The Preparation Of β-PbO₂-SPE Composite Membrane Electrode By Impregnation-oxidation Method

SPE composite membrane electrode has been becoming the frontier of electrochemical material field due to its simple media condition, higher current efficiency, the lower energy consumption, the less side-reaction, the wider operation range and the outstanding electrocatalytic active. All now manners of making PbO₂—SPE composite membrane electrode can be calssified into two categories, One is the mechanical method, and another is electrochemical method. These two methods have their advantages and, simultaneously, have their shortness. So, a completely new plan, impregnation-oxidation method, was put forward to and was used to prepare PbO₂—SPE composite membrane electrode, the concept is to directly depositβ-PbO₂ in the basal membrane by the electroless method. As a new researching item, supported by He'nan Outstanding talent innovation fund (No: 521001400), this work has been done a lot, it included: to choose the types of basal membrane material, to research the activating method of basal membrane, to optimize the preparing technical and the technology conditions, to characterizes electrode performance, to modify and evaluate electrode performance and research the effect in degradation phenol. All the research will be valuable in the academic filed and is very useful in the industrial project.The basal membrane is the basement to prepare good composite membrane electrode material. According to the special structure of Nation basal membrane, based on the clearing and swelling processes, and by means of the analyses of SEM and EDS, the experimental results declared that Nafion324 positive ionic membrane was the ideal basal membrane material in preparingβ-PbO₂—SPE composite membrane electrodes. The methods and steps to active basal membrane were decided and the conditions to swell cleared Nation324 well were obtained too. Based on the conclusions of the five impregnation-oxidation programs, the technical sheet to prepareβ-PbO₂—SPE composite membrane electrodes was determined. Through the detailed processes analyses to depositingβ-PbO₂ in basal membrane and entirely single factor experiments, the author firstly optimizes the conditions in preparingβ-PbO₂—SPE composite membrane electrodes. The impregnating conditions are: stirring is proceeded in ultrasonic wave, the impregnating temperature is kept at 50℃, the better impregnating solution component is 0.05 mol·L^-1 Pb(NO₃)₂+1.0 mol·L^-1 NH₄Ac, and the impregnating time is 2.0 h; the oxidation conditions are: the stirring strength of ultrasonic wave is 40W, the oxidation temperature is 40℃and the oxidation time is 2.0 h. Under all the conditions, a completeβ-PbO₂—SPE composite membrane electrode can be prepared out by repeating the impregnating-oxidation processes for 8-11 times, the characterization results ofβ-PbO₂—SPE composite membrane electrode are as follows: The X-ray diffraction result shows that the main composition of plating layer isβ-PbO₂. Theβ-PbO₂ crystal particle is fine and tightly deposited in Nation324 basal membrane. The SEM diagram and the EDS analysis declare that the plating layer ofβ-PbO₂ is compact and uniform in basic membrane. The polarization curve demonstrated, in 1.0 mol·L^-1 H2SO₄ solution, thatβ-PbO₂—SPE composite membrane electrode oxygen evolution voltage is 100mv (vs. SCE), and the exchange current density i⁰=7.182×10^-3A·cm^-2, and theβ-PbO₂ layer has good stability and anti-corrosion. The cyclic voltammogram (CV)curves of phenol solution onβ-PbO₂—SPE composite membrane electrode demonstrated that the electrode has capability in degradation phenol, and the degradation processes of phenol on membrane electrodes were quasi-reversibility and were controlled by diffuse processes.According to the roles of additive agents in electroless plating technical, the inorganic additives F^-,Fe²⁺ and Co²⁺ were introduced in impregnation process and to obtained three kinds of modificationβ-PbO₂—SPE composite membrane electrodes. Though the tests by XRD,SEM,EDS,the polarization curves and CV curves, the results showed thatβ-PbO₂ layers in modifiedβ-PbO₂—SPE composite membrane electrodes are more uniform and compact than normalβ-PbO₂—SPE composite membrane electrodes, and the active and stable of composite membrane electrodes are improved so that the modifiedβ-PbO₂—SPE composite membrane electrodes are more suitable for anodic materials. The roles of the three additive agents in depositing processes ofβ-PbO₂ were preliminary discussed, the conclusions are: the F^- is only to change the depositing form of plating layer, Fe²⁺ and Co²⁺ can be oxide intoα-Fe₂O₃ and Co₃O₄ and commonly deposited withβ-PbO₂ in Nation324 membrane, so that, the modifiedβ-PbO₂—SPE composite membrane electrodes have better the electrocatalytic active than normal electrode.The experimental results showed that, in 1.0 mol·L^-1 H₂SO₄ solution, and the content of phenol is 100mg·L^-1, normal and modifiedβ-PbO₂—SPE composite membrane electrodes have stronger degradation power. The order of degradation power is:β-PbO₂/ Co—SPE＞β-PbO₂/Fe—SPE＞β-PbO₂—SPE≈β-PbO₂/F—SPE. The tank voltages, at above processes, are lower than other PbO₂ electrodes in nearly same operating conditions. This result is benefitial in decreasing electricity consumption and increasing current efficiency, and it is the reason to prepareβ-PbO₂—SPE composite membrane electrode. The order also demonstrates that the goodβ-PbO₂—SPE composite membrane electrodes can be obtained when the additive agents were introduced in impregnation-oxidation processes.