A novel moss-like 3D Ni-MOF for high performance supercapacitor electrode material

Kg-Scale Synthesis of Ultrathin Single-Crystalline MOF/GO/MOF Sandwich Nanosheets with Elevated Electrochemical Performance

The scalable preparation of 2D ultrathin metal-organic framework (MOF) nanosheets remains a significant challenge due to low stripping efficiency and susceptibility to agglomeration. Herein, a facile strategy is developed for the synthesis of 2D ultrathin single-crystal MOF/graphene oxide (GO)/MOF (MGM) sandwich-like nanosheets based on the Ni/Co-BDC MOF (BDC = 1,4-terephthalic acid), with GO serving as a structure-directing agent. Impressively, 1 kg of MGM nanosheets can be obtained in a single batch with a metal-based yield of 98.73%. Furthermore, the universality of this strategy is implemented by the successful synthesis of three additional 2D ultrathin nanosheets: MGM7-ABDC, MGM7-FBDC, and MGM7-BPDC (metal = Ni, Co; ligands = 2-aminoterephthalic acid (2-ABDC), 2-fluoroterephthalic acid (2-FBDC), and 4,4'- biphenyl dicarboxylic acid (BPDC)). The as-prepared MGM7 nanosheets (Ni: Co ratio = 7:3) exhibit excellent electrochemical performance as the cathode for aqueous basic zinc battery (159.2 mA h g-1 at 1 A g-1), anode for sodium-ion battery (SIB, 593.0 mA h g-1 at 0.2 A g-1), and electrocatalyst for the oxygen evolution reaction (OER, 224 mV overpotential at 10 mA cm-2), significantly outperforming both bulk MOFs and conventional MOF nanosheets. This work enables the scalable synthesis of 2D MOF nanosheets with enhanced properties for multiple applications.

Facile Growing of Ni-MOFs on Ni Foam by Self-Dissociation Strategy for Electrochemical Energy Storage

Metal-organic frameworks (MOFs) with redox metal centers have come into view as potential materials for electrochemical energy storage. However, the poor electrical conductivity largely impedes the potentiality of MOFs to construct high-performance electrodes in supercapacitors. In this work, a self-dissociation strategy has been applied to construct Ni-MOF microbelts on Ni foam (NF), where the NF is used as both a support and a Ni source. The transmission channels between the Ni-MOF and NF are favorable for the charge transport due to the in situ self-assembly of the TPA linkers with the dissociated Ni ions from the Ni foam. The grown Ni-MOF microbelt arrays can offer abundant active sites for redox reactions. The prepared Ni-MOF/NF-s electrode can yield a high capacitance of 1124 F g-1 at 1 A g-1 and retains 590 F g-1 at 10 A g-1. This design may offer a controllable protocol for the construction of MOF microbelt arrays on various metal substrates.

In situ growth of binder-free CoNi0.5-MOF/CC electrode for high-performance flexible solid-state supercapacitor application

Metal organic frameworks (MOFs) with binder-free electrodes have shown promise for portable electrochemical energy storage applications. However, their low specific capacitance and challenges associated with the attachment of active materials to the substrate constrain their practical utility. In this research, we prepared a CoNi0.5-MOF/CC electrode by in situ growth of CoNi0.5-MOF on an H2O2-pretreated carbon cloth (CC) without using any binder. It exhibits a higher specific capacitance of 1337.5 F g-1 than that of CoNi0.5-MOF (∼578 F g-1) at a current density of 1 A g-1 and an excellent rate ability of 88% specific capacitance retention at a current density of 10 A g-1 after 6000 cycles. The as-assembled flexible asymmetric solid-state supercapacitor based on the CoNi0.5-MOF/CC positive electrode and a nitrogen-doped graphene (N-Gr) negative electrode exhibits an energy density of 61.46 W h kg-1 at a power density of 1244.56 W kg-1 and holds a stable capacitance of ∼125 F g-1 at 1 A g-1 when the flexible supercapacitor is bent, showing great potential for flexible electronics application. The H2O2 is indicated to play an important role, enhancing the adhesion of CoNi0.5-MOF on CC and reducing its charge transfer resistance by functionalizing the carbon fiber during the pretreatment of the CC matrix. The results provide a great way to prepare a flexible asymmetric solid-state supercapacitor with both high power density and high energy density for practical application.

M-Ni-Co MOF (M=Zn, Fe, Mn) for high-performance supercapacitors by adjusting its morphology

Metal-organic frameworks (MOF) have been wildly synthesised and studied as electrode materials for supercapacitors, and bimetallic MOF of Ni and Co has been broadly studied to enhance both specific capacitance and stability of supercapacitors. Herein, a best performance (about 320 F/g) of Ni-Co bimetallic MOF was found in a uniform preparation condition by adjusting the ratio of Ni to Co. Then tiny third metal ion was introduced, and we found that the morphology of material has a significant change on the original basis. Furthermore, certain ions (Zn, Fe, Mn) introduced make a huge improvement in capacitance based on Ni-Co MOF of 320 F/g. The result shows that Zn-Ni-Co MOF, Fe-Ni-Co MOF and Mn-Ni-Co MOF perform specific capacitance of 1135 F/g, 870 F/g and 760F/g at 1 A/g, respectively. Meanwhile, the asymmetric supercapacitor (ASC) was constructed by Zn-Ni-Co MOF as positive electrode and active carbon (AC) as negative electrode. The Zn-Ni-Co MOF//AC ASC possesses a energy density of 58 Wh/kg at a power density of 775 W/kg. This research provides a new methods to regulate the morphology of MOF and a novel viewpoint for assembling high-performance, low-price, and eco-friendly green energy storage devices.

Effect of Solvothermal Temperature on Morphology and Supercapacitor Performance of Ni-MOF

A series of Ni-MOF materials were synthesized via a simple hydrothermal method and can be employed as electrodes for supercapacitors (SCs). Different temperatures were selected to unveil the effect of temperature on the formation, structure, and electrochemical performance of Ni-MOF-x (x = 60, 80, 100, and 120). Ni-MOF-80 possessed a larger specific surface area with a cross-network structure formed on its surface. The synthesized Ni-MOF electrode delivered a specific capacity of 30.89 mA h g^-1 when the current density reached 1 A g^-1 in a three-electrode system. The as-fabricated Ni-MOF materials could be further designed and are expected to deliver satisfactory performance in practice.