Phase activity, binary transition metal

Trends in the electronic structure of the chalcogenide catalysts have proved to be helpful in the design and understanding of the catalyst clusters. During ORR, the molecular oxygen has been found to react with the cluster as a whole, rather than individual metal atoms.177 The overall number of electrons per cluster unit (NEC) in the valence bond has been shown to have a factor in the activity and stability of the cluster catalysts.177,181 The unsubstituted Chevrel phases have a NEC of 20.177,181 Substituting or intercalating other transition metals into the crystal lattice to make ternary or pseudo-binary Chevrel phases allows for the increase of NEC. It has been found that as the NEC approaches 24, the catalytic activity improves.181 Alonso-Vante compiled the results from his previous studies to show the effect of NEC in... 

Studies have also revealed that the implementation of nanostmctured electrode materials can result in the initiation of new lithium storage mechanisms. These effects typically manifest either via a pseudocapacitive storage mechanism that accommodates lithium ions on the surface/interface of the particles below a critical particle size or through a conversion mechanism that involves the formation and decomposition of at least two separate phases [28-31]. The pseudocapacitive mechanism is more pronounced because of the more prominent role of surfaces and grain interfaces in nanomaterials. Reversible conversion reactions based on the reduction and oxidation of metal nanoparticles can ensue between binary compounds comprised of some second or third period element, a transition metal oxide, and metaUic lithium [32-37]. Nanoparticles are extremely effective toward this means because of their large specific surface area that is very active toward the decomposition of the lithium binary compound. Furthermore, reduction of some micrometer sized materials to the nanoscale has been shown to activate or enable reversible electrode reactions that would otherwise not take place, typically materials with low Li-ion diflEiision coefficients. 

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