Study of the structural evolution of copper-doped porous silica gels Original Research Article

Porous silica gels have been prepared by the sol–gel method using tetraethoxysilane (TEOS), ethanol and water with two dopants, CuCl and CuSO4, with different copper contents (1 and 5 mol%). The samples were prepared as monolithic shapes, dried at 110°C for 24 h and heat treated at 500, 900 and 1100°C. Their structural evolution was studied by gas absorption, X-ray diffraction and X-ray absorption spectroscopy. All samples showed a stable structure of pores up to 900°C and a strong densification process at 1100°C. For temperatures lower than 500°C, an amorphous material was formed, and the crystalline phases of cristobalite, quartz, cuprite and tenorite were determined after heat treatment at 900°C. CuO was formed in the pores of samples doped with CuCl heated at 900 and 1100°C. In the pores of samples doped with CuSO4, CuO was formed at 900°C and Cu2O at 1100°C.