Preparation Of Nickel-based Layered Double Hydroxide Materials And Their Electrocatalytic Oxygen Precipitation Properties

The excessive use of fossil energy has led to serious environmental pollution around all the world,and the increasing population and the rapid improvement of people's quality of life have led to rapid growth in global energy demand,so there is an urgent need to develop an efficient and clean energy.In such background,the "hydrogen economy" came into being.However,the development of electrolyzed water technology for generating hydrogen has hindered due to its low efficiency,high energy consumption and high cost.The oxygen evolution reaction involves a four-electron transfer process with slow reaction kinetics and is a ratelimiting step in the overall water splitting process.The noble metal-based electrocatalyst has excellent catalytic performance and can effectively reduce the overpotential required to carry out the oxygen evolution reaction,but their reserves and cost problems limit its development.Among alkaline electrolytes,transition metal-based materials exhibit excellent water oxidation catalytic activity and stability.Layered double hydroxide materials have the advantages of diversified metal species and stable two-dimensional layered structure,and are one of the most promising water oxidation electrocatalysts.Based on the typical structural characteristics of layered double hydroxide materials,this paper improves the catalytic performance of materials by adjusting components and forming a composite.Whether it is component optimization or the formation of composite materials,their essence is to optimize the energy required for the adsorption and desorption of the reaction intermediates by adjusting the coordination environment of the active sites.In addition,the improvement in the synthesis method can adjust the amount of active sites exposed on the surface of the material to optimize catalyst activity.The specific content of this paper is as follows:(1)NiFe-LDH containing a tungstate anion was synthesized in one step using a flash nano-precipitation method.The water oxidation catalytic performance of the material is optimized by adjusting the anion composition in the LDH material.Electrochemical results show that the introduction of tungstate anion improves the charge transfer capacity and catalytic activity of the material.Compared with the traditional coprecipitation method,the flash nano-precipitation provides rapid micro-component mixing to enhance the uniformity of the reaction system,thereby forming a uniform active material.This work confirmed the promotion of metal oxyanion on the electrocatalytic activity of LDH.In addition,it provided a new synthesis method for transition metal-based materials.(2)Both layered double hydroxide materials and polyoxometallates are excellent water oxidation catalysts.In this work,a phosphotungstic acid was used as an example to synthesize NiFe-LDH intercalated partially with metal-oxygen clusters.The material exhibited good catalytic activity and stability of oxygen evolution reaction.The analytical results show that the material has an improved intrinsic activity and exhibits improved electrocatalytic performance in the reduced density of contactable active sites.This work has opened up the research of LDH-POM intercalation assembly materials as electrocatalysts,which provides a new strategy for optimizing the electrocatalytic activity of LDH-based materials.