Electrochromism of anodic oxide film on TiN coating in aqueous and non-aqueous electrolytes

Electrochromism of an anodic oxide film formed on a TIN coating was investigated in both a neutral berate buffer aqueous solution and a propylene carbonate solution containing LiClO4. The TiN coating was prepared on Pt or stainless steel substrates, and was oxidized by anodic polarization in aqueous solution. The color of the TiN surface changed from gold to black when H+ or Li+ was absorbed into the oxide layer during cathodic polarization, and it turned to gold when H+ or Li+ was released during anodic polarization. Spectroscopic reflectance measurements showed that Light absorption occurs in the whole visible range during coloring. In the aqueous solution, the time responses of coloring and bleaching processes were shorter than 1 s in the case of a fresh oxide layer. When the coloring/bleaching cycle was repeated over a long period, the response was delayed due to oxide layer thickening. AFM observation showed that the coloring/bleaching cycling was accompanied by the surface roughening, which would decrease the lifetime of TiN as an electrochromic device in an aqueous solution. In the non-aqueous solution, the time response of coloring and bleaching was slow, suggesting that the accumulation of Li in the oxide layer degrades the electrochromic property considerably. (C) 1999 Elsevier Science S.A. All rights reserved.