Cobalt Metal-organic Framework Research Articles

Textile energy storage: Utilizing binary nickel cobalt metal-organic frameworks and polypyrrole-derived nitrogen-enriched carbons

Textile energy storage: Utilizing binary nickel cobalt metal-organic frameworks and polypyrrole-derived nitrogen-enriched carbons

Operando Electro-Oxidation Reconstitution of a Newly Designed 2D Co(II)-MOF on Nickel Foam to Cobalt Oxyhydroxide Nanosheets towards Energy Sustainability: A Holy Grail in Electrocatalytic Water Splitting.

The upsurging of cost-effective de novo electrocatalysts through the operando electro-oxidation approaches holds great promise for the scalable production of green energy in the pursuit of energy sustainability. This work introduces an operando electro-oxidation reconstitution strategy in producing a smart electrocatalyst, cobalt "oxyhydroxide" derived from a newly designed 2D cobalt(II) metal-organic framework (NBU-4) directly grown on nickel foam (NF), NBU-4/NF@CoOOH. The electrocatalyst, NBU-4/NF@CoOOH, exhibits an outstanding overpotential of 76 mV for the hydrogen evolution reaction and 336 mV for the oxygen evolution reaction to achieve a current density of 10 mA/cm2 with remarkable Faradaic efficiencies of 97.1 and 93.4%, respectively, in 1 M aqueous KOH. Unveiling the bifunctionality of NBU-4/NF@CoOOH as the cathode and anode for overall water splitting in 1 M aqueous KOH, a low voltage of 1.65 V was needed to obtain 10 mA/cm2 current density. Nonetheless, NBU-4/NF@CoOOH displayed excellent stability for 12 h as evidenced from the chronopotentiometry recorded at 10 mA/cm2. The outstanding bifunctional electrocatalytic performance and stability of the electrocatalyst for 50 h is attributed to the unique 2D hexagonal nanosheet morphology of NBU-4/NF@CoOOH and the microporous structure with zigzag flow channels of NF, facilitating a faster kinetics through the Co3+ and Ni2+ dual sites synergism.

Self-standing block shaped cobalt metal organic frameworks deposited graphite rod electrode for non-enzymatic electrochemical detection of imidacloprid in vegetable and fruit

Neonicotinoid pesticides are increasingly being used in agriculture and farming sectors, which can have hostile effects on the environment and water resources. All living creatures including humans had forcefully consumed from the environment this cancerous neonicotinoid pesticide, imidacloprid. Herein, our study reported a novel free-standing electrochemical sensor for ultrasensitive and discriminatory detection of imidacloprid (IM) pesticide using cobalt metal-organic framework (MOF) anchored graphite rod (GR). The surface structure and morphology of the porous Co(pyrazole dicarboxylic acid)[PZDA]MOFs were systematically investigated after solvothermal growth on graphite rods. Electrochemical experiments revealed noteworthy catalytic activity for Co(PZDA)MOF//GR in reducing imidacloprid. The synergistic effect between GRs and Co(PZDA)MOF significantly improves the electrochemical responses. Electrocatalysis studies displayed reversible diffusion-controlled kinetics of four electrons and four protons involved in the electro-reduction of imidacloprid. Detection of IM by differential pulse voltammetry (DPV) method portrays a wide lined dynamic range (0.01 – 100 µM) with a sensitivity of 83.69 μA μM−1 cm−2 and limit of detection value 4.8 nM. Moreover, Co(PZDA)MOF//GR electrode showed an unique electrocatalytic performance and excellent duplicability, outstanding repeatability, and brilliant storing steadiness up to two months. Thus, the sensor electrode provides a simple, affordable, environmentally friendly, cost-effective imidacloprid detection tool in real-world samples.

Electrochemical Sensor Based on Co-MOF for the Detection of Dihydromyricetin in Ampelopsis grossedentata.

