Study On The Structure And Characteristics Of Ti-based Metal-oxide Electrodes With Sb-SnO₂ Intermediate Layers

Electrochemical technology is used in many fields,such as chemical power, electroplating,electrometallurgy,inorganic and organic electrosynthesis,corrosion protection,waste water treatment,nano-materials preparation,etc.The electrode materials are obviously the heart of any electrochemical process,which can affect the reaction products,the process efficiency,the energy consumption and feasibility.Therefore,the study and development of electrode materials,especially the anodes used in acidic solution, is of significance in industrial electrochemical technology.The study was mainly focused on the DSAs(Dimensionally Stable Anodes),which consisted of the base of Ti,the intermediate layers of Sb-doped SnO₂ and active coatings. The intermediate layers of Sb-doped SnO₂ were prepared by a polymeric precursor method (PPM).Three kinds of active coating,the oxides of Pb or Sn or Mn,were prepared,and the microstructure and characteristics were also investigated.Three different deposition methods were employed to prepare PbO₂ active coatings.With these electrodes as anodes, the electrocatalysis characteristics was researched for three different electrochemical processes,the oxygen evolution reaction in acidic media,the electrochemical oxidation of phenol and the electrochemical oxidation of Cr³⁺to Cr₂O₇^2-,respectively.The effects of the composition and preparation conditions of the coatings on the microstructure and surface morphology were investigated by XRD and SEM.Electrocatalytic activity of the coatings was characterized by cyclic voltammetry and active area of electrodes.The study of anode stability was performed under galvanostatic condition(4.0A·cm^-2or 2.0 A·cm^-2)at 60℃and 1.0 mol·L^-1in aqueous H₂SO₄.The PbO₂ coatings were prepared by three methods including thermal decomposition of Pb(NO₃)solution,anodic electrodeposition of Pb(NO₃)solution and electrochemical oxidation of Pb in H₂SO₄ solution.The three electrodes prepared by different methods have an even greater difference in the microstructure and surface morphology,which results in the difference in composition,oxygen evolution potential and electrochemical active surfaces.For the thermal decomposition method,Pb₃O₄ is obtained,which could be transformedβ-PbO₂ after undergoing electrochemical oxidation as an anode.The electrochemical active surface of the three electrodes lies in the order Ti/Sb-SnO₂/PbO₂ prepared by thermal decomposition＞Pb/PbO₂＞Ti/Sb-SnO₂/PbO₂ prepared by electrodeposition.The larger the electrochemical active surface is,the better the electrocatalytic performance is.A polymeric precursor method(PPM)is widely used to prepare nano-particles.The main advantages of preparing oxide particles by this method are low grain size and possibility of making low-level doped material.The PPM was hired to prepare the coatings of Sb-doped SnO₂ as the intermediate layers of Ti-based metal-oxide electrodes. The results show that the Sb-SnO₂ intermediate layers bright significant improvement in the electrochemical characteristics and the lifetime of the PbO₂ anodes.Comparing with other traditional precursor solvents(ethanol,n-butyl alcohol and ethylene glycol),the Sb-SnO₂ intermediate layers prepared by PPM assume high crystallinity and close microstructure,so the lifetime of the anodes with the Sb-SnO₂ intermediate layers prepared by PPM is enhanced.Three kinds of metal-oxide electrode,Ti/Sb-SnO₂/PbO₂,Ti/Sb-SnO₂/MnO_x and Ti/Sb-SnO₂,were prepared by thermal decomposition,in which Sb-dosed SnO₂ coatings were obtained by the polymeric precursor method.These electrodes were used as anodes in the process of electrochemical oxidation of phenol.The results show that the three kinds of electrode perform considerably difference.The best result is obtained with the Ti/Sb-SnO₂ anode,following by the Ti/Sb-SnO₂/PbO₂ anode and then the Ti/Sb-SnO₂/MnO_x anode, although complete phenol removal is achieved by all of the anodes.In the process of the electrochemical oxidation of Cr³⁺,Cr³⁺could be readily oxided at the Ti/Sb-SnO₂/PbO₂ anode;however,its oxidation is considerably slower at the Ti/Sb-SnO₂ anode and at the Ti/Sb-SnO₂/MnO_x anode without catalytic function.