The Fabrication Of Fe-doped Ni₃S₂ And Their Performance Study In Oxygen Evolution Reaction

In the process of water electrolysis,oxygen evolution reaction（OER）is a four-electron transfer process,and the potential of the electrolysis water is higher.Although precious metals show advantages in oxygen evolution potential,their high price and low surface content limit their practical applications.So researchers pay more attention to transition metal.For example,transition metal sulfide and oxide are favored for their excellent catalytic activity and high electrochemical stability.Specially,nickel sulfide are especially promising due to their excellent conductivity and good electrocatalytic activity.In recent years,Ni₃S₂ also have been accepted to be applied as one of promising OER candidates,Considerable efforts should be devoted to develop the higher performance and stability based on it.Strategies have been developed for regulating the catalytic activities of electrocatalysts,including（i）the doping of foreign atoms and（ii）amorphous engineering to increase the number of active sites.Herein,Fe-doped Ni₃S₂ on the nickel foam was synthesized by a two-step hydrothermal method.It was found that doping of foreign atoms could improve catalytic activity and stability for Ni₃S₂.Based on Fe-doped Ni₃S₂,by changing the concentration of the reaction solution tune the degree of disorder.XRD and HRTEM were applied to illustrate that the disorder degrees were gradually decreased with the concentration of the reaction solution decreased.From the SEM and TEM images,the morphology evolution was observed from nanosheets to nanobulks with degree of disorder decreased.It was found that the catalyst has abundant active sites and high conductivity due to its proper disorder degree.Fe-doped Ni₃S₂/NF was prepared as OER electrocatalyst by two-step hydrothermal method.Through a series of physical characterization and electrochemical measurement,we have discussed the relationship between OER catalytic activity and disorder degree for Fe-doped Ni₃S₂/NF.With the degree of disorder increased,catalytic activity was increased.Notably,further degree of disorder limit the tendency of catalytic activity,own to higher degree of disorder decrease its conductivity.The facile amorphous degree lead to the abundant active sites and higher conductivity.In our experiment,the optimized catalyst has a small overpotential of 295 mV,and the current density of 10mA cm^-2 in 1.0m KOH,and the corresponding Tafel slope is 71 mV dec^-1.It also has good electrochemical stability.