Zinc Electrowinning Preparation And Properties Of Poly 3,4 - Ethylenedioxythiophene / Polyaniline Composite Anode Materials

Lead-based alloy anode is always used as insoluble anode in zinc electrodeposition industry. However, there are several problems on such anode, for example:high oxygen evolution overpotential, poor corrosion resistance, low mechanical strength, easy to creeping deformation and short circuit. And the surface active layer of PbO2 is easy to falling off, generating the anode mud and decreasing of the quality of the cathode zinc. In order to deal with these shortcomings of the lead-based anode, many different kinds of anodes are developed by domestic and foreign researchers. But due to high cost, short life and processing problems, they fail to realize industrialization. Therefore, it is a hot topic to research and development of new energy saving anode in zinc electrolytic field.PEDOT with the regular structure, high conductivity, environmental stability and excellent electrochemical performance will be an ideal anode material. In this paper, the PEDOT, PEDOT/PANI and PANI/PEDOT composite materials were prepared by in-situ polymerization method, the polymerization mechanism of composites were studied and the optimal synthesis conditions based on electrical conductivity and electrochemical performance were explored. In the same time, electrochemical performances of the anodes were studied in H2SO4-ZnSO4 electrolyte. Compared with performances Pb-Ag(1%wt) alloy anode such as oxygen evolution potential, cell voltage, current efficiency and electrode life, the electrochemical property of the polymer anodes were discussed systematically.The microstructure, crystal phase, morphology and thermal stability of synthesized materials were characterized by means of FITR, XRD, SEM and thermal analysis and so on. The electrochemical properties of anodes were also studied by line sweep voltammetry, AC impedance, cyclic voltammetry, Tafel plot and oxygen evolution potential. The main results are as following:(1) The optimal synthesis conditions of PEDOT are:[EDOT]=0.6mol/L, [composite oxidant]=0.6mol/L(FeCl3:APS=1:1), [composite emulsifier]=0.4mol/L (SDBS:CTAB=3:2), [composite doping agent]=1.2 mol/L(H2S04:SSA=4:1);(2) The optimal synthesis conditions of PEDOT/PANI are:EDOT solution includes [EDOT]=0.6mol/L, [composite oxidant]=0.6mol/L(FeCl3:APS=1:1), [composite ernulsifier]=0.4mol/L(SDBS:CTAB=3:2), [composite doping agent]=1.2mol/L (H2SO4:SSA=4:1); After two hours, Aniline solution is added. And then, Aniline solution includes [An]=0.8mol/L, [APS]=0.6mol/L, [composite emulsifier]=0.3mol/L (SDBS:CTAB=4:2), [composite doping agent]=0.6mol/L (H2SO4:SSA=5:1);(3) The optimal synthesis conditions of PANI/PEDOT are:Aniline solution includes [An]=0.5mol/L, [H2SO4]=0.8mol/L, [SSA]=0.2mol/L, [SDBS]=0.2mol/L, [CTAB]=0.2mol/L, [APS]=0.6mol/L; After two hours, EDOT solution is added. EDOT solution includes [EDOT]=0.6mol/L, [composite oxidant]=0.6mol/L(FeCl3:APS=1:1), [composite emulsifier]=0.2mol/L(SDBS:CTAB=1:1), [composite doping agent]= 0.6mol/L(H2SO4:SSA=4:1);(4) PEDOT/PANI composite material is a kind of core-shell polymer with the core of the chain of PEDOT and shell of the chain of PANI. PANI/PEDOT composite material is a kind of grafted copolymer with short chain of PEDOT is grafted on the chain of PANI.(5) The electrical conductivity and catalytic activity of PEDOT anode were superior to the PEDOT/PANI and PANI/PEDOT composite anodes in zinc sulfate-sulfuric acid electrolytic system. For PEDOT anode, the stability is best, the circulation current-voltage response is largest and the current capacitive is largest. But the corrosion resistance of PEDOT/PANI composite anode is the best.(6) At the current density of 0.05 A/cm2, oxygen potential, slot voltage and electrode life of the Pb-Ag (1%wt) is 1.856V,3.35V and 2.56 years; PEDOT is 1.483V, 2.83V and 1.94 years; PEDOT/PANI is 1.513V,2.87V and 1.75 years; and PANI/PEDOT is 1.573V,2.93V and 1.56 years. The oxygen potential, slot voltage and energy consumption of PEDOT and its composite anodes are less than Pb-Ag (1%wt) alloy anode.(7) The main reasons of deactivation for polymer anodes are that creep deformation happened to the anode because of the internal residual stress. In addition, the anodes in the acidic system for a long time, are expanded by the molecules infiltrated. And the cracks are emerged on the surface make the force of electronic transfer bigger.