Dihydromyricetin (DMY), as the main active ingredient in Ampelopsis grossedentata, is a naturally occurring flavonoid that has attracted extensive attention for its multiple biological activities. For the quick and accurate measurement of DMY, a novel electrochemical sensor based on a glassy carbon electrode (GCE) modified with a cobalt metal-organic framework (Co-MOF) was proposed in this work. The Co-MOF was synthesized via a single-step hydrothermal process using Co(NO3)2·6H2O. Fourier infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy were used to study the morphology and structure of the synthesized Co-MOF. Utilizing differential pulse voltammetry and cyclic voltammetry methods, the effectiveness of DMY electro-oxidation on the Co-MOF/GCE was examined. The results showed that, in comparison to the bare GCE, the electro-oxidation peak current of DMY was considerably increased by the Co-MOF/GCE. The detection limit was 0.07 μM, and the peak current demonstrated two linear relationships in the ranges of 0.2-20 μM and 20-100 μM, with the linear equations of Ip (μA) = 0.4729c (μM) + 1.0822 (R2 = 0.9913) and Ip (μA) = 0.0939c (μM) + 8.4178 (R2 = 0.9971), respectively. The average DMY content in Ampelopsis grossedentata samples was measured to be 3.275 μM, with a good recovery of 108.27% and a relative standard deviation value of 3.46%. The proposed method is simple, rapid and sensitive and can be used for the determination of DMY in Ampelopsis grossedentata.

Design and investigation of a new two-dimensional cobalt metal–organic framework for highly sensitive electrochemical detection of the nitrofurazone drug in food and biological samples

A new two-dimensional cobalt MOF (2D-Co MOF) has been designed and studied to detect nitrofurazone (NFZ), a nitrofuran antibiotic. The MOF sensor demonstrates excellent sensitivity in detecting NFZ, with a remarkably low detection limit of 0.04 μM.

Tailoring the electrochemical performance of rods-like Co-MOF: Fe-derived Co3O4: Fe electrodes for supercapacitor applications

With the increasing global demand for energy, there is a critical need for efficient and sustainable energy storage solutions. Supercapacitors (SCs) have emerged as promising candidates due to their high-power density, long cycle life, and environmental friendliness. This study explores the development of iron-doped cobalt metal–organic frameworks (Co-MOFs: Fe) and their derived oxides supported on Ni foam as high-performance supercapacitor electrodes. The impact of conversion temperature on electrochemical properties of Co-MOFs: Fe derived Co3O4: Fe was evaluated. The results disclosed that the conversion at 500 °C significantly enhances the surface area, specific capacitance, and charge transfer efficiency of the electrodes. It exhibited the highest specific capacity of ∼ 2135.08 F g−1 at a current density of 1 A/g, along with excellent cycling stability of 87 %. Subsequently, an asymmetric supercapacitor was constructed with the MOF-derived Co3O4: Fe at 500 °C as anode and activated carbon as cathode materials. The device exhibited a specific capacitance of 233.98 F g−1 at 1 A/g with an energy density of ∼ 51.99 Wh/kg, power density of 500.14 W/kg, and a significant capacity retention of ∼ 89 % over 10,000 cycles. These findings validate the potential of Co-MOF: Fe derived Fe-doped Co3O4 as potential materials for practical energy storage applications.

Enhanced energy storage efficiency of an innovative three-dimensional nickel cobalt metal organic framework nanocubes with molybdenum disulphide electrode material as a battery-like supercapacitor

