The main question here is, "What do you want to catalyze in this reaction?". Also, how do you plan on testing to determine if any reaction is taking place? On a low budget, I would suggest a dye that would react with your product at extremely low levels to show a color change of the solution. Mix the TiO2 with water, add your species you wish to catalyze, and introduce a light source. You will need some way to stir the mixture as titanium dioxide does not dissolve in water, and will settle out of the mixture. Also, from my experience with this material, oxygen is pretty important in the reaction so you need to have some way of bubbling air or pure oxygen into the mix (fish tank pump would work). Then you want to take samples at specific time increments and filter these samples to remove all of the catalyst. That is where is gets difficult as the syringe filters are pretty expensive. Than add the dye to the samples you have collected and see if there is any color change over an extended period of time. The best case would be that a noticeable change has occurred, the worst case would be that you predicted the wrong product and need to try a different dye. As far as materials go, all of this can be done in a mason jar in direct sunlight with a couple of syringes and filters. The difficulty is determining rate of reaction and what the hell the products are without a GC or HPLC.