Construction Of Electrode Based On Nickel Iron-based Layered Double Hydroxide For Hydrogen Production From Water Electrolysis

Hydrogen is a highly competitive and high-quality new energy.The technology of electrochemical water splitting to produce hydrogen has attracted attention due to its advantages of sustainability,cleanness and efficiency.It is divided into oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）.Due to slow kinetics,it is usually necessary to overcome high overpotentials to drive the reaction.Therefore,Electrocatalysts are needed to reduce overpotential and achieve efficient water splitting.At present,noble metal materials with high catalytic activity are still mainstream catalysts,but their cost issues limit their large-scale application.Therefore,the development of alternative and cheap transition metal catalysts has become one of the research hotspots.Among them,nickel iron-based layered double hydroxides（NiFe LDH）catalyst shows great developing value due to its low price and inherent superior activity.However,there are still some problems in this kind of catalyst,such as the catalytic activity is not ideal and poor conductivity.In this paper,NiFe LDH is used as the main body of research,and the defect engineering,interface engineering,derivatization and other strategies were used to regulate the surface interface of the catalyst and strengthen the mass transfer and diffusion,so as to improve the catalytic activity.In addition,a series of characterization techniques were used to study the changes in the phase and morphology of catalysts,and explore the catalytic reaction mechanism.The main research contents are as follows:（1）Construction of self-supported NiFe LDH nanosheet array electrode with superhydrophilic/superhydrophobic for hydrogen production from water electrolysis.NiFe LDH nanosheet grown on iron foam（NiFe/IF）was prepared by one-step hydrothermal etching method.The introduction of oxygen vacancy improves the intrinsic activity of the material,and the unique superhydrophilic/superaerophobic surface improves the utilization of the active sites.The prepared NiFe/IF shows excellent OER activity in 1 M KOH,its overpotential is only 245.2 m V at 100 m A cm^–2.And it shows excellent electrochemical activity and stability under simulated industrial conditions（6 M KOH and 85°C）.Based on the assembly of NiFe/IF as anode and cathode,the water electrolytic device demonstrates 1.57 V voltage at the current density of 10 m A cm^–2,and is assembled with a commercial solar cell to realize water splitting for hydrogen production by photovoltaic drive.（2）Construction of NiFe LDH/Fe₂O₃/Ni₃S₂/IF heterojunction electrode for hydrogen production from water electrolysis.Self-supporting NiFe LDH/Fe₂O₃/Ni₃S_2（2）/IF heterostructure based on NiFe LDH were prepared by self-corrosion and hydrothermal strategy.Benefiting from the constructed 2D/0D hierarchical heterostructure,NiFe LDH/Fe₂O₃/Ni₃S_2（2）/IF not only exposes more active centers,but also accelerates the charge and mass transfer.Therefore,it shows superior OER and HER activities.The overpotentials of OER and HER only requires 226.2 and162.8 m V at current density of 100 m A cm^–2.The catalyst was used as both cathode and anode to assemble a device for overall water splitting,and it only need 1.55 V voltage at 10 m A cm^–2.The device also can be coupled with a solar cell to realize hydrogen production from water electrolysis.（3）Construction of crystalline/amorphous NiFe LDH derived electrode for hydrogen production from water electrolysis.The crystalline NiFe P/amorphous P-doped Fe OOH heterostructure（P-NiFe O_xH_y/IF）derived from NiFe LDH was prepared by means of self-corrosion and calcination.Its rich crystalline/amorphous interface and amorphous region containing a large number of unsaturated metal atoms and defects can adjust the local electronic structure and promote the charge transfer process.Therefore,P-NiFe O_xH_y/IF shows excellent performance under alkaline conditions.It just needs overpotentials of 20.8 m V and 159.2 m V at 10 m A cm^-2 for HER and OER,respectively.The results of in-situ Raman spectroscopy also proved that P-NiFe O_xH_y/IF can rapidly reconstruct structure in a strong oxidation environment and promote the formation of the active Ni OOH species.In addition,P-NiFe O_xH_y/IF,as a bifunctional electrocatalyst,is assembled as two-electrode electrolyzer for water electrolysis,it only takes 1.537 V to reach 10 m A cm^–2,and it can be used with a commercial solar cell to realize hydrogen production from water electrolysis.