Facile low-temperature synthesis of nickel oxide by an internal combustion reaction for applications in electrochromic devices

Electrochromic nickel oxide ion storage anodes compatible to tungsten oxide as cathode layer are prepared by a combustion reaction with urea as fuel and nickel nitrate as oxidizer at temperatures not higher than 230 degrees C to stay well within the temperature range in which thermally sensitive intercalated tungsten oxide layers are still stable. The precursors for nickel oxide are well available materials and the preparation of the layers can be performed at low energy input by spin-coating onto the substrate and moderate heating on a hot-plate. Ethanol and acetone where used as solvents and reveal large differences in the resulting film morphologies, electric and electrochromic characteristics. Cyclic voltammetry measurements in contact to lithium perchlorate (LiClO4) in propylene carbonate show remarkable colouration efficiencies at 550 nm of 47 cm(2) C-1 for NiO prepared from ethanol solution and 92 cm(2) C-1 for NiO prepared from acetone solution, which are, to the best of our knowledge, among the highest reported values for L+-tintercalation into NiO prepared at moderate substrate temperature reported so far. [GRAPHICS] .