Preparation of cerium-doped titania macroporous films by a sol–gel spin coating using polypropylene glycol (PPG) as pore-creating agent: Effects of Ce ions, PPG and calcination on photocatalytic activity

Cerium-doped titania macroporous films (CTMs) were spin-coated on glass substrates from a controlled sol–gel solution using titanium alkoxide and polypropylene glycol (PPG) as precursor and pore-creating agent, respectively. The physicochemical properties of CTMs were characterized by scanning electron microscope (SEM), thermogravimetric and differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD) and BET surface area analysis. The photocatalytic activity of CTMs was evaluated by degradation of methylene blue (MB). The results showed the decomposition of PPG during calcinations was responsible for the generation of macroporous structure in the films. The Ce ions, PPG and calcination respectively influenced recombination of electron–hole pairs, surface area, hydroxyl concentration and crystalline structure of films, so that one of those factors could restrict the photocatalytic activity of films. Compared with others films, CTMs-1 showed the highest photocatalytic activity with 0.5 wt.% of Ce doping concentration and 2.0 g PPG additions at calcinating temperature of 550 °C. It was mainly attributed to the effects that both the optimum concentration of Ce ions doping and high surface area could promote the photocatalytic degradation by preventing recombination of electron–hole pairs and providing more MB molecules around TiO2 and high concentration of hydroxyl.