Preparation And Electrochemical Performance Of Supported Cobalt-based Catalysts

In the context of increasing energy consumption,environmental problems are becoming more and more serious.It is very important to find clean renewable energy to replace fossil fuels.Hydrogen is considered as an ideal clean energy because of its high energy density and the only by-product when it is burned is water.Electrocatalytic water decomposition of alkaline medium is one of the effective ways to obtain hydrogen energy,but the slow kinetics of electrolytic water cathode and anode seriously hinder efficient and sustainable hydrogen production.Precious metal（Pt/Ir）based catalysts are excellent electrocatalysts,but their rarity and high cost limit their large-scale use.Therefore,efficient and cheap electrocatalysts are needed to replace them.Transition metals have high intrinsic catalytic activity and are suitable for cathode and anode electrocatalysts.In this paper,Co-Mo-Fe/NF and Co-Mo-Ni Fe₂O₄/NF catalysts were prepared based on cobalt-molybdenum catalyst from two different perspectives of doping and construction of heterogeneous interfaces,and the composition,structure and electrochemical performance of the catalysts were systematically studied.Specific research contents are as follows:1.The Co-Mo/NF catalyst was prepared on the foam nickel substrate by electrodeposition method,and then the amorphous Co-Mo-Fe/NF catalyst was obtained by Fe-doped co-electrodeposition.Scanning electron microscopy（SEM）was used to characterize the surface morphology of the catalyst,and it was known that the surface morphology of the catalyst presented a small particle structure,which provided a larger specific surface area and more reaction sites for the electrochemical reaction.Transmission electron microscopy（TEM）was used to observe that the catalyst was a long-range disordered short-range ordered amorphous structure.The coordination defects in the structure provided more active reaction sites for the reaction and accelerated the catalytic reaction kinetics.The amorphous structure of the catalyst was confirmed by X-ray diffraction（XRD）patterns with broad diffraction peaks.The chemical states of Co-Mo/NF and Co-Mo-Fe/NF catalysts before and after the reaction were characterized by X-ray photoelectron spectroscopy（XPS）.It was found that Co-Mo-Fe/NF had electronic interaction and reactive substances,indicating the synergistic effect between Co,Mo and Fe.According to the results of electrochemical test,the OER overpotential of Co-Mo-Fe/NF in alkaline medium is218 m V,which can stimulate the current density of 10 m A cm^-2,and has a low tafel slope(45 m V dec^-1)and good electrochemical stability（continuous stable working for24 h）.2.One the basis of Co-Mo/NF catalyst,the heterogeneous interface was constructed by adding Ni Fe₂O₄ nanoparticles.The Co-Mo-Ni Fe₂O₄/NF composite catalyst was prepared by co-electrodeposition.XRD and TEM characterization showed that the catalyst formed a composite structure of amorphous and microcrystalline.The change of binding energy of elements on the catalyst surface was characterized by XPS,and it was found that there was a large change of binding energy of elements,indicating that electron transfer occurred between Ni Fe₂O₄,Co and Mo.In short,the heterogeneous interface established by Ni Fe₂O₄,Co and Mo and the synergistic effect between the two enhance the charge transfer and further improve the catalyst activity.The electrochemical test found that HER overpotential was 13m V and the tafel slope was 70.86 m V dec^-1 when the current density of 10 m A cm^-2was driven in alkaline medium,and it could also stabilize the catalysis for 24 h.Co-Mo-Fe/NF and Co-Mo-Ni Fe₂O₄/NF catalysts were prepared by the above different design strategies.It provides insight for preparation of good OER and HER performance catalysts.