Multiphase Gibbs ensemble Monte Carlo simulations were carried out to compute the free energy of swelling for Na-montmorillonite and Na-beidellite interacting with CO 2 and H 2 O at pressure and temperature conditions relevant for geological storage aquifers. The calculated swelling free energy curves show stable monolayer and bilayer configurations of the interlayer species for Namontmorillonite, while only the monolayer structure is found to be stable for Na-beidellite. The calculations show that CO 2 is intercalated into hydrated clay phases at concentrations greatly exceeding its solubility in bulk water. This suggests that expandable clay minerals are good candidates for storing carbon dioxide in interlayer regions. For Na-beidellite the CO 2 molecule distribution is mainly controlled by the position of the isomorphic substitutions, while for Namontmorillonite the presence of the hydrated sodium ions plays an important role in establishing the CO 2 distribution.

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Titanium dioxide is the only known material that can enable gas-phase CO 2 photocatalysis in its anatase and rutile polymorphic forms. Materials engineering of polymorphism provides a useful strategy for optimizing the performance metrics of a photocatalyst. In this paper, it is shown that the less well known rhombohedral polymorph of indium sesquioxide, like its well-documented cubic polymorph, is a CO 2 hydrogenation photocatalyst for the production of CH 3 OH and CO. Significantly, the rhombohedral polymorph exhibits higher activity, superior stability and improved selectivity towards CH 3 OH over CO. These gains in catalyst performance originate in the enhanced acidity and basicity of surface frustrated Lewis pairs in the rhombohedral form.

Two-dimensional polyaniline with a C 3 N stoichiometry, is a newly fabricated material that has expected to possess fascinating electronic, thermal, mechanical and chemical properties . The possibility of further tuning the C 3 N properties upon the adsorption of foreign adatoms is thus among the most attractive researches. We carried out extensive ab-initio density functional theory (DFT) simulations to investigate the adsorption of various elements including nonmetallic, metalloidic and metallic elements on the C 3 N monolayer. While pristine C 3 N acts as a semiconductor with an indirect electronic band gap; the functionalization with nonmetallic and semimetallic elements leads to a p-type doping and induces metallic behavior to the monolayer.On the other hand, metallic adsorption depending on the adatom size and the number of valence electrons may result in semiconducting, half-metallic or metallic properties. Whenever metallic foreign atoms conduct metallic characteristics, they mostly lead to the n-type doping by electron donation to the surface. Moreover, adsorption of transition metals could enhance the magnetic behavior of the monolayer due to the contribution of d electronic states. These results suggest that C 3 N illustrates viable electronic-magnetic properties which could be promising for semiconducting, nanosensores and catalytic applications.2

Two-dimensional allotropes of group-IV substrates including silicene, germanene and stanene have recently attracted considerable attention in nanodevice fabrication industry. These materials involving the buckled structure have been experimentally fabricated lately. In this study, first-principles density functional theory calculations were utilized to investigate the mechanical properties of single-layer and freestanding silicene, germanene and stanene. Uniaxial tensile and compressive simulations were carried out to probe and compare stress-strain properties; such as the Young's modulus, Poisson's ratio and ultimate strength. We evaluated the chirality effect on the mechanical response and bond structure of the 2D substrates.Our first-principles simulations suggest that in all studied samples application of uniaxial loading can alter the electronic nature of the buckled structures into the metallic character. Our investigation provides a general but also useful viewpoint with respect to the mechanical properties of silicene, germanene and stanene.