During our development of our final idea, our group reached three other potential ideas that would work, just not as efficiently.

The first idea was using thermo-energy to heat up TiO₂, allowing electrons to cross band gaps.  However, these temperatures would have to be very high to reduce the energy needed to that which is obtainable from visible light.  It would require a lot of energy as well, making the technology quite expensive and inefficient.

The second idea was to use other semiconductors to act as catalysts.  These included iron oxides, such as Fe₂O₃, with an E_g of 2.2 eV, and metal sulfides, such as CdS, which has an E_g o f2.5 eV.  However, these semiconductors may be unstable and vulnerable to corrosion.

The final choice was to use electron beams to bombard TiO₂ to move electrons from the valence band to the conduction band.  However, this is too expensive and requires a lot of modern high-tech equipment.  Furthermore, it would be difficult to implement in everyday on-site solutions, a very impractical choice.