The practical electroactivity of electrically insulating iron fluoride was enabled through the use of carbon-metal fluoride nanocomposites ͑CMFNCs͒. The nanocomposites were fabricated through the use of high energy mechanical milling and resulted in nanodomains of FeF 3 on the order of 1-20 nm encompassed in a matrix of carbon as characterized by transmission electron microscopy and X-ray diffraction ͑XRD͒. Electrochemical characterization of CMFNCs composed of 85/15 wt % FeF 3 /C resulted in a nanocomposite specific capacity as high as 200 mAh/g ͑235 mAh/͑g of FeF 3 ) with the electrochemical activity associated with the Fe 3ϩ → Fe 2ϩ occurring in the region of 2.8-3.5 V. The CMFNCs revealed encouraging rate capability and cycle life with Ͻ10% fade after 50 cycles. Structural evolution during the first lithiation reaction was investigated with the use of ex situ and in situ XRD. Initial results suggest that x from 0 to 0.5 in Li x FeF 3 proceeds in a two-phase reaction resulting in a phase with significant redistribution of the Fe atoms within a structure very similar to the base FeF 3 . FeF 3 -based CMFNCs also exhibited a very high specific capacity of 600 mAh/g at 70°C due to a reversible reaction at approximately 2 V.

The structure and electrochemistry of FeF 3 :C-based carbon metal fluoride nanocomposites ͑CMFNCs͒ was investigated in detail from 4.5 to 1.5 V, revealing a reversible metal fluoride conversion process. These are the first reported examples of a high-capacity reversible conversion process for positive electrodes. A reversible specific capacity of approximately 600 mAh/g of CMFNCs was realized at 70°C. Approximately one-third of the capacity evolved in a reaction between 3.5 and 2.8 V related to the cathodic reduction reaction of Fe 3ϩ to Fe 2ϩ . The remainder of the specific capacity occurred in a two-phase conversion reaction at 2 V resulting in the formation of a finer Fe:LiF nanocomposite. Upon oxidation, selective area electron diffraction characterization revealed the reformation of a metal fluoride. Evidence presented suggested that the metal fluoride is related to FeF 2 in structure. A pseudocapacitive reaction is proposed as a possible mechanism for the subsequent Fe 2ϩ → Fe 3ϩ oxidation reaction. Preliminary results of FeF 2 , NiF 2 , and CoF 2 CMFNCs were used in the discussion of the electrochemical properties of the reconverted metal fluoride.

Near-theoretical utilization of high-energy-density CuF 2 positive electrode materials for lithium batteries was enabled through the use of nanocomposites consisting of 2-30 nm domains of CuF 2 within a mixed ionic + electronic conducting matrix of a metal oxide. Small but significant crystallographic changes to the core crystal of the CuF 2 were found to occur in all oxide-based matrices. These modifications to the core crystal and the surrounding matrix were investigated through a host of characterization methods, including XRD, XPS, and XAS. This new approach to the enablement of the anhydrous CuF 2 is distinctly superior in performance to that of macro CuF 2 or CuF 2 nanocomposites utilizing carbon as a matrix, the latter of which is also introduced herein for the first time.

We survey recent studies and present new data on the growth, interactions, structure and chemistry of gold deposited on TiO 2(110) surfaces. The noble metal Au on TiO 2(110) is a model system for weak interaction of a metal with an oxide substrate; it is also of interest because Au on TiO 2 has unusually high activity as a catalyst for CO oxidation at room temperature. In this review, we present results on the growth of ultrathin films of Au on TiO 2(110), as well as the morphology, interface formation, epitaxy, structure and electronic properties of Au on TiO 2 single crystal and planar films. The results are compared to studies of Au on high-surface-area TiO 2 catalysts in an attempt to bridge the gap between surface science experiments and the high pressure conditions of catalyst operation.