| In recent years,PbO2 electrode materials have become one of the most widely studied and applied anode materials for the treatment of dye wastewater due to their excellent electrical conductivity,high electrocatalytic activity,strong corrosion resistance and low cost.Therefore,this research aimed to the problem of low efficiency of electrocatalytic treatment of bio-refractory organic wastewater,the preparation and electrochemical performance of the two-dimensional macroporous array?-PbO2 electrodes and its electrocatalytic degradation of methyl orange were analyzed.A novel two-dimensional?-PbO2 macroporous array electrode?2D-PbO2?was fabricated by electrochemical deposition based on a two-dimensional colloidal crystal template,which was constructed using the Langmuir-Blodgett film technique.Based on this template combined with anodization to deposit the?-PbO2 micron layer,and then remove the PS microspheres by demolding,and finally perform the second deposition of?-PbO2 to obtain the target electrode material.The structure and surface morphology of 2D-PbO2 electrodes and traditional flat electrodes?Flat-PbO2?were characterized by scanning electron microscopy?SEM?and X-ray diffraction?XRD?.The results show that the 2D-PbO2electrodes exhibited a two-dimensional ordered micron spherical cavity array structure with a large specific surface area,which affects the preferred growth orientation of ?-PbO2 crystals.The coating surface is composed of single ?-PbO2 microcavities 5-6?m in size,and the spacing of the micron holes is approximately 2?m,and the average grain size is 128?.The anode polarization curves?LSV?,cyclic voltammetry curves?CV?and electrochemical impedance spectroscopy measurements?EIS?were investigated to compare the electrocatalytic performance and corrosion resistance of the two kinds of electrodes.Compared with the Flat-PbO2 electrodes,the 2D-PbO2 electrodes show a higher exchange current density(j0=1.478×10-5A·cm-2),smaller apparent activation energy(Ea=12.09kJ·mol-1),larger electric double layer capacitance(Cdl=60.00?F·cm-2)and smaller charge transfer resistance(Rct=16.89?·cm2)in 0.05mol·L-1Na2SO4 solution,resulting in better electrocatalytic performance.At the same time,compared with the traditional Flat-PbO2electrodes,the 2D-PbO2electrodes has a larger self-corrosion potential(Ecorr=0.993V),a smaller self-corrosion current(Icorr=2.466×10-6A·cm-2),a larger charge transfer resistance(Rct=4.983×104?·cm2),and a significantly improved stability and corrosion resistance.The effects of degradation temperature,degradation current density,pH value of the degradation solution,and the concentration of chloride ion in the degradation solution on the degradation of methyl orange were determined by UV-visible spectrophotometry,and explored the influence of various factors on the degradation process of methyl orange.The optimal process parameters for the electrocatalytic degradation of methyl orange were clarified as follows:200mL methyl orange simulated azo dye wastewater A[MO+Na2SO4],the temperature was maintained at 25?,the current density was controlled at 50mA·cm-2,the chloride ion concentration was 0.02mol·L-1,pH=7,and the magnetic stirring speed was200r·min-1 The electrode spacing is 3cm and the degradation time is 180minutes.The results show that the electrocatalytic degradation reaction followed pseudo first-order kinetics?n=0.9949?,and the reaction rate constant value(k=32.68×10-3min-1)was 1.38 times greater than that of Flat-PbO2 electrodes(k=29.02×10-3min-1),the electrocatalytic degradation efficiency is significantly improved,and the electrocatalytic degradation performance is excellent.The cyclic voltammetry curve?CV?was used to analyze the electrocatalytic degradation of methyl orange at the 2D-PbO2 electrodes,and the mechanism of methyl orange degradation was initially discussed in combination with UV-visible absorption spectroscopy?UV-Vis?and high performance liquid chromatography?HPLC?.The electrocatalytic degradation of methyl orange on the 2D-PbO2 electrodes is mainly accomplished by the direct electrochemical oxidation of the azo bond of the conjugated chromophore to form the intermediates N,N-dimethyl-p-phenylenediamine and sulfonamide.This intermediate is further cracked into intermediates with smaller molecular weight,finally converted into CO2 and H2O,to achieve the degradation of methyl orange. |
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