I've replicated a method I've found in a number of articles claiming to have produced a highly photocatalytic TiO2 thin coating but am not finding any success in degrading even low concentrations of Methylene Blue. Specifically, I'm adding TTIP (97% from Sigma Aldrich) dropwise under stirring at 500rpm and room temp into ethanol (bioethanol 99%). I have tried to reach the volume ratios described by others of 5mL TTIP to 50mL of Ethanol but find it quickly precipitates into large white particles and doesn't become transparent even after dropping the pH with HCl to 1.3. The maximum I could put in ending with a clear mostly sediment free solution is 1.3mL TTIP (into 50mL ethanol). From this transparent solution, I dip coated aluminium plates with a withdrawal speed of 1mm per second and calcined at 500°C for 1hr, then repeated the coating and calcining 6 times. I then put the aluminium plate in a quartz glass tube containing 50mL of Methylene Blue solution with an absorbance of 1.4 at 664nm and irradiated with an 11W UVA light under stirring. Spectrophotometer testing at 664nm showed no removal of Methylene Blue after a number of hours. Strangely, irradiating the solution with UVC 254nm light reduced the absorbance by 97% in 4 hours (just a reference check). I am out of funds but still have plenty of TTIP, HCl and ethanol as well as glacial Acetic Acid and ACAC (the last two chemicals not yet used). I also have Titanium Butoxide, HNO3 and 97% synthetic ethanol (in abundance). Does anyone have any suggestions of what I can do to make my coatings actually photocatalytic? What am I doing wrong? How can I maybe reach a molar ratio of 1:5 TTIP to Ethanol? Would this even help? Please help as I've run out of ideas.
You Must Change The Coating Technique That You Use Or Change Situations, Such As Roughness of Base Material or Coating Temperature.
Thank you for providing an answer however I wonder if you could please elaborate? Where do you see an issue with any of these techniques and in what specific way would you consider changing them?
Hi Dear Troy, Different Deposition Techniques Are Use, Such As: Sol-Gel, Thermal Treatment, Pulsed Laser Deposition, Reactive Evaporation, Physical Vapour Deposition (PVD), Chemical vapour deposition (CVD), Electrodeposition, sol-spray, Hydrothermal Deposition, etc. and About of Change of Situations: Rough Surfaces And Higher Temperature (Upper of 900°) Can Help to You For Best Results.
Thank you for your answer but i understand the many deposition routes and disagree that this could be the issue. Many success are reported viela the sol dip coating route. I have now tried quartz glass slides as a substrate with no improvement in my results. I do not agree that calcination at 900+ degrees will help as this will result in a phase change to rutile and it is important for me to remain in the anatase form for higher photocatalytic activity.
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