Design And Energy Storage Mechanism Study Of Co-Based MOFs And Their Derived Composite Materials Structures

Actively promoting the development of renewable energy is an effective strategy to reduce dependence on fossil fuels.However,new types of renewable energy such as wind energy,geothermal energy,and tidal energy are limited by natural factors such as geography and climate.Additionally,they face challenges of storage difficulty and intermittent supply,making it complex to balance fluctuating load demands and energy supply.In order to more effectively utilize renewable energy,advanced energy storage devices need to be developed to improve the controllability and availability of energy.In this context,novel porous crystalline materials such as metal-organic frameworks have attracted considerable attention.Due to their unique properties,Co-based MOFs（such as ZIF-67,Co-based MOFs-71,and Co-based MOFs-74）have aroused widespread interest among researchers in the field of energy storage and conversion.Their advantages include high surface area,tunable pore structures,diverse chemical compositions,convenient synthesis,and controllable physicochemical properties.Based on these characteristics,Co-based MOFs and their derivative composite materials have been widely applied in various emerging energy storage systems,such as serving as anode materials for alkaline metal ion batteries to address ion transport and storage issues,acting as protective layers in zinc aqueous ion batteries to enhance anode stability,or functioning as efficient dual-function catalysts in air batteries.However,as of now,the mechanisms of action of Co-based MOFs and their derivative materials in these energy storage systems have not been fully elucidated,limiting researchers’ability to further optimize the energy storage performance of these systems.To address these issues,this paper starts from the structural design of Co-based MOFs and their derivative materials.Through methods such as heterostructure assembly and composite formation with two-dimensional materials,high-performance nanomaterials suitable for different electrochemical energy storage fields were synthesized,and their energy storage mechanisms were deeply explored.The paper systematically studies the high-value applications of Co-based MOFs in the field of energy storage,with the main research contents as follows:[provide a brief summary of the main research contents here:（1）Co/CoSe ultrafine nano-crystal heterojunction hollow carbon nanospheres derived from MOFs were prepared through a hydrothermal method as negative electrode materials for potassium-ion batterie.The internal hollow structure of carbon nanospheres effectively reduces the overall mass of the negative electrode while significantly enhancing the specific surface area.The surface crystal heterojunction structure effectively improves the distribution of electronic clouds in the material.The prepared negative electrode material exhibits stable capacity at 461.9 mAh g^-1 after 200 cycles at a current density of 1 A g^-1.Under a current density of 10 A g^-1,the capacity remains at 145.9 mAh g^-1 after 3000 cycles,indicating the sufficient structural stability of the negative electrode material for prolonged potassium-ion storage tasks.（2）WSe₂/ZIF composite materials based on ZIF-67 were successfully synthesized and employed as an artificial interface protective layer for Zn negative electrodes through a simple spin-coating method.The amorphous WSe₂ increases active sites,ensuring a uniform Zn²⁺flux.The protective layer,with a high specific surface area,also enhances electrolyte improving reaction kinetics.WSe₂/ZIF significantly enhances reversible stripping and plating reactions in symmetrical batteries,achieving over 700 and 1000 hours of cycling at current densities of 1 and 5 mA cm^-2,respectively.Various characterization results indicate that the artificial WSe₂/ZIF interface possesses enhanced diffusion kinetics and robust mechanical integrity.Furthermore,full-cell testing of WSe₂/ZIF confirms the outstanding performance of the WSe₂/ZIF negative electrode,maintaining a discharge specific capacity of 93.4 mAh g^-1after 200 cycles.（3）Synthesized bimetallic Co-based MOFs/MXene composite ORR catalyst and applied it to efficient zinc-air battery anode.ZIF-67 was used as the MOFs matrix,with Fe,Ni,Cu,Mn as the second-phase metal ligands for preparing Co-based bimetallic MOFs.MXene was electrostatically attracted and combined with Co-based bimetallic MOFs,followed by rapid annealing at high temperatures to create a dual-function catalyst with a protective MXene layer.The resulting Co/M_H-N-C exhibited a high surface area,3.5-3.7 nm pore size,and internal metal cluster sizes between 5-10 nm.Electrochemical test results demonstrated excellent catalytic performance and structural stability of Co/M_H-N-C under both acidic and alkaline conditions.The optimized Co/Ni H-N-C exhibited an overpotential of only 405 mV at a current density of 20 mA cm^-2,with a Tafel slope of 62 mV dec^-1,surpassing many precious metal catalysts.The zinc-air battery anode prepared with Co/Ni _H-N-C maintained stable cycling for over 400 hours at a current density of 10 mA cm^-2,achieving a peak power density of 241.7 mW cm^-2.These findings indicate promising applications of Co-based MOFs composite materials in the field of energy storage.