Titanium-based Porous Lead Dioxide/manganese Ruthenium Oxide Gradient Composite Anode

At present,the anode used in zinc electrowinning is mainly lead-silver alloy,and the anode has many defects in use,such as high oxygen evolution potential,low mechanical strength,and dissolution of lead.In addition,if the electrolyte contains a relatively high concentration of chlorine and fluoride ions,it will corrode the lead alloy anode and shorten the service life of the lead alloy anode in the zinc electrowinning process.Therefore,in order to prepare high-activity,long-life anode material for zinc electrowinning,a series of research and tests were carried out,and finally a titanium-based porous lead dioxide/manganese antimony oxide gradient compositeanodewasobtained.Ti/Sn-Sb-Ru Ox/?-PbO₂and Ti/Sn-Sb-Ru Ox/?-PbO₂/MnO₂-RuO₂composite electrodes with titanium as matrix were prepared by electrodeposition and thermal decomposition.In this paper,the best porous Ti/Sn-Sb-Ru Ox/?-PbO₂electrode was obtained by studying the tin-antimony-ruthenium oxide underlayer and current density and then the best porous electrode was used as the research object.By studying the concentration of Mn²⁺,H₂SO₄and the thermal decomposition temperature of manganese nitrate coating solution in ruthenium-containing manganese sulfate solution to obtain the optimal gradient Ti/Sn-Sb-Ru Ox/?-PbO₂/MnO₂-RuO₂composite electrode.The surface morphology of the prepared coating was analyzed by scanning electron microscopy(SEM).The phase composition of the prepared coating was analyzed by X-ray diffractometry(XRD).The prepared composite electrode was tested by anodic polarization curve(LSV),electrochemical impedance spectroscopy(EIS),cyclic voltammetry curve(CV)and constant current polarization curve using an electrochemical workstation,and finally,various electrode lifetimes were tested by accelerated life corrosion experiments in the sulphuric acid solution containing 2g/L Cl^-.The results and conclusions obtained are as follows:When the Sn:Ru=8:1 in the preparation of the underlying tin-antimony-ruthenium oxide coating and current density is 2 A/dm²,under this condition,the lead dioxide prepared by electrodeposition on the bottom surface is in a porous structure state and uniform pore size,the surface roughness is the largest,and the active area is the largest.XRD shows that the main phase is?-PbO₂.The electrochemical analysis shows that the oxygen evolution potential is the lowest and the electrocatalytic activity is the best;It has a long life of about 71 h in the sulfuric acid solution containing 2 g/L Cl^-.The electrodeposition mechanism of porous lead dioxide was proposed.During the process of lead dioxide deposition,·OH adsorbed on the electrode surface to form oxygen,and Pb²⁺was deposited as a template by oxygen bubble.The doping of Fe³⁺in the bath increased the deposition rate of PbO₂and reduced the effect of internal stress of?-PbO₂.In the process of electrodeposition of manganese niobium oxide on the surface of porous lead dioxide,the lead dioxide is partially dissolved in the ruthenium-containing manganese sulfate solution.Co-deposited with the manganese-ruthenium oxide on the surface of the lead dioxide to form a gradient co-solid solution.When the concentration of Mn²⁺is 40 g/L,the surface of the obtained manganese-ruthenium oxide electrode is densely packed,and the unit cell is relatively small.The electrochemical test results show that the oxygen evolution potential of the composite electrode is low and the catalytic activity is good.It has a long life of about 97 h in the sulfuric acid solution containing 2 g/L Cl^-.When the concentration of sulfuric acid is 20 g/L,the surface of the obtained manganese-ruthenium oxide electrode is densely packed and the active area is large.The electrochemical performance test shows that the oxygen evolution potential is the lowest and the catalytic activity is the best.The longevity in a sulfuric acid solution containing 2 g/L Cl^-is up to 95 h.The thermal decomposition temperature is controlled at 290°C,and the prepared Ti/Sn-Sb-Ru Ox/?-PbO₂/MnO₂-RuO₂anode has the longest life.It can be seen from the surface morphology that the thermal decomposition process destroys the crystal structure of the porous lead dioxide,so that the stability of the entire electrode is lowered.