Synthesis Of Bimetallic Framework Materials And Study Of Oxygen Evolution Reaction Properties

Because fossil fuels are non-renewable,and the greenhouse gases emitted have adverse effects on the environment.Hydrogen energy,as one of the green energy sources,has the advantages of high abundance,renewable,high combustion value,clean,and pollution-free products.Electrochemical decomposition of water to produce hydrogen has a faster rate and no excess by-products.Ir O₂ and Ru O₂ are the most commonly used anode catalysts.However,precious metal catalysts are expensive.Therefore,the effective use of the rich non-noble metal electrocatalysts on the earth as different combinations of nanostructures in the decomposition of water is the core of replacing precious metals for hydrogen production industrialization.Metal-Organic Framework（MOF）materials have attracted wide interest due to their unique porous structure,the advantages of composition,and structure orientable design.Composites can usually be obtained by post-treatment.The introduction of bimetallic centers or trimetallic species in MOFs materials is beneficial to improve the associated electrocatalytic performance,since the hybridization of different metal centers can provide synergistic effects.But most bimetallic catalysts are prepared under high temperature and high pressure or extreme conditions.Taking into account the above problems,the development of energy saving,high efficiency and environmental protection system,the effective preparation of composite metal MOFs materials as OER electrocatalysts,and the detailed discussion of its catalytic mechanism and structure-activity relationship have become the key to solve the development problems in this field.Therefore,this research is devoted to the selection of bimetallic MOFs materials under mild conditions,and effective post-modification for oxygen evolution reaction（OER）under alkaline conditions.The main results are as follows:（1）A simple and controllable synthesis strategy for OER bimetallic electrocatalysts based on two-dimensional（2D）Fe-based metal-organic frameworks（HUST-8,HUST=Hua zhong University of Science and Technology）was explored.An unoccupied porphyrin center is placed in a HUST-8 layer structure.This is very convenient for introducing the second kind of metal center through post-modification treatment.Guided by the synthesis strategy,Fe/Ni,Fe/Co,Fe/Zn,Fe/Mn,and Fe/Fe substances ware prepared.Among them,Fe/Ni sample showed the best catalytic activity.In 1 M KOH,the OER activity showed an initial potential of 170 m V（relative to RHE）at 10 m A cm^-2,corresponding overpotential240 m V.Tafel slope is 60.8 m V dec^-1.All these experimental results of the Ni@HUST-8are better than commercial Ir O₂.Compared to other bimetallic species,Ni@HUST-8,with higher electrocatalytic performance,should be attributed to the special synergy between Fe and Ni centers,and tend to greatly improve reaction kinetics and charge transfer efficiency.At the same time,this study clearly demonstrates the important role of bimetallic centers in the synergistic effect of OER,and explores other possibilities for preparing derived electrocatalysts based on MOF templates.（2）We explored a CoNi-based organic framework material synthesized under mild conditions and used it as a template material to obtain disordered porous nanosheet after Na BH₄ post-treatment.The effects of different doping ratios and different modification times on the electrocatalytic performance of OER were investigated by series characterization,in which Co_0.9Ni_0.1MOF-10min,showed the best catalytic activity.When the current density is 10 m A cm^-2,the overpotential is 0.264 V,the tafel slope is 56.2 m V dec^-1,and the stability is strong.These experimental results show that the performance of Co_0.9Ni_0.1MOF-10min is better than that Ir O₂.Compared with single metal Co MOF and other samples with different modification times,Co_0.9Ni_0.1MOF-10min samples produced high valence Co and Ni porous nanosheet structures and numerous defects,which effectively increases the exposure area of the material active sites,Ni²⁺and Co²⁺transfer electrons through coordinated O atoms,which creates a strong synergy.B atoms entered into the frame,effectively changing Co Ni orbital levels,significantly improving reaction kinetics and charge transfer efficiency,which is the corresponding OER performance.This study shows the importance of bimetallic center synergy and effective post-modification to improve OER performance,and provides MOFs research ideas for derivative materials as electrocatalysts.