Development of thin-film nickel hydroxide electrochromic materials using in situ microfocus XAFS and XRD techniques

The use of nickel hydroxide as a colour switching material in electrochromic devices such as smart windows is yet to be fully exploited. Stabilisation of the highly electroactive α nickel hydroxide / γ nickel oxyhydroxide redox couple through co-deposition of other metal ions could lead to devices with improved performance in terms of response time and cycle lifetime. This thesis presents the current understanding of nickel hydroxide phases and their relationship to one another, various ways to form nickel hydroxide materials and the effect of doping nickel hydroxide materials with cobalt, cadmium, zinc, manganese, iron, aluminium ions. In addition, this thesis describes the basic components of an in situ electrochemical cell and compares in situ cell designs used to study electrochemically active thin films under potential control with synchrotron light sources. The thesis follows with a description of the synthesis of various phases of nickel hydroxide via chemical precipitation to form powder and the electrochemical deposition method to deposit thin films and demonstrates the development of a novel in situ electrochemical flow cell, designed for in situ XAFS analysis of nickel hydroxide thin films under potential control. The thesis also highlights that this is the first time a transparent conductive oxide coated polymer film is used as both a working electrode and x-ray window material for an in situ electrochemical cell.