We report on a new class of core-shell electrocatalysts for the oxygen-reduction reaction. These electrocatalysts comprise a Pt monolayer shell and ordered intermetallic compounds cores and have enhanced activity and stability compared with conventional ones. These advantages are derived from combining the unique properties of Pt monolayer catalysts (high activity, low metal content) and of the intermetallic compounds (high stability and, possibly, low price). This method holds excellent potential for creating efficient fuel cell electrocatalysts.

Nanomaterials as catalysts for fuel cells are not only highly desirable, but necessary to reach the high reaction rates (or power densities) demanded by many applications. The exploration of catalyst materials beyond Pt metal, such as Pt containing alloys and intermetallics, immediately leads to significant synthetic challenges to prepare nanoparticles with controlled composition, structure, and morphology. To facilitate a comprehensive study of these materials, a generalized synthetic approach is desirable. This requires an in-depth understanding and control of relevant factors that thermodynamically and kinetically define the synthesis process. Once synthesized, electrochemical activities of these materials can then be studied to aid in designing the next steps in further optimizing the catalyst activity. In this work, we have been able to demonstrate synthesis of several phases (both alloy and ordered intermetallics for binary Pt−V/Mn/Cr/Ni/Cu systems) that rarely, if ever, have been synthesized as nanomaterials without using surfactants. Additionally, we have shown that some of these materials are active catalysts, with activity superior to Pt for formic acid oxidation. Finally, we have established general guidelines and methodologies for synthesis of alloy and intermetallic phases as nanomaterials with highly reactive metals like Cr, V, and Mn.

An "all-inorganic", fast, and power-efficient solid-state electrochromic device has been realized by choosing Co 3 O 4 and PB films as complementing electrodes. The prussian blue and cobalt oxide films have been synthesized via a simple galvanostatic method to achieve better film quality to be used in a device. Prior to fabricating a prototype solid-state device, the electrodes have been tested using in situ electrochemical and spectroscopic studies. This is followed by fabricating a solid-state device that shows switching between multiple colors with an applied bias of less than a couple of volts. A moderate color contrast of ∼40% with 1.5 s switching time has been observed with showing stability for more than 900 s of continuous switching. A redoxdriven electrochromic behavior of individual electrodes makes it possible for the solidstate device to show beautiful colors with a small applied bias. Electrochemical and spectroscopic measurements have been carried out to establish the possible mechanism of color switching shown by the device. Moreover, a coloration efficiency of ∼250 cm 2 /C makes it comparable to an "all-organic" or hybrid solid-state device, with its strong nature being an additional advantage.

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