There are various methods available to coat TiO2 onto the surface of the membrane. I will explain briefly some of them, and the method I used.
Ion assisted deposition
This method was used for coating on super-hydrophobic porous teflon membrane. The author stated that the coating of TiO2 by the chemical wet process such as a sol-gel method is very difficult. The method involved acceleration voltage, temperature, and oxygen. Heated at 523 K.