Recently, metal-organic frameworks (MOFs) with transition metal sulfides have gained much attention as electrode materials for supercapacitors (SCs). In this work, 3D-NCMOF@MS NCs, incorporating two-dimensional molybdenum disulphide (2D-MS) nanosheets and three-dimensional nickel cobalt-MOF nanocubes (3D-NCMOF NCs) are synthesized by a solvothermal and precipitation process. Owing to their enhanced electrical conductivity and huge surface area, the 3D-NCMOF@MS NCs produce superior electrochemical responses in SCs compared to 2D-MS and 3D-NCMOF NCs. The results demonstrate that the synergistic 3D-NCMOF@MS NCs increased specific capacitance up to 1048 Fg−1 at 1 Ag−1, revealing outstanding cycle stability with a capacitance retention of 99.06 %. Besides, the exposed high-power density of 3D-NCMOF@MS NCs reached 400 W kg−1 as well as an outstanding maximum energy density of 188.64 Wh kg−1. Such synergistic effects of the multivalent states of Ni, Co, and Mo promote electrochemical characteristics, implying that the 3D-NCMOF@MS NCs could potentially be used in energy storage systems, boosting electrochemical performance.

Synthesis, characterization and application of CNTs@Co-MOF and FCNTs@Co-MOF as superior supercapacitor: Experimental and theoretical studies

Supercapacitor offers high power density and quick charge/discharge speed. Herein, a cobalt-metal organic framework (Co-MOF) is synthesized, and the chemical structure is investigated via XRD, FTIR, XPs, and SEM-EDX. Photoluminescence and diffuse reflectance spectroscopy measurements determine the optical properties and band gap. The band gap of Co-MOF is calculated and found to be 1.94 eV, indicating its capability to be applied as a supercapacitor. Carbon nanotubes (CNTs) and functionalized carbon nanotubes (FCNTs) are mixed with Co-MOF to form CNTs@Co-MOFs and FCNTs@Co-MOFs, respectively. The performance of these MOFs as supercapacitors is evaluated using electrochemical measurements. According to the analysis of the super capacitance of the synthesized compounds, FCNTs@Co-MOF shows the highest specific supercapacitance of 454 F g−1, whereas Co-MOF and CNTs@Co-MOF have 263 F g−1 and 338 F g−1, respectively. Besides, the semi-empirical quantum method is used to assess the relationship between the electronic and the experimental data. Experimental and theoretical results recommended the usage of the investigated MOFs as superior supercapacitors.

Adenosine triphosphatase synergetic cobalt metal-organic frameworks with enhanced peroxidase-like activity for L-cystine detection

The role of metal–organic frameworks (MOFs) in the field of enzyme-like materials is significant, and they have been successfully applied to various peroxidase-like studies involving catalytic oxidation of the substrate 3,3′,5,5′-tetramethylbenzidine (TMB). However, the limited chemical stability of MOFs in aqueous environments hampers their catalytic applications. To address this inherent drawback and enhance the peroxidase-like activity of MOFs, a method involving adenosine triphosphate (ATP) bonding was proposed. In this study, collaborative materials comprising cobalt MOFs (Co-MOFs) and ATP were utilized as model catalysts for TMB catalysis. The presence of ATP significantly improved the catalytic capability of Co-MOFs over a pH range from 3 to 9 and temperatures ranging from 25 to 60 °C. Notably, at pH 7 and 60 °C, the catalytic efficiency increased by approximately 100 times and an impressive enhancement rate of up to 4600% was achieved respectively. This peroxidase-like catalytic system offers a colorimetric detection assay that selectively detects L-cysteine with a limit of detection as low as 76.2 nM. Incorporating ATP into Co-MOFs presents a novel approach for utilizing MOFs in catalysis that is convenient, straightforward, and gentle.

Zinc cobaltite embedded in binary metal-organic frameworks using a direct binder-free electrode fabrication approach for efficient energy storage devices and monosodium glutamate detection

There is an imperative need to develop high performance electrode for advance energy storage devices. This work represents the successful synthesis of zinc cobaltite (ZnCo2O4), nickel cobalt metal organic framework, and their composite (ZnCo2O4@NiCo-MOF). The materials are synthesized by using both hydrothermal and sonication techniques. The ZnCo2O4 offers eco-friendly and diffusion regulated properties, while NiCo-MOF provides large specific surface area and tunable pore structure. The ZnCo2O4@NiCo-MOF provide superior electrochemical performance compared to ZnCo2O4 and NiCo-MOF in a three electrode setup. The ZnCo2O4@NiCo-MOF provides a specific capacity of 984 C/g at 1.5 A/g. The ZnCo2O4@NiCo-MOF is also utilized in two electrode setup with activated carbon. The ZnCo2O4@NiCo-MOF//AC device demonstrates the energy density of 92.4 Wh/kg and a power density of 930 W/kg. Additionally, the real time application of ZnCo2O4@NiCo-MOF electrode is also tested in the detection of monosodium glutamate in food. This study highlights the importance of ZnCo2O4@NiCo-MOF electrode materials for future storage and detection devices.

