| Electrolysis of water is a promising method for high efficiency hydrogen production technology.In the process of electrochemical water splitting,oxygen evolution reaction（OER）OER is the bottleneck step owing to its slow kinetic process.Therefore,it is urgent to develop high-performance OER catalysts to reduce the energy barrier,achieving low overpotential water splitting.Among all kinds of OER electrochemical catalysts,Ni Fe-based catalyst is considered as a promising non-noble metal anode electrocatalyst in alkaline medium because of its low cost,high conductivity and catalytic activity.Ni Fe layered double hydroxide（Ni Fe LDH）owns great potential in OER electrocatalytic performance which dues to its unique layered structure and the interaction between Ni and Fe.However,the poor intrinsic conductivity and low catalytic activity limit its wide application in OER.Therefore,reasonable structure control strategy and heterostructure construction can be used to solve these problems.Aiming at structural control strategy,the introduction of heteroatoms can increase the number of active sites,optimize the electronic structure and local coordination environment,thus the weak catalytic activity problem of the basal surface can be solved.For the heterostructure construction strategy,such as introducing carbon-based conductive material or substrate,can effectively promote electron transfer and increase the contact area between the material and electrolyte medium,which may contribute to the improvement of electrocatalytic performance.Based on the above background,the electronic structure of Ni Fe LDH is regulated by introducing heteroatoms.In addition,the synergistic effect of in-situ growth and heterostructure construction realizes the efficient electrocatalytic water splitting by using Ni Fe-based bimetallic hydroxide.Furthermore,the structure-activity relationship between each component is revealed,which provides theoretical basis for the development of new electrocatalysts.The main research contents and innovations are as follows.In this paper,nickel-iron base Layered double hydroxides were synthesized by hydrothermal method.and the catalytics activity were improved by cation doping and combining with conductive materials.At the same time,the corresponding electrocatalytic ability of OER was investaged in detail.Firstly,the Zn2+doped Ni Fe LDH was synthesized by one-step hydrothermal method,and its OER catalytic performance was studied.It was found that Zn2+doping induced the phase change of Ni Fe LDH（from hexagonal phase to oblique hexagonal phase）.Addtionaly,Zn2+doping improved the electrocatalytic performance of Ni Fe LDH.Among them,Ni10Fe2Zn1 exhibited the best electrocatalytic OER performance in alkaline environment.When the current density was 10m A·cm-2and the loading concentration was 1.0 mg·cm-2,the overpotential of Zn-Ni Fe LDH electrode was 218 m V.When the current density was 10 m A·cm-2and the loading concentration was 0.60 mg·cm-2,the overpotential of Zn-Ni Fe LDH electrode was 158 m V.Furthermore,the Zn-Ni Fe LDH catalytic electrode showed excellent stability in the constant current test of 50h 100m A·cm-2.Meanwhile,the comparative analysis by transmission electron microscopy（TEM）,scanning electron microscopy（SEM）and x-ray photoelectron spectroscopy（XPS）showed that the improvement of OER catalytic activity of Zn-doped Ni Fe LDH,can be attributed to the change of crystal phase and the optimization of electronic structure after doping.Furthermore,the increase proportion of Ni3+in Ni Fe LDH improves the intrinsic activity of the catalyst,which accelerated the kinetic process of electrocatalytic OER reaction.Secondly,the Fe3O4@Ni Fe LDH nanocomposite was grown in situ by template method and used for electrocatalysis of OER reaction.The introduction of Fe3O4 nanoparticles effectively Modified the electronic structure of Ni Fe LDH surface,which improved the abundance of metal atoms with high valence state and promoted the performance of OER.To solve the problem of poor intrinsic conductivity of Ni Fe LDH,the nanocomposite was further combined with conductive substrate.Besides improving conductivity,the presence of substrate also effectively reduces the size of Ni Fe LDH,thus improves the stability and electrocatalytic activity of electrode materials.In addition,the large pore size structure of the self-supporting conductive substrate is benifical for the ion diffusion and the release of bubbles.Electrochemical test showd that the overpotential of Fe3O4@Ni Fe LDH/IF is only 207 m V and the Tafel slope is 28.27 m V·dec-1 when the current density reaches 30 m A·cm-2.More importantly,it can maintain excellent stability for 100 h under the constant current test of 1.0 A·cm-2,which greatly benefits the development of industrial catalyst. |
