The gas phase mechanism process of TiCl4 oxidation to rutile TiO2 and the inhibition of KCl on crystal nucleation

This paper studied the microscopic mechanism of the gas phase nucleation reaction during the TiCl4 oxidation-reduction reaction and the inhibition effect of the nucleation inhibitor KCl on TiO2 nucleation. The optimal pathway for TiO2 nucleation was identified as TiCl3 + Ti2O2Cl5 -> TiCl4 + Ti2O2Cl4, achieved through calculation and optimization of the transition state, coupled with an analysis of the reaction energy barriers and their respective pathways. The cluster structure model of (TiO2)(n) (where n = 1 similar to 7) and its stable configuration were optimized. For clusters where n = 1-2, the B3LYP functional provides a more accurate calculation of the excited state energy. Conversely, the PW91 functional demonstrates higher accuracy for larger clusters, indicative of a stronger coupling effect between the electronic state and atomic nucleus vibration in the system. Comparing the change trend of the bond length of O-2c,O- O-3c and Ti-5c, shows that the optimal site of K+ adsorption on the rutile TiO2 (110) surface is O-2c. Based on this, the adsorption mechanism of TiCl4 molecules on a complete rutile type TiO2 (110) surface containing one oxygen defect and two oxygen defects was studied. The results shows the adsorption energy increases, and the adsorption structure is unstable with oxygen defects.