Graphyne and Graphdiyne: Promising Materials for Nanoelectronics and Energy Storage Applications

Ab initio first-principles calculations were carried out to investigate lithium-dispersed two-dimensional carbon allotropes, viz. graphyne and graphdiyne, for their applications as lithium storage and hydrogen storage materials. The lithiation potentials (vs Li/Li+) and specific capacities in these materials are found to be enhanced considerably as compared to the conventional graphite-based electrode materials. Lithium metal binding to these carbon materials is found to be enhanced considerably and is more than the cohesive energy of lithium. Each lithium atom in these metal-dispersed materials is found to carry nearly one unit positive charge and bind molecular hydrogen with considerably improved adsorption energies. Our calculated hydrogen adsorption enthalpies (-3.5 to -2.8 kcal/mol) are very close to the optimum adsorption enthalpy proposed for ambient temperature hydrogen storage (-3.6 kcal/mol). We have also shown that the band gaps in these planar carbon allotropes can be tuned by varying the number of acetylenic bridging units which will have versatile applications in nanoelectronics.