Controlled formation of CoOOH/Co(III)-MOF active phase for boosting electrocatalytic alkaline water oxidation

Surface reconstituted metal-organic frameworks (MOFs) offer appealing properties for electrocatalysis due to their unique structural and compositional advantages. In this work, a controlled potential-induced reconstruction of a two-dimensional cobalt metal-organic framework for boosting oxygen evolution reaction in alkaline media is reported. The current MOF is shown to undergo a partial structural transformation that generates a heterogeneous system, where the original MOF coexists with an oxyhydroxide phase. In fact, the potential-induced stabilization of Co(III) metal centers in the MOF is crucial for delaying its full degradation in alkaline media. This partial retention of the Co(III)MOF phase in the so-derived heterogeneous catalyst has been demonstrated to be decisive for boosting the alkaline electrocatalytic oxygen evolution reaction (OER), displaying superior OER activity in terms of both thermodynamic and kinetic merits compared to the benchmark IrO2 and RuO2 electrocatalysts and the prototypical cobalt (oxy)hydroxides, with a Tafel slope of 52 mV dec−1 and a turnover frequency (TOF) of 6.8 s−1 at 450 mV. Remarkably, the generated final product is stable, exhibiting high robustness and long durability for long-term OER electrolysis. This work provides new insight into the impact of the reconstruction of a MOF for alkaline OER under typical electrochemical conditions, which ultimately benefits the rational design of MOF-based catalysts with high electrocatalytic activity for oxidation reactions.

A nanohybrid-based smartphone-compatible high performance electrochemical glucose sensor

A cost-effective and low-potential smartphone-compatible electrochemical sensor was constructed using a nanohybrid for the sensing of glucose in human and animal serum. The nanohybrid composed of gold nanoparticle (GNP) decorated cobalt hexacyanoferrate (CHCF) modified ZIF-67 (cobalt metal organic framework, CMOF) was synthesized and characterized by FTIR, XRD, and SEM with EDX analysis. The electrochemical characteristics of the nanohybrid were investigated by depositing the nanohybrid over a conventional glassy carbon electrode (GCE) and performing cyclic voltammetry, which revealed a stable redox peak with a formal potential of +0.23 V, corresponding to Co2+/3+ redox couple in GNP–CHCF–CMOF. Thus, developed sensor was utilized for the electrochemical glucose detection, which showed exceptional electrocatalytic activity over a linear detection range from 8.33 to 3793 μM with a low detection limit of 0.96 μM at a low potential of +0.35 V. Furthermore, the GNP–CHCF–CMOF/GCE sensor was employed for the detection of glucose spiked in human and rabbit serum samples, which showed excellent recoveries. A portable measurement device was fabricated which showed the real-time monitoring of glucose in a smartphone. This novel approach paves the way for the design and fabrication of cost-effective, low-potential sensors, which would reduce overall costs and enhance the performance of sensing devices.

