In this work, using density functional theory, a twin-graphene-based anode material is investigated for the use in rechargeable ion batteries with sodium as the intercalating ion. The pristine twin-graphene structure yielded two best adsorption sites of its surface where the Na atoms are adsorbed in a layer-wise fashion. We report a theoretical capacitance of 496.2 mAh/g for Na-adsorbed twin-graphene, which is significantly higher than those of many other carbon allotropies. From NEB calculations, a low diffusion barrier in twin-graphene suggests good diffusivity, and with a moderate value of open-circuit voltage, twin-graphene is a good choice for applications as an anode material in Na-ion rechargeable batteries.

In this study, a magnesium ion rechargeable battery with twin‐graphene based anode material has been proposed and studied for its feasibility as a suitable option to replace the commercially available lithium‐ion rechargeable batteries. The adsorption of magnesium ion is tested at different sites on the substrate and adsorption at the trigonal sites is seen to be the most stable one. A 2×2×1 supercell of twin‐graphene is seen to accommodate a maximum of 8 Mg ions which gives a high theoretical capacitance of 496.2mAh/g. The Mg adsorbed anode material is seen to be thermodynamically stable in both single and fully accommodated systems. Nudged elastic band (NEB) calculations for the movement of Mg ions via different paths reveal a low diffusion barrier for the movement of ions which is indicative of higher diffusivity in the system and faster charging rates which render twin‐graphene as a suitable material for use in Mg‐ion batteries (MIB).

‘Twin-graphene’ bilayer based nanoscale capacitor and nanoscale dielectric capacitor are designed using density functional theory approach including van der Waals dispersion correction. A strong effect on electronic properties is observed...

A detailed density functional theory investigation of He 2-encapsulated fullerene C 36 and C 40 has been presented here. When confinement takes place, He-He bond length shortens and a non-covalent type of interaction exists between two He atoms. Energy decomposition analysis shows that though an attractive interaction exists in free He 2 , when it is confined inside the fullerenes, repulsive interaction is observed due to the presence of dominant repulsive energy term. Fullerene C 40 , with greater size, makes the incorporation of He 2 much easier than C 36 as confirmed from the study of boundary crossing barrier. In addition, we have studied the possibility of using He 2-incorporated fullerene as acceptor material in dye-sensitized solar cell (DSSC). Based on the highest energy gap, He 2 @C 40 and bare C 40 fullerenes are chosen for this purpose. Dye constructed with He 2 @C 40 as an acceptor has the highest light-harvesting efficiency and correspondingly will possess the maximum short circuit current as compared to pure C 40 acceptor.

In this study, thirteen donors with the same spacer and acceptor have been tested to model dyes for dye sensitized solar cell (DSSC). Amongst the thirteen donors, 7,7,13,13-tetramethyl-8,9,12,13-tetrahydro-2H,5H,7H,11Hpyrano[2′,3′:4,5]pyrano[2,3-f]pyrido[3,2,1-ij]quinoline-2,5-dione is found to possess the highest oscillator strength amongst the other dyes in first excited state. This donor has been studied further with five different acceptors, among which, the dye with rhodanine acetic acid acceptor as well as its conformer have the lowest HOMO-LUMO energy gap (Eg), highest absorption wavelength in the UV-visible spectrum with high oscillator strength and low exciton binding energy in the first excited state as compared to the other four dyes considered here. The rhodanine acetic acid based dyes have shown to outperform all the other four dyes in terms of chemical reactivity parameters. All the six dyes when tested further with the inclusion of an extra benzene spacer show enhanced overall performance, with the rhodanine acetic acid based dyes showing the most planarity, highest absorption wavelength, more suitable reactivity parameters etc. Correlation studies between the solar cell parameters and chemical reactivity parameters have also been conducted where a direct relationship between the chemical hardness of the dye and open circuit voltage has been observed.

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