Design And Synthesis Of MOF Derived Iron Metal-based Electrode Materials And Regulation Of Electrocatalytic Performance

In today’s world,environmental pollution and energy shortages are becoming increasingly severe,and there is an urgent need to develop efficient and stable new energy sources,as well as energy conversion and storage devices to replace traditional fossil fuels.Electrolytic water equipment and zinc air battery have become the representative equipment for the storage and conversion of renewable energy such as wind energy,solar energy,tidal energy and so on.They have broad application prospects and become the research focus of researchers.Due to the slow kinetics and high overpotential of hydrogen evolution reaction（HER）,oxygen evolution reaction（OER）,and oxygen reduction reaction（ORR）,their large-scale application is limited.Therefore,it is extremely urgent to develop low-cost,efficient,and stable electrocatalysts.Metal organic framework（MOF）is a periodic porous material formed by connecting organic ligands with metal ions/clusters.Due to its controllable composition,rich porous structure and high specific surface area,it can be further transformed into the corresponding MOF derived metal/carbon hybrid material through high-temperature pyrolysis.Thanks to the synergetic catalysis between various components,it is possible to regulate the electronic structure of electrocatalysis and optimize the adsorption/desorption energy barrier of reaction intermediates in the catalytic process.The main research contents are as follows:（1）Using ZIF-8-Zn/Ni nanocubes as precursors and utilizing the targeted transport function of polydopamine,metal Fe and Ni were introduced onto the outer surface of ZIF-8-Zn/Ni nanocubes;After high-temperature pyrolysis treatment,a nitrogen-doped carbon skeleton embedded with Fe-Ni alloy ions was successfully constructed.The electrocatalytic experiment showed that the obtained electrocatalyst exhibited excellent ORR-OER activity;In alkaline electrolyte,the half-wave potential is as high as 0.891 V.At a current density of 10 m A/cm²,the overpotential of OER is 325 m V,which is superior to commercial Pt/C and Ru O₂;In addition,based on Fe-Ni@NDC The zinc-air battery made of materials has a high specific capacity(773 m Ah/g _Zn),excellent power density（270 m W/cm²）,and stability for up to 130 hours.Compared with precious metal based zinc-air batteries,it exhibits superior discharge performance and cycle stability.Theoretical simulation shows that the alloying of Ni and Fe can well manipulate the electronic structure,lead to good charge transfer between metals,and thus reduce the d-band center of the Fe adsorption site,which is helpful to significantly reduce the reaction barriers of intermediates involved in the electrocatalytic ORR/OER process.（2）Using ZIF-8-Zn/Fe as the precursor,Mo is uniformly loaded onto the surface of ZIF-8-Zn/Fe using dopamine targeting,forming ZIF-8-Zn/Fe@PDA-Mo;Finally,wrap ZIF-8-Zn/Fe/Ni again outside dopamine.During high-temperature treatment,organic ligands can reduce Fe and nickel metal ions to metallic states,thereby forming alloy structures;Mo components can form Mo₂C with carbon and couple with Fe-Ni alloys.Thanks to the synergistic catalytic effect between multiple components,the obtained Fe Ni/Mo₂C@NDC material exhibits excellent reversible oxygen electrocatalytic activity,with an ORR half wave potential of 0.91 V and an OER overpotential of 290 m V at a current density of 10 m A/cm².In addition,the assembled zinc air battery exhibits high specific capacity(794 m Ah/g _Zn)and excellent cycling stability（195 h）.（3）The metal organic framework（MOF-74）supported on foam nickel（NF）substrate was used as the precursor to convert it into cobalt doped Ni（OH）₂ nanosheets by alkali etching technology.Thanks to Co-Ni（OH）₂@NF The electrode has excellent charge transfer ability and matched electrochemical window,achieving two-step electrolysis of water for hydrogen and oxygen production under membrane free conditions.Specifically,at a current of 100 m A,the first HER process on the cathode can be maintained for 1300 seconds,while the corresponding Ni（OH）₂ charge medium is simultaneously oxidized to Ni OOH,and the battery voltage is 1.542 V.The subsequent OER process includes reduction/regeneration of Ni（OH）₂ buffer electrodes（from Ni OOH to Ni（OH）₂）and O₂ precipitation from the anode,with a voltage of 0.291 V.In addition,by combining Ni OOH and zinc sheets,a Ni Zn battery was further assembled,where the discharge process of the battery can replace the OER process in the second step and achieve the reduction of the buffer medium.The coupling of electrochemical hydrogen evolution and Ni-Zn battery discharge process can provide a new approach for hydrogen production by electrolysis of water without external power supply.Experiments and theoretical calculations show that cobalt doping not only improves the conductivity of the electrode,but also changes the cathodic oxidation and reduction potential of the electrode,and improves the adsorption and affinity of the buffer medium for OH ions,thus promoting the improvement of HER and OER activities.Figure[67]Table[9]Reference[140]...