargeable metal-air batteries or solar cells; however, the lack of affordable multifunctional electrocatalysts still hampers their widespread applications. Herein, a well-aligned ternary metal (oxy)hydroxide nanostructure is a sacrificial pseudomorphic transformation template of an integrated metal-organic network on the carbon cloth (CC) surface, that is, the Fe-doped metal-organic framework (MOF) ZnNiCoSe@CC nanosheet network, exhibiting powerful and efficient multifunctional electrocatalysts such as the oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction in alkaline media combined with desirable electrode kinetics. As a proof-of-concept observational study, the nanostructured Fe-doped MOF ZnNiCoSe@CC could be used as air-cathode materials in the rechargeable metal-air battery. The fabricated device delivered higher open-circuit voltage, higher capacity, and peak power density, excellent discharge-charge performance, and long cycle life. Thus, our research creates a unique perspective on the development of highly portable air electrodes with a favorable electrocatalytic application of overall water-splitting reaction.

Vertically Aligned Metal-Organic Framework Derived from Sacrificial Cobalt Nanowire Template Interconnected with Nickel Foam Supported Selenite Network as an Integrated 3D Electrode for Overall Water Splitting.

The development of bifunctional, highly active electrocatalysts for an overall water splitting reaction remains a major challenge. Here, the sacrificial template-assisted transformation of cobalt hydroxide nanowire (Co(OH)2 NW) into a metal-organic framework network (MOF) is conceived as a porous structure that provides extremely active and durable electrochemical energy conversion characteristics. After this, the 1D MOF modified Co NWs can be further transformed into a hybrid structure (MOF CoSeO3 NWs) by selenization. The self-template transformation strategy allows the interconnected porous conductive network to be exposed to abundant reactive sites and to improve electronic conductivity/structural integrity. Thus, the obtained catalyst established by electrocatalytic activity in the course of the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in 1 M KOH solution requires overpotentials (η) of 290 and 150 mV to achieve a current density of 50 and 10 mA cm-2 for both OER and HER. Interestingly, as a full cell water electrolyzer (MOF CoSeO3 NWs (+) // MOF CoSeO3 NWs (-)), the MOF CoSeO3 NW's modified electrode exhibits an affordable cell voltage of 1.675 V at a current density of 100 mA cm-2. This work involves a viable and systematic strategy to prepare many other functional integrated MOFs that can be used for energy storage and conversion in multiple applications.

Phytic acid controlled in situ synthesis of amorphous cobalt phosphate/carbon composite as anode materials with a high mass loading for symmetrical supercapacitor: amorphization of the electrode to boost the energy density.

Transition metal phosphate (TMPi)-based composites as anode electrode materials in supercapacitor applications are less reported. Herein, we report a phytic acid (PA)-assisted in situ-formed amorphous cobalt phosphate/carbon (CoPi/C) composite grown on a flexible woven carbon cloth (CC) via a simple one-step carbonization approach. The tunable synthesis of amorphous and crystalline composites is shown by simply controlling the concentration of the cobalt salts. The strategy for high mass loading to 12 mg cm-2 is also shown in this report. Importantly, the resulting amorphous electrode materials exhibit electric double-layer capacitance (EDLC) behavior that works over a wide potential range from -1.4 to +0.5 V in an aqueous solution of potassium hydroxide (2 M KOH) and from -1.5 to +1.5 V in sodium sulfate (1 M Na2SO4). The amorphous electrode as an anode is capable of delivering an areal capacitance up to 2.15 F cm-2 at a current density of 4 mA cm-2 (gravimetric capacitance up to 606.1 F g-1 at 1 Ag-1) and has a retention of 94.2% at 10 000 cycles. The flexible solid-state symmetric device fabricated shows an energy density of approximately 620.0 µW h cm-2 at a power density of 4.7 mW cm-2 (31.1 W h kg-1 at 476.0 W kg-1). This study offers a novel route for the generation of metal phosphate-based anode materials with high capacitance for symmetrical supercapacitor device with high energy density.

Three-dimensional porous carbonaceous network with in-situ entrapped metallic cobalt for supercapacitor application.

Herein, we outline the fabrication of highly porous three-dimensional carbon-fiber network anchored with uniform metallic cobalt (Co) via electrospinning and subsequent post-modification approaches. First, cobalt acetate solution saturated electrospun polyacrylonitrile (PAN) nanofibrous mat was subjected to sodium borohydride (NaBH4) solution which results in the fabrication of three dimensional (3D) hierarchical multilayer network. Restructuring of the 2D mat into multilayered sponges with metal particles entrapment is attributed to the in-situ generated hydrogen gas into the interconnected pores of the fibrous network simultaneous with reduction of cobalt salt into metallic cobalt by NaBH4. The resulting mesh was stabilized and carbonization at inert atmosphere to obtain metallic cobalt (Co) embedded 3D carbon nanofibrous networks (Co@3D-CNFs). Physicochemical characterization and electrochemical analysis were performed. Results show carbon network was found to be expanded with bubbling like structures often embedded metallic Co nanoparticles. X-ray diffraction (XRD) pattern confirms the existence of the metallic cobalt particles on the carbon fiber networks. Furthermore, we establish a resulting composite (Co@3D-CNFs) identify the enhanced electrochemical performance having specific capacitance 762 F g-1 compared to 173 and 180 F g-1 for corresponding @3D-CNFs and 2D carbon nanofiber network with cobalt doped (Co@2D-CNFs) counterparts, respectively. The assembled Co2@3D-CNFs//NGH ASC device exhibits a high energy density 24.6 W h Kg-1 at 797 W kg-1 power density with an operating voltage of 1.6 V (vs Ag/AgCl). The device further shows good capacitance retention (90.1%) after 5000 cycles. This research shows the simple and cost-effective strategy to make metallic particles embedded 3D porous carbonaceous electrode materials which can have great potential for energy storage application.