Peroxo sol-gel preparation: photochromic/electrochromic properties of Mo-Ti oxide gels and thin films

Metallic Mo powder and Ti(OBun)(4) were separately dissolved in H2O2 solution and the solutions obtained mixed in different Mo/Ti atomic ratios to prepare precursor solutions. Fresh gels obtained from the precursor solutions with > 40% Mo became blue upon exposure to ambient light. X-Ray photoelectron spectroscopy (XPS) was used to examine the chemical states and compositions of the resultant blue-tinged xerogel powders. Based on the XPS results, it is proposed that TiO2 particles and surface species, including adsorbed water and organic residue, all contribute to the photochromic effect of MoO3. Mo-Ti oxide films were spin-coated on ITO-coated glass substrates using a precursor solution containing 70% Mo. The cycling behaviours of the films annealed at 150 degrees C for 1 h were studied using cyclic voltammetry (CV) in propylene carbonate solution containing 1 mol L-1 LiClO4. The electrochromic properties of the films upon lithium intercalation were investigated by in situ monochromatic transmittance measurements during the CV process, as well as ex situ in the UV/Vis region. The Mo-Ti oxide films were found to possess excellent electrochromic properties upon Li+ ion insertion/extraction.