Electron transfer reactions at surface films and passive layers

1 Electron transfer reactions at surface films and passive layers 

Several theoretical models have been developed in recent years to explain the experimental observations [102-106], The most important ETR mechanisms are as follows. 

Metal oxides which undergo proton insertion reactions find extensive application in batteries and are currently being investigated as potential electrochromic materials. The properties of battery oxides, e.g. manganese dioxide [107-110] and nickel [111-114] have been extensively reviewed in the literature and will therefore not be discussed here. Rather, the properties of electrochemically grown, electrochromic oxide films will be described since this is a relatively new and interesting field. 

Metal oxide films which change color in an electrolyte with change in applied potential [11, 115-123,127, 128, 137] have attracted a lot of attention in the past 15 years or so because of their potential application in electrochromic displays. Tungsten trioxide was the first oxide to receive significant attention in this regard [115-119] and, later, Ir oxide films [11, 120, 121, 127, 

128] proved more interesting from the viewpoint of fundamental electrochemical properties, e.g. potential-pH response, and will therefore be preferentially discussed here. 

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