Investigations of magnetic and thermal expansion properties of two cobalt(II) metal-organic frameworks constructed by mixed bipyridyl-tetracarboxylate strategy

We report the syntheses, crystal structures, adsorption behavior, thermal expansion behavior, and magnetic properties of two cobalt(II) metal-organic frameworks (MOFs), {[Co(btca)1/2(bpe)(H2O)2]·bpe}n (1) and {Co(btca)1/2(bpe)(DMF)}n (2, H4btca = 1,2,4,5-benzenetetracarboxylic acid; bpe = 1,2-di(4-pyridyl)ethane), constructed using mixed bipyridyl and tetracarboxylate ligands. Single-crystal X-ray diffraction (SC-XRD) indicates that the change of synthetic solvents leads to a significant tuning of structural dimensionality from 2D to 3D framework. Temperature-dependent SC-XRD reveals anisotropically negative and positive thermal expansion of the compounds identified along different crystallographic axes within the frameworks over a 120–400 K temperature range. N2 adsorption measurements indicate a nonporous and ultramicroporous framework for 1 and 2, respectively. Magnetic measurements indicate an easy-plane magnetic anisotropy of the Co2+ ions in the MOFs, with experimental D values of 63.1 and 87.1 cm−1. The ac susceptibility measurements of 1 and 2 show field-induced slow magnetic relaxation below 6 K through different relaxation dynamics. This work not only provides two new cobalt(II) SIM-MOFs, but also presents an effective bipyridyl-tetracarboxylate strategy for designing and building framework materials with interesting magnetic and mechanical properties.

Large ligand metal-organic framework derived CoSe2 to improve sodium storage performance

Cobalt selenide has been regarded as a promising anode for sodium-ion battery owing to its high capacity. However, the issues of stacked problem and volume expansion during cycling significantly affects its performance. Herein, we used large-size ligands to successfully prepared a new cobalt metal–organic frameworks (MOFs), and used as a precursor to prepare CoSe2/MOFc by high-temperature selenization. Morphology characterizations revealed that due to the blocking effect of large-sized ligands, CoSe2 nanoparticles were evenly distributed on the carbon material. As an anode, CoSe2 /MOFc shows a good cyclic stability and high capacity (291 mAhg−1 after 1000 cycles at 1 Ag−1) due to the well dispersion of CoSe2 nanoparticles and the effective coating of carbon matrix. These results indicated that utilizingMOFs precursor with large ligands facilitates the distribution of nanoparticles on conductive carbon, allowing for the synthesis of sodium-ion battery electrodes with superior properties.

Metal-organic frameworks and composites on their basis: structure, synthesis methods, electrochemical properties and application prospects (a review)

Various types of metal-organic frameworks (MOF) and their structural parameters have been reviewed and their classification has been presented. Most widely used synthesis methods and approaches for MOF and composites on their basis have been discussed. MOF structure is a regular 3D lattice formed by organic linkers and metallic clusters. It has been shown for an example of literary data on MOF synthesis and structural studies that the types of bonds and metals can strongly affect the spatial structure and dimensions of MOF crystals: they can have nano-, micro- and meso-dimensions, be dense or porous, bulk or layered. This variety of structural parameters determines the wide range of their properties and potential applications. Prospects and methods of controlling the shapes of the crystals, their size and spatial bonds between organic components and metal ions have been reviewed. Major attention has been paid to zeolite-like frameworks (ZIF) as the most promising ones from the viewpoint of structure, synthesis and electrochemical current source applications. Discussion has touched on possible modifications and methods of controlling the properties of those MOFs and composites on their basis and introduction of impurities, including those having magnetic properties. Possible synthesis options of complex composites through controlled MOF pyrolysis have been presented, for either small-batch or scalable processes. The effect of heat treatment conditions on the final properties and electrochemical applications of those materials has been demonstrated. ZIF-67 structured MOF doping with one more metal has been presented as variant of modifying the properties of MOF and composites on their basis. For example, the Authors have implemented cobalt MOF synthesis wherein cobalt is partially substituted for manganese at the synthesis stage. Furthermore, a simple water solution co-deposition synthesis technique has been modified with ultrasonication thus reducing the time consumption of the process. Electrochemical studies have shown that the unit electrochemical capacity of pyrolyzed MOF electrodes with partial cobalt substitution for manganese is appreciably higher as compared to the manganese-free materials. The unit capacity and energy density increase with manganese content in the MOF. MOF manganese doping delivers a considerable improvement in the electrochemical parameters of the electrode materials for hybrid supercapacitors on their basis (from 100 to 298 F/g at 0.25 A/g current density). The results suggest that cobalt substitution for manganese is an effective method of improving the electrochemical parameters of MOFs. It has been demonstrated that the development of new approaches to the design of MOF based composite materials and the study of the physicochemical regularities of their interaction with various carriers is an important task.

