Preparation And Properties Of Zinc-Containing Double Hydroxide-based Electrocatalysts

Due to the potentially huge energy crisis and the environmental problems that must be faced,the search for renewable energy has become a hot focus on the hands,and there is an urgent need to find green,clean,alternative,cheap and sustainable new energy sources to supply the development of human civilization.It is the most eye-catching high-efficiency and environmentally friendly energy source,and the production of hydrogen by electrolyzed water is the top priority.Hydrogen energy is the most attractive high-efficiency environmental protection energy source,and hydrogen production from electrolyzed water is the most important among them.At present,RuO2 or IrO2-based catalysts in the field of oxygen evolution reaction and Pt-based precious metal catalysts in the field of hydrogen evolution reaction have the most excellent performance,but the precious metal has low crust reserves,high cost,easy attenuation and difficult to apply at high current density Limited practical application.Researchers are committed to solving various problems with the application of hydrogen energy.One of the challenges is to find an efficient,stable,and cheap electrocatalyst for water cracking,which has great research significance.Many studies have shown that layered double metal hydroxides(LDHs)exhibit excellent oxygen evolution reaction(OER)performance and hydrogen evolution reaction(HER)performance due to their laminar ion variability,interlayer anion exchangeability and the ability to provide a larger reaction surface.Transition metal layered double metal hydroxides(Co,Ni,Fe,Mn,V,etc.)has been widely studied.Nickel-based double metal hydroxides have been the focus on researchers because nickel has multiple oxidation valence states and can reduce the reaction barriers of the water cracking reaction.This study investigated the electrocatalytic performance of nickel-zinc layered double metal hydroxides and their derivatives.We use different solvents to adjust the surface structure and use it as a precursor of phosphate and sulfurizing to design more efficient electrocatalysts.In this paper,two water-splitting electrocatalysts of Ni(?,?)Zn-LDH/NF-nm and Ni3S2/NF-np were designed and synthesized.The surface structure of the catalyst,the relationship between the formation mechanism and the material,and performance was discussed in depth.The main research conclusions of this paper include the following two parts:(1)Using methanol as a structural regulator,Ni3+-doped ultra-thin NiZn-LDH nanomesh(Ni(?,?)Zn-LDH/NF-nm)were prepared through a one-step hydrothermal process.The formation mechanism of NiZn-LDH was discussed.The phase,structure,crystallinity,and surface chemical valence of the samples after OER and HER tests were also investigated.The results show that the phase changes after OER and some zinc ions are released to form defects and the material has a significant contribution to reducing the OER reaction barrier.The prepared Ni(?,?)Zn-LDH/NF-nm has relatively low overpotentials of 320 and 370 mV when driving large current densities of 100 and 500 mA cm-2,respectively,which is far superior to RuO2/NF.At the same time,a Ni(?,?)Zn-LDH/NF-nm sample was used as the cathode and anode to assemble a fully hydrolyzed electrolytic cell,which showed excellent catalytic activity and stability.(2)Using Ni(?,?)Zn-LDH/NF-nm material as a precursor,Zn-doped defect-rich coral flower-like Ni3S2 material(Zn-Ni3S2/NF-np)was synthesized by the solvothermal method.In the solvothermal process,thioacetamide continuously releases SH-ions to leaching part of Zn.The material not only has the nanopore structure of the precursor but also has new defective active sites.The material has a large number of defective structures and nanoporous structures to enhance the intrinsic activity,increase the large electrochemically active surface area,and faster charge transfer,so it exhibits excellent HER performance and OER performance.When this material is used as an electrode for electrocatalytic hydrogen production,it can drive larger current densities(100 mA cm-2,500 mA cm-2,and 1000 mA cm-2)at lower overpotentials(145 mV,235 mV,and 290 mV),and can work stably for at least 60 h at an over-potential of-1.3 V.When used as an electrocatalytic oxygen-generating electrode,it only needs 0.34 mV and 0.4 mV overpotentials to drive 100 and 500 mA cm-2,respectively,and can be used stably at 0.5 V for 70 h.