Synthesis And Electrocatalytic Performance For Oxygen Evolution Of Nickel Based Nanomaterials

Due to the excessive consumption of fossil fuels which has caused energy crisis and a series of environmental pollution problems,hydrogen energy has been paid more and more attention.Among all the methods for hydrogen production,electrochemical water splitting is the most promising strategy due to the high purity of the product hydrogen and pollution-free process.Electrocatalytic-water-splitting systems consist of hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Compared to HER,OER limits the development of this technology due to the sluggish kinetics.Nowadays,Iridium oxide(Ir O₂)and Ruthenium oxide(Ru O₂)are considered to be the best OER catalysts,but the low abundance and high cost make it impossible for widespread application,so it is necessary to explore cheap and efficient OER electrocatalysts.In this paper,a series of high efficiency nickel-based OER catalysts were prepared and the catalytic mechanism was studied.The main research contents are as follows:(1)W doped Nickel sulfide(W-Ni₃S₂/Ni₇S₆) was prepared by a W-doping-induced phase transition strategy,which effectively improved the electrocatalytic OER performance of nickel sulfide.W could adjust the morphology of the catalyst to form uniform nanorod arrays,and induce the Ni₃S₂phase to transform into Ni₇S₆.The interface between Ni₃S₂and Ni₇S₆provided abundant active sites and improved the charge transfer rate.What's more,W could also adjust the electronic structure of Ni and enhance the activity of W-Ni₃S₂/Ni₇S₆.The overpotential of 100 and 200 m A·cm^-2was only 202 and 285 m V,so W-Ni₃S₂/Ni₇S₆was an excellent OER catalyst.This work not only provided an effective strategy for the construction of heterojunction,but also provided a new perspective for the construction of advanced heterojunction electrocatalysts at the atomic level.(2)Trimetallic metal-organic frameworks catalyst with defects(Ni Co_1.08BDC-Fc_0.24)was prepared by a solvothermal method,we found it that the electronic structure of Ni was adjusted,simultaneously thanks to the flexible structure of metal-organic frameworks(MOFs),we used the method of replacing ligand to prepare our catalysts,which could provide abundant active sites and accelerate the kinetic process of the reaction effectively.Finally,the resulting catalyst showed the excellent OER activity with ultralow overpotential of 278 m V at current density of 100 m A·cm^-2.This work provided a new strategy for regulating the electronic structure of MOFs to obtain efficient electrocatalysts.(3)Nickel hydroxide/hydroxyl iron oxide heterojunction catalyst was prepared by solvothermal method and electrochemical deposition method,we found it that Fe could adjust the electronic structure of Ni,which enhanced the intrinsic activity of Ni,and the interface between nickel hydroxide and hydroxyl iron oxide promoted the effective transfer of substance and improved the charge transfer rate,thereby we got an efficient OER catalyst.The overpotential of 100 m A·cm^-2was only 270 m V,and Nickel hydroxide/hydroxyl iron oxide heterojunction catalyst showed excellent stability.In this work,the interfacial charge of the heterojunction catalyst was adjusted by using the relationship between structure and activity of the catalysts to enhance the electrocatalytic performance,which provided a new idea for the development of efficient electrocatalysts.