Preparation Of NiFe LDH By DBD Microplasma For OER And Nonenzymatic Detection Of Glucose And H₂O₂

The applications of transition metals（Ni,Fe,Co,Mn,etc.）and their compounds in electrochemical energy storage and electrocatalysis have attracted more and more attention in recent years.Among these transition metals,Ni and its compounds emerge great potential as supercapacitor electrodes and electrocatalysts in alkaline media.Up to now,NiFe based oxides and hydroxides have been considered to be one of the most effective non-noble metal catalysts for OER（Oxygen Evolution Reaction）,and also an excellent electrochemical sensing electrode.Among these NiFe compounds,NiFe LDH（Layered Double Hydroxide）is one of the most widely used electrocatalytic materials due to its advantages of high specific surface area,more exposed active sites and faster electron transport.Inevitably,it has been the goal of researchers to modify NiFe LDH through a series of preparation and modification methods to make it possess more excellent electrocatalytic performance.In this project,several methods of preparation and modification of NiFe LDH based on DBD（Dielectric Barrier Discharge）microplasma are established.A new type of NiFe LDH and its compound with different morphologies and interlayer anions were prepared by using the advantages of more active sites and faster electron transport in the process of microplasma synthesis,which can be used for OER and non-enzymatic detection of glucose and hydrogen peroxide in alkaline conditions.The details are as follows:1.Fast and facile synthesis of carbonate-modified NiFe layered double hydroxide nanosheets by dielectric barrier discharge microplasma:mechanism and application in enhanced water oxidationNiFe LDH nanosheet-arrays modified by carbonate（Ci）were prepared on carbon cloth（CC）by DBD microplasma and the whole synthesis process can be completed in 1 h under normal temperature and pressure.The prepared NiFe LDH-CI/CC displays a fine catalytic activity for OER in alkaline medium.When the current density reaches 20 mA cm^-2,the overpotential of NiFe LDH-Ci/CC only requires 240 mV,and a good oxygen circulation frequency of 0.323 mol O₂s^-1is obtained at 350 mV.Subsequent direct emission spectra of nitrogen during DBD microplasma discharge were measured.It is proved that DBD synthesis process possesses high vibration temperature(T_vib,3100 K)and rotation temperature(T_rot,340 K),indicating that DBD synthesis process had high chemical reaction activity.In addition,the method also verified the formation of hydroxyl radicals（OH·）in the process of DBD synthesis,and then proposed the possible mechanism.2.Synthesis of CoO@NiFe layered double hydroxide by dielectric barrier discharge microplasma for oxygen evolution reaction in alkaline electrolyteA three-dimensional structure of CoO（cobalt oxide）nanoarrays was prepared on NF（Nickel Foam）.After that,CoO supported 3D NiFe LDH array was synthesized by DBD microplasma.The prepared 3D CoO@NiFe LDH/NF emerges a superior catalytic activity for oxygen evolving reaction（OER）in alkaline media,which only demands an overpotential of 225 mV at 20 mA cm^-2.The overpotential is among the best reported values for Ni-Fe based OER catalysts.The as-prepared electrocatalyst provides excellent long-term durability（>80 h）with a slight-decrease overpotential after 80 hours of continuous operation.Moreover,it exhibits a high turnover frequency（TOF）of 0.59 mol O₂s^-1at 350mV.3.Dielectric barrier discharge microplasma synthesis of self-support three-dimensional core-shell nickel iron hydroxide:To explore bifunctional function and high-sensitivity sensor for glucose and hydrogen peroxideNiFe LDH-CuO/CF（Copper Foam）with three-dimensional structure was successfully prepared by oxidation reaction at room temperature and DBD microplasma synthesis.The test data show that under the optimal conditions,the sensitivity of this sensor to glucose and hydrogen peroxide are 31591.0μA m M^-1cm^-2and 5199.3μA m M^-1cm^-2;the linear range are0.0004～2 mm and 0.001～4 mm;as well as the detection limits are 14 nm and 93 nm,correspondingly.In order to investigate the accuracy of the method,the method was applied to the determination of glucose and hydrogen peroxide in human serum and commercial fruit juice respectively.The result of test-data analysis is satisfactory.