Ni₃S₂ Nanorod@Ni-Fe Layered Double Hydroxide Nanofilm With Excellent Electrocatalytic Acitivity Towards Oxygen Evolution Reaction

In the 21st century,the study of new energy is an important issue to the development of human society.Hydrogen energy become a hot spot of new energy because of its widely range of sources and pollution-free.Water electrolysis has great potential for hydrogen production due to its efficiently and high hydrogen purity.However,water electrolysis requires high overpotential and high energy consumes in industrial applications due to the high overpotential of oxygen evolution reaction?OER?.Therefor,developing high activity catalysts is the factor for water electrolysis,although traditional precious metal-based catalysts have excellent activity for OER,the large scale commercialized application of these catalysts are not practical because of the scarcity and high cost..Nickel-based compounds are promising candidates for replacing precious metal-based catalysts owing to their abundant reserves,low cost and high catalytic activity,Ni-Fe layered double hydroxide?LDH?is one of the most active OER catalyst in nickel-based compounds.However,preparation of efficient catalysts is severely restricted by their tendency to easy agglomeration.Variety preparation method needs to add a large amount of conductive agent and adhesive,reduce the OER catalytic activity and stability of the electrode.Anodization is a preparation method that can generate in-situ oxide film with good electrochemical performance in nickel substrate.The binding force between the anodic film and the substrate is strong and the impedance is low.In this study,nickel-based anodic film was used as precursor to obtain Ni₃S₂ nanorods grown vertically by sulfide hydrothermal treatment,the vertical Ni₃S₂ nanorods provide fast electrons transport path for OER.Ni-Fe LDH nanofilm was grown in the Ni₃S₂ nanorods by iron-doped hydrothermal,The Ni₃S₂@Ni-Fe LDH catalytic electrode with core@shell structure was obtained.The optimized hydrothermal parameters are as follows,sulfide hydrothermal:0.05M Na₂S and 0.1M NH₄F at 120?for 12h;iron-doped hydrothermal:1mM FeCl₃ 0.5M NH₄F solution at 120?for6h.The Ni₃S₂@Ni-Fe LDH electrodes prepared by the two-step hydrothermal were characterized in detail.The results showed that the microstructure of the vertically Ni₃S₂nanorods combined with Ni-Fe LDH nanosheets can promote the electrolyte infiltration and gas dissipation,provide a large number of catalytically active sites.Tredistribution of charge due to strong electronic interaction between Ni₃S₂ and Ni-Fe LDH occurred in Ni-Fe LDH,improve the intrinsic catalytic activity of Ni₃S₂@Ni-Fe LDH,The Ni₃S₂ nanorods were in-situ grown on conducting nickel substrate with strong adhesion strength,the impedance is low,the loss of film caused by gas flush are effectively avoid.Ni₃S₂@Ni-Fe LDH exhibited faster reaction kinetics,enhanced activity comparison with many other nickel-based catalysts,the Tafel slope of Ni₃S₂@Ni-Fe LDH was 35 mV dec^-1,and the overpotential at 10 mA cm^-2was 245 mV.Ni₃S₂@Ni-Fe LDH also exhibited high stability with OER overpotential only rised 5mV after 40 hours'water electrolysis at 10mA cm^-2.The preparation method and structure-activity relationship of the nickel-based electrode with high catalytic performance are expected to be extended to the research of other OER electrodes and provide the key material for the industrial application of hydrogen production from electrolysis.