Construction And Electrochemical Oxygen Evolution Performance Of Transition Metal MOF-based Nanomaterials

Serious environmental pollution caused by fossil fuel consumption and urgent energy demand caused by human social development have forced mankind to develop green and renewable energy sources those can replace fossil fuels.Among the various renewable energy sources,hydrogen energy has received significant attention according to its own unique advantages.While the electrocatalytic water splitting technology is considered as one of the best choices among practical hydrogen production methods in industry due to the regenerable and non-polluting process,which generally uses noble metal-based electrocatalysts to overcome the activation energy barrier in the production process.Nevertheless,noble metal-based electrocatalysts are expensive and scarce in reserves,therefore,the development of efficient and stable non-noble metal-based electrocatalysts to replace noble metal-based electrocatalysts is urgently demanded.Metal organic frameworks（MOFs）have gained recognition and attention from researchers in the field of electrocatalysts because of their large specific surface area,high porosity,high dispersion of metal active sites,flexible structure,diverse topology and facile functionalization.In this article,self-supported MOFs-derived material electrocatalysts Ir-Co（OH）₂@ZIF-67/NF and NiCoFe-LTH@NiCo-MOF/NF were prepared on conducting substrates by room-temperature immersion or solvothermal methods using heteroatom doping and in situ hydrolytic transformation strategies,and the link between the composition structure and catalytic performance of the electrocatalysts was investigated in depth.The contents are as follows:（1）Firstly,ZIF-67 was grown on NF using a simple one-step room temperature soaking method,and subsequently,a one-step solvothermal method was utilized to achieve in situ hydrolytic conversion,Ir doping,finally,Ir-doped Co（OH）₂nano electrocatalyst was prepared on bare nickel foam substrate.Thanks to the combination of MOFs with highly conductive nickel foam substrates,the unique multilayer nanosheet structure and the doping of Ir that activates the active sites of Co ions and modifies the electronic structure of Co ions,the Ir-Co（OH）₂@ZIF-67/NF material exhibits excellent OER performance and favorable stability,which only requires ultra-low overpotentials of 198,263,300 mV to achieve current densities of 10,50,100 mA cm^-2,and it can operate stably for at least 16 h.The various strategies of this research work can be generalized to other MOFs-derived materials to offer innovative thoughts and schemes for the development of electrocatalysts for massive hydrogen production in practical industries.（2）Firstly,NiCo-MOF was grown on NF using a simple one-step solvothermal method,and subsequently,a one-step solvothermal method was utilized to achieve the in situ hydrolytic conversion.Fe doping again,finally,NiCoFe layered ternary hydroxide（NiCoFe LTH）was prepared on bare nickel foam substrate.Thanks to the combination of MOFs with highly conductive nickel foam substrates,the unique flower-like nanosheet microsphere structure,the synergistic effect existing between Ni,Co,Fe tri-metals and the synergistic effect existing between OER active phases Ni OOH/Co OOH/CoO₂/Fe（OH）₃/NiCoFe-LTH,NiCoFe-LTH@NiCo-MOF/NF material exhibits excellent OER performance and favorable stability,which only requires ultra-low overpotentials of 207 and 283 mV to achieve current densities of 10 and 100 mA cm^-2,and it can operate stably for at least 16 h.The performance of such material is similar to that of noble metal-based electrocatalysts used for commercial hydrogen production,and the research ideas and strategies in this work can provide valuable references for future researchers to prepare more superior MOF-based electrocatalysts.