Not Sure how TiO2 would work. You still need source of carbon. Estimate your budget first. If you want to make it affordable - you need either burn something to produce CO2 or use a compressed (liquid) CO2 in tanks. If you have source of power (plug) you can theoretically extract CO2 from air - but this is quite bulky and expensive.
Also, I do not know your design and purpose of using CO2, but you can try to run your experiment with compressed CO2. If it generally works, try to implement different techniques of producing CO2.