Technetium Encapsulation by A Nanoporous Complex Oxide 12CaO•7Al2O3 (C12A7)

Nitric Oxide Decomposition via Selective Catalytic Reduction by Ammonia on a Transition-Metal Cluster of W2TcO6

Decomposition of nitric oxide (NO) gas on a reactive transition-metal cluster of W₂TcO₆ has been examined and investigated via selective catalytic reduction by ammonia (NH₃-SCR) using the M06-L density functional method. The transition-metal cluster of W₂TcO₆ can be employed to transform NO to N₂ gas efficiently over an active site of tungsten (W). A reaction mechanism of NO conversion based on the NH₃-SCR process has been elucidated by a potential energy surface along the reaction pathways. The reaction pathways of this NH₃-SCR process begin with adsorption of NH₃, adsorption of NO to the cluster, formation of nitrosamine (NH₂NO) and NHNO/NHNOH intermediates, and rearrangement of NHNO/NHNOH to obtain N₂ and H₂O, respectively. Notably, a significant NH₂NO as a key intermediate, namely, "nitrosamine", must be formed before further steps can take place in the generation of N₂ from NO, followed by the involvement of the NHNO or NHNOH intermediate. From our calculated results, the NHNO intermediate via TS3a is found in pathway a, while NHNOH is found in pathway b via TS3b. Pathway b has a lower energy barrier of 35.1 kcal/mol than pathway a with an energy barrier of 41.8 kcal/mol, indicating that pathway b should be more energetically favorable. The step for NHNO intermediate rearrangement is a rate-determining step for the reaction occurring through pathway a, which is found to be more difficult in accordance with a difficult N-H bond cleavage to form the NNOH intermediate before N₂ formation. The overall reaction is an exothermic process with thermodynamic and kinetic favors. Thus, this bimetallic W₂TcO₆ cluster could be used as a promising and active catalyst for NO decomposition via the NH₃-SCR process to an eco-friendly gas, that is, N₂.

Lithium Storage in Nanoporous Complex Oxide 12CaO•7Al2O3 (C12A7)

Porous materials have generated a great deal of interest for use in energy storage technologies, as their architectures have high surface areas due to their porous nature. They are promising candidates for use in many fields such as gas storage, metal storage, gas separation, sensing and magnetism. Novel porous materials which are non-toxic, cheap and have high storage capacities are actively considered for the storage of Li ions in Li-ion batteries. In this study, we employed density functional theory simulations to examine the encapsulation of lithium in both stoichiometric and electride forms of C12A7. This study shows that in both forms of C12A7, Li atoms are thermodynamically stable when compared with isolated gas-phase atoms. Lithium encapsulation through the stoichiometric form (C12A7:O2−) turns its insulating nature metallic and introduces Li+ ions in the lattice. The resulting compound may be of interest as an electrode material for use in Li-ion batteries, as it possesses a metallic character and consists of Li+ ions. The electride form (C12A7:e−) retains its metallic character upon encapsulation, but the concentration of electrons increases in the lattice along with the formation of Li+ ions. The promising features of this material can be tested by performing intercalation experiments in order to determine its applicability in Li-ion batteries.