Electrochemical Performances Of Plastic Polymer/Carbon Composite Electrodes For Environmental Engineering Applications

Electrochemistry offers promising approaches for the abatement of environmental pollutants due to its unique advantages,such as mild operating condition,adjustable redox capabilities,and amenability to automation.The large-scale application of electrochemical technologies for environmental engineering still needs applicable low-cost electrode materials urgently.In the present thesis,the polymer/carbon composite electrode（PCCE）,which had been applied to in-situ electroosmosis dehydration of dredging sludge,was studied systematically since its electrochemical performances was still unclear.The PCCE was prepared by a thermoplastic molding method using polyethylene/polypropylene and conductive graphite and carbon black powders as major constituents.The physical and electrochemical properties of the obtained PCCE was studied,and its prospect for environmental electrochemistry applications was explored.The measurement results revealed that the PCCE possessed light weight,high mechanical strength,good electrical conductivity and relatively high overpotentials for hydrogen and oxygen evolution reaction.The service lifetime of PCCE in aqueous solution was greatly influenced by the current density,the agitation condition of solution,and the thickness of electrode.At a low current density of 1 m A/cm²,planar PCCE could work as anode or cathode for approximately 100 hours,and the lifetime was longer when worked as cathode.Tubular PCCE,with wall thickness of 7.5 mm,showed enhanced stability in anodic electrolysis（more than 50 hours at a large current density of 10 m A/cm²）.The failure mechanism of PCCE can be explained by the debonding of conductive fillers.The conductive fillers shed from the polymer matrix due to stress of gas evolution,and the attachment of bubbles onto the surface of electrode also accelerated the failure by reducing the working area.The experiments for environmental application showed that the overall performance of PCCE can meet the requirements of electroosmotic dehydration and electro-Fenton process.Lead dioxide is an insoluble electrode with high oxygen evolution overpotential,good corrosion resistance and excellent electrical conductivity,but its preparation needs the use of high-cost precious metals.In this research,PCCE was used as cheap and available non-metallic conductive matrix to prepared PCCE/Pb O₂ electrodes by electrodeposition.PCCE/Pb O₂ electrodes were improved by introducing interlayer and doped elements.The results showed that PCCE/α/F^--β-Pb O₂ electrode had higher electrochemical stability.The interlayer ofα-Pb O₂ in PCCE/Pb O₂ electrodes enhanced the stability ofβ-Pb O₂ significantly.The size of Pb O₂grain was refined,and a dense surface thereby formed when F^-was used as dopant in the electrolyte.As a result,the electrochemical stability was promoted.Incorporation of PTFE caused a porous surface for PCCE/Pb O₂ electrodes.The performance of PCCE/Pb O₂ electrodes was affected by the current density and the time of deposition.The experiments showed that the best PCCE/α/F^--β-Pb O₂ electrode was obtained at the current density of 10 m A/cm² for 1hour electrolysis,with compact surface structure,suitable coating thickness and optimal electrochemical stability.The surface morphology of PCCE/Pb O₂ electrode was depended on the electrodeposition parameters,but the performance of oxygen evolution was less affected.The thickness of the Pb O₂ coating was positively correlated with the amount of charge,and suitable coating thickness brought the optimized stability.The experiments of environmental application revealed that PCCE/Pb O₂ electrodes can be applied to the electrochemical oxidation of organic pollutants.In a beaker experiment,77.3%of 2,4-DCP was removed after four hours of anodic electrolysis under the current density of 10 m A/cm².The performance of PCCE/Pb O₂ for oxidation degradation was comparable to Ti/Pb O₂.Therefore,as a low-cost and processable electrode material,PCCE is envisioned to be developed as an alternative to the conventional inert electrode materials for environmental electrochemistry applications.