Electrochemical stability and superior capacitance of bismuth cobalt metal-organic framework incorporated with vanadium disulfide nanosheet for supercapacitor application

The development of a novel supercapacitor electrode material consisting of bismuth and cobalt-based metal-organic framework (MOF) intercalated on vanadium disulfide (VS2) nanosheets (BiCo-MOF@VS2). The composite combines the high porosity and tunable functionality of MOFs with excellent conductivity and high theoretical capacitance of VS2. The MOF structure is designed to incorporate bismuth and cobalt, which enhance electrochemical performance. The VS2 nanosheets provide a conductive support matrix for the MOF, facilitating electron transport and promoting fast charge-discharge rates. Researchers used a suite of techniques to characterize the fabricated electrodes to understand the relationship between material properties and performance. These techniques analyzed the morphology, crystal structure, and electrochemical properties of the materials. The electrochemical performance of BiCo-MOF@VS2 electrodes for supercapacitor applications is investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The research shows that these composite electrodes are highly promising for use in supercapacitors needing top performance. They deliver impressive capacitance, handle rapid charge and discharge cycles well, and maintain stability over time. We found that the electrochemical behavior is optimum when BiCo-MOF@VS2 is used, which is a result of the synergistic effects of VS2 dispersion and the BiCo-MOF. BiCo-MOF and VS2 have shown specific capacitance values of 282 and 199 F g−1, compared to the two electrode materials, BiCo-MOF@VS2 demonstrated an impressive specific capacitance of 472 F g−1 at 1 A g−1, and cyclic stability with 85 % retention even after 3000 cycles at 9 A g−1 current density tested in 1 M KOH solution. This novel material holds promise for developing next-generation supercapacitors with exceptional energy storage capabilities.

Exploring the effect of morphology on electrochemical performance of nickel and cobalt metal-organic frameworks and their derivatives for supercapacitor and hydrogen evolution

This study explores the novel approach of investigating the use of binder-free nickel and cobalt metal-organic frameworks and their metal oxide derivatives in 1D, 2D, and 3D morphologies on Ni foam for applications in supercapacitors and hydrogen evolution. This research work involves changing parameters like precursor concentration, organic linkers, and reaction time, leading to the formation of stable one-, two-, and three-dimensional NiO and Co3O4 nanostructures. The morphologies of pristine MOFs and their corresponding oxides were comprehensively verified through FESEM analysis. Significantly, the materials with two-dimensional growth exhibited superior electrochemical performance in supercapacitors and good electrocatalytic performance in hydrogen evolution reaction when compared to their one-dimensional and three-dimensional counterparts. Among them, 2D NiO demonstrated exceptional performance as a supercapacitor electrode, with a specific capacity of 688.13 C g−1 (1376.26 F g−1) at 1 A g−1, surpassing 1D and 3D NiO nanostructures. It also demonstrated good stability by retaining 93.1 % of its initial capacity after 5000 cycles at 10 A g−1. The assembled asymmetric supercapacitor (ASC) achieved a high energy density of 65.27 Wh kg−1 at 375 W kg−1, maintaining 33.18 Wh kg−1 even at 7500 W kg−1. It also maintained 87.8 % retention of its initial capacity up to 5000 cycles at 10 A g−1. Furthermore, when tested for HER, all oxides exhibited better performances with specifically 2D NiO exhibiting good catalytic performance, reaching 10 mA cm−2 at a low overpotential of 129 mV (vs. RHE) and displaying remarkable stability over 24 h. This study upholds the superiority of two-dimensional sheet-like structures with interconnected network of nanoparticles in electrochemical and electrocatalytic performance compared to one-dimensional rod-like and three-dimensional pyramid-like structures.

