Studies On Preparation And Performance Of Transition Metal Organic Frameworks And Their Derived Electrocatalysts For Oxygen Reaction

Oxygen reduction reaction（ORR）is an important cathode reaction in metal air battery,fuel cells and other renewable electrochemical energy storage systems.It is of great significance to explore cost-effective and high-performance non-noble metal based electrocatalysts for ORR.As a new energy with zero pollution,hydrogen energy is considered as an energy carrier to replace fossil fuel energy.The slow oxygen evolution reaction（OER）in overall water splitting for hydrogen production greatly hindered the efficient of overall water splitting.In order to realize the wide application of overall water splitting,it is necessary to develop low cost,high performance and high stability of non-noble metal based OER electrocatalysts.Metal-organic frameworks（MOFs）derivatives have been widely used in electrocatalysis in recent years due to their structural adjustability,large surface area and abundant pore size.In this paper,the pincer nitrogenated ligand H₂L(1,3-（bis（6-（2-methyl）nicotinyl）pyridine）was used to react with the transition metal salt to synthesize MOF materials（and further carbonize）and prepare catalysts with different electrochemical properties.（1）A Zn/Fe-MOF-derived Fe₃C coupling Fe N_xcatalyst constructed via coordination confinement pyrolysis effect successfully.The optimized catalyst Fe₃C-Fe N_x/NC-7 demonstrates superior ORR activity in 0.1 M KOH,the half-wave potential(E_1/2)reaches up to 0.93 V with the limiting current density（j _L）of 5.65m A/cm²at 5 m V/s scanning rate and 1600 rpm.The assembled primary zinc-air battery（ZAB）displays a satisfying open-circuit potential（OCV）of 1.53 V and an excellent specific capacity of 835 m A·h·g^-1,the peak power density achieves 283m W/cm²,outclassing the commercial Pt/C-based ZAB.This result further demonstrates the promising application prospect of the catalyst cooperated metallic nanoparticle（NPs）with isolated single metal species.（2）In this study,the ultra-stable Co-Co₇Fe₃heterostructure coupled with nitrogen-doped carbon（NC）material was prepared by coordination constrained pyrolysis strategy,which improves the conductivity,accelerates the reaction kinetics,and optimizes the adsorption energy of ORR/OER intermediates.The optimized Co-Co₇Fe₃@NC-M catalyst exhibits remarkable bifunctional activity with the E_1/2of0.881 V in 0.1 M KOH for ORR,and the overpotential of 292 m V at 10 m A/cm²(E_j=10)in 1 M KOH for OER.Moreover,the tiny potential gapΔE(ΔE=E_j=10-E_1/2)of 0.641 V was obtained between the potentials,outperforming most reported bifunctional electrocatalysts and the commercial combination of Pt/C-Ru O₂.The primary ZAB assembled with Co-Co₇Fe₃@NC-M as cathode displays a superior 1.50 V open-circuit potential,a large specific capacity of 878 m A·h·g^-1,and a high peak power density of334 m W/cm².Furthermore,the rechargeable ZAB reveals long-term cyclability,offering a 1.19 V discharge voltage and a 1.77 V recharge voltage over 160 h（ΔE=0.58V）.This result demonstrates the application potential of multi-metallic NPs coupling N-doped carbon matrix in energy conversion.（3）Using nickel foam（NF）as the nickel source and conductive substrate,MOF and hydroxide coexisting heterostructures Ni-MOF@LDH/NF were prepared with a small amount of ligands and no additional metal salts.Electrocatalysts Ni Fe-MOF@LDH/NF with high OER performance were prepared by further Fe doping.When the current density（j）is 10,50 and 100 m A/cm²,the overpotential is228 m V,256 m V and 272 m V,respectively.And the voltage of overall water splitting is as low as 1.66 V,and the OER working potential required to maintain 10 m A/cm²in24 h is only slightly increased by 2.0%.Figure 49 Table 4 Reference 117...