Theoretical Calculation And Phase Diagram Of Titanium Oxide Anode Solid Solution

Titanium anodes in electrochemical industry, such as electrochemical synthesis and the degradation of pollutant, is very promising. However, the formation of insulator can cause a reduction of conductivity and binding force, especially in a strong acid. The oxides intermediate layer can improve corrosion resistance, binding force and conductivity. Mn and Sb doped SnO2 solid solution among the intermediate layers can enhance the stability and conductivity of electrodes. However, the formation and effects mechanism of solid solution on the performance of electrode has been rarely studied, so the theory has lagged behind and hindered titanium anodes further development.The SnO2-SbOx-MnO2 ternary system was studied and discussed by the method of experiment,theory and calculation in this paper:(1) the (MnOa) x-(SbOb)0.05-SnO2 and (MnOa)x-(SbOb) 0.15-SnO2 solid solution were prepared using the chemical precipitation method in 600℃～1000℃annealing temperatures; (2) the SnO2-Sb2O3-MnO2 ternary system solid solution was prepared by the chemical precipitation method in 1000℃annealing temperatures; (3) the formation energy and the electronic structures on Sn1-xPbxO2 and Sn0.5Mn0.5 O2 solid solution were calculated by the first principles method based on density functional theory. Results show that:1. In the phase diagram of Sn1-x-yMnxSbyO2 (y=0.05), SnO2 was existed in rutile type single-phase area when x value is 0 to 0.3, Sb and Mn were mainly in the form of Sb5+,Mn3+ and Mn4+ entering the SnO2 lattice to form a limited solid solution; the phase diagram of Sn1-x-yMnxSbyO2 (y=0.15) is divided into five areas, including two single-phase area of tetragonal phase SnO2 and (Sn,Sb) O2ss solid solution.2. The phase relationship of SnO2-Sb2O3-MnO2 ternary system contained two single-phase areas, eight two-phase areas and three three-phase areas. One of the single-phase area was mainly the rutile SnO2, the other single-phase area was mainly the (Sn, Sb)O2ss. The oxides in these two areas can serve as a good conductivity and corrosion resistance of intermediate anode materials.3. After Pb substituted the Sn of SnO2, the crystal lattice constant was increased, while doping formation energy also changed with doping ratio. The Sn0.9375Pb0.062502 solid solution has the highest stability because it has a minimum value of 0.04589eV at the doping ratio of 0.0625. there is Pb 6s distribution of electronic states from Fermi lever to the bottom of conduction band after Pb doped.4. The lattice constant and cell volume of Sn0.5Mn0.5O2 unit cell are between SnO2 and MnO2 unit cell. The cohesive energies of SnO,MnO2 and Sn0.5Mn0.5O2 are -2.4eV,-10.5eV and -4.5eV respectively, this suggests that MnO2 has the highest stability. The calculation shows that Mn 3d distribution of electronic states exists from the Fermi level to the lowest conduction band after Mn doped SnO2, band gap of SnO2 was reduced after Mn doped. Therefore, Sn0.5Mn0.5O2 solid solution had a strong conductivity.