Research On The Application Of TiO₂ To Cathode Catalyst Of Zinc-air Battery And Photocatalyst

Nanophase materials have become an important study focus with the fast development of nanophase science and technology. TiO₂ with size between 1nm and 100nm has specific performances such as surface effect, eimensional effect and optical performance. Therefore, the applied studies of TiO₂ have prodigious and latent importance for future study. The application of TiO₂ to cathode catalyst of zinc-air battery and photocatalyst were researched in the present study. TiO₂/AC powder which was equal distribution of load was prepared by TiCl₄ one-step vapor-hydrolysis method. Two maximal merits of this method were equal distribution of load and good for preventing conglobation of nanometer particle in calcining process. The primary tasks in this paper include preparation of catalysis and air electrode, study on discharge performance of air battery, electrophoretic deposition of TiO₂ and measurement of photocatalytic performance of TiO₂. The catalysis operation for O₂-deoxidation and influence factors of photo-catalytic performance were discussed.The size, phase and surface bonding condition of the particles and the performances of the semiconductor electrodes were investigated by different material characterization methods and electrochemical techniques such as XRD, linear polarization and electrochemical impedance spectroscopy. The properties, the composition proportions and processing parameters were optimized. The performances of electrodes were studied by polarization curve method and discharging curve test. In addition, the photocatalytic performance of the powder and the film were studied by means of photocatalytic degradation of phenol in water.The XRD and FTIR spectra of TiO₂/AC powder showed that anatase titanium dioxide in the size of 16.5 nm was produced after calcining at 400℃and the Ti—O—C bondings which combined firmly appeared on the surface between TiO₂ and AC. The effects of preparation conditions, such as the compositions of catalyst layer and hydrophobic layer, preprocess of AC, temperature of crystal conversion, confection pressure and calcination temperature on the performance of gas diffusion electrode were studied by using linear polarization technique when the catalysis was TiO₂/AC. The experimental results showed that the performance of gas diffusion electrode greatly depended on its composition and preparation conditions, and the electrodes with better performance could be obtained under the following preparation conditions.Composition of electrodes: 100 mesh coprum net is used as electric conductor. Composition proportions are as follows: 5mL PTFE, 10mL TiCl₄, 3mL PEG600, 11-13mL AEG and 0.8mg acetylene black.Processing parameters: anatase titanium dioxide was produced after calcining at 400℃, three parts of the electrode was pressed together at 25MPa for 30-60s, the confectioning electrode was calcined at 340℃for 30min and was steeped in acetone for 13h to eliminate the effect of PTFE so as to form the tightly packed network state structure with very small space in the electrode, and to increase the performance of drainaging and ventilation; when the thickness of electrode is 0.53nm, the performance of electrode was better; AC which was preprocessed in nitric solution (10wt%) to eliminate additive and ashes was sieved for 300 mesh could make the performance of electrode better.Performances test: the EIS spectra showed that the TiO₂/AC powder had catalysis operation for O₂ deoxidation, the procedures of O₂ diffusion and mass transport of reaction particle on the three-phase boundary might be a slow procedure. When the current density of the air-electrodes reached 150 mA/cm², the terminal voltage of the air-battery would maintain above 0.8V. The discharging performance was stable and the discharging time is very long.The photocatalysis degradation performance of TiO₂/AC powder in suspending liquid system was studied when phenol was the aim pollutant. The experimental results showed that the adsorption equilibrium time was about 30min and the TiO₂/AC powder with better photocatalysis performance could be obtained under the following conditions: the content of TiO₂ was about 95%; the initial phenol concentration was about 10mg/L; the dosage of TiO₂/AC powder was about lmg/mL; the initial concentration of H₂O₂ was about 50mg/L; when the pH was about 5, the photocatalysis performance was better. The degradation ratio was high in the wide range of pH under the same conditions.When the dispersive medium was organic phase (isoproanol), TiO₂ film was prepared on the surface of air-electrode by electrophoresis method. It could actualize the immobilization of photocatalyst. By this method, the photo-anode was prepared and the problem of solid-to-liquid separation in suspending liquid photocatalysis system was solved. By inputting applied pressure, the electrons flow to cathode through external circuit and the electron holes transfer to surface of catalyst. Under this good condition of charge separation, the simple recombination probability of electron-hole was reduced greatly and the degradation efficiency of phenol was increased greatly. The experimental results showed that the prerequisite of preparing high performance film was appropriate electric-field intensity. The time of adsorption equilibrium was about 30min and the TiO₂/air-electrode with better photocatalysis performance could be obtained under the following conditions: the electrophoresis voltage was about 30V and the electrophoresis time was about 5min; the applied pressure was 0.25V; the initial concentration of H₂O₂ was about 50～100mg/L; when the pH was about 5, the photocatalysis performance was better and the degradation ratio was difficult to maintain high photocatalysis performance in the wide range of pH under the same conditions; the useful life period of TiO₂/air-electrode was short contrasting with TiO₂/AC powder.