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 investi gated in both a neutral berate buffer aqueous solution and a propylene carb onate solution containing LiClO4. The TiN coating was prepared on Pt or sta inless steel substrates, and was oxidized by anodic polarization in aqueous solution. The color of the TiN surface changed from gold to black when Hor Li+ was absorbed into the oxide layer during cathodic polarization, and it turned to gold when H+ or Li+ was released during anodic polarization. S pectroscopic reflectance measurements showed that Light absorption occurs i n the whole visible range during coloring. In the aqueous solution, the tim e responses of coloring and bleaching processes were shorter than 1 s in th e case of a fresh oxide layer. When the coloring/bleaching cycle was repeat ed over a long period, the response was delayed due to oxide layer thickeni ng. AFM observation showed that the coloring/bleaching cycling was accompan ied by the surface roughening, which would decrease the lifetime of TiN as an electrochromic device in an aqueous solution. In the non-aqueous solutio n, the time response of coloring and bleaching was slow, suggesting that th e accumulation of Li in the oxide layer degrades the electrochromic propert y considerably. (C) 1999 Elsevier Science S.A. All rights reserved.