Highly efficient activation of peroxymonosulfate by MOF derived CoS2@C for degradation of ciprofloxacin

The cobalt disulfide/carbon composite CoS2@C was successfully synthesized using cobalt metal–organic frameworks (MOFs) with different ligands as templates by pyrolysis method. The as-prepared CoS2@C were applied as catalysts of peroxymonosulfate (PMS) for the degradation of antibiotics. The CoS2@C-3, which was prepared using Co-MOF-74 as self-template, exhibited extraordinarily high activity to PMS, more than 90 % of ciprofloxacin (CIP) was degraded in 10 min with a rate constant of 0.249 min−1. Furthermore, the CoS2@C-3/PMS system demonstrated exceptional resistance to humic acid (HA), significant environmental stability, and a wide range of pH adaptation. The SO4•−, ·OH, and 1O2 induced from heterogeneous and homogeneous activation of PMS were identified as reactive oxygen specieses (ROSs) responsible for oxidation of CIP. In addition, electron transfer and Co(IV) = O also participated in the CIP degradation process. According to the results, a plausible catalytic mechanism for PMS by CoS2@C was elucidated, in which S is crucial to the regeneration of ≡Co(II) in situ. Four potential degradation pathways were proposed after the CIP intermediate products were analysed by HPLC-MS. The findings of this study might offer us some insight into how metal sulfides made from MOFs can be effectively used to eliminate contaminants by activating PMS.

A novel hierarchic hydrothermal strategy to enhance the performance of nickel-cobalt metal-organic framework for supercapacitors

The study presents a novel hierarchical hydrothermal strategy, which can not only ensure the morphology characteristics of the initial hydrothermal products, but also enhance the properties of the materials. Here, the hierarchical hydrothermal treatment was carried out with bimetallic nickel cobalt metal organic framework (NiCo-MOF) as the representative. The results of characterization and electrochemical tests showed that NiCo-MOF after hierarchical hydrothermal treatment (NCM-H) not only exhibits enhanced stability in crystal morphology but also an increased number of active sites in the material. At the same time, compared with the initial hydrothermal NiCo-MOF (NCM-F), the rate performance and cycle stability of NCM-H have been greatly improved. The prepared NCM-H electrode demonstrates a remarkable specific capacity of 1006F g−1 at 1 A/g. Furthermore, the assembled NCM-H//AC asymmetric supercapacitor (ASC) device demonstrates a remarkable energy density of 100.8 Wh kg−1 at a power density of 750 W kg−1. Excellent rate performance (76.4 % retention from 1 A/g to 20 A/g) and cycling stability (83.8 % after 5000 cycles). This unique hierarchical hydrothermal strategy is convenient, efficient, environmentally friendly and low-cost, and can provide a meaningful reference for the performance improvement of MOF-based and other related materials.

Molybdenum nitride thin films coated cobalt-metal-organic framework nanocolumns for high-efficiency alkaline hydrogen evolution

The sustainable development of catalysts with Pt-like catalytic activity to produce hydrogen economically from water electrolysis is essential and challenging. Herein, we have prepared a novel catalyst with the combined virtues of nanocolumn structures and heterojunctions by magnetron sputtering molybdenum nitride (Mo2N) thin films over cobalt-metal-organic framework (Co-MOF) nanocolumns on carbon paper (CP), and explored the catalytic activities in hydrogen evolution reaction (HER). By optimizing the preparation process, the heterostructured Co-MOF@Mo2N/CP catalysts can exhibit an excellent HER performance with an overpotential of only 72.8 mV at 10 mA cm−2 and cycling durability over 24 h and 5000 cycles, achieving one of the best performances among state-of-the-art Mo-based catalysts. This work guides and accelerates the design of low-cost and high-performance transition metal nitrides HER catalysts for industrial applications.