Ab Initio Study on the Potential of Metal-Decorated Pristine and Activated Carbyne for Hydrogen Storage Applications

One-dimensional (1D) materials are potential hydrogen storage candidates due to their low density, large surface area, and high structural stability. Taking into consideration a study reported in the literature about an activated carbyne C12-ring with zinc dichloride (ZnCl2), this work was set to investigate the maximum hydrogen storage capacity of pristine and metal-functionalized carbyne, comprehensively studying different interactions: alkali-metal (AM = Li, Na, K), alkaline-earth metal (AEM = Be, Mg, Sr, Ba), and transition-metal (TM = Sc, Ti, V, Ni, Y) with molecular hydrogen via density functional theory with vdW corrections. The results exhibited that chemical activation of the C12-ring with ZnCl2 increased the binding energy of MC12 by ∼20–50% for carbyne functionalized with alkali metals, ∼16–30% for alkaline-earth metals, and ∼10–25% for transition metals with respect to the pristine carbyne, thus preventing clustering of metal atoms. It was found that M = Li, Sr, Sc, Ni, and Y materials displayed a moderate adsorption energy within the 0.2–0.6 eV range and were suitable for hydrogen adsorption under near-ambient conditions. In addition, LiC12-5H2, SrC12-7H2, ScC12-6H2, NiC12-6H2, and YC12-7H2 single-decoration atom systems reached up to 6.25, 5.73, 6.01, 5.62, and 5.70 wt % hydrogen gravimetric density, respectively, thus meeting the U.S. Department of Energy (DOE) ultimate target by the 2025 year. Therefore, an activated carbyne complex can bind a maximum of 3 decorating atoms with the same number of hydrogen molecules, therefore reaching a high gravimetric density (HGD) from 9 to 15 wt %. Thermal stability and desorption temperatures of M3C12-nH2 (M = Li, Sr, Sc, Ni, Y) structures were determined via molecular dynamics simulations and using the van't Hoff equation, showing that hydrogen molecules were easy to desorb at room temperature (T = 300 K). According to the obtained results, the activated carbyne C12-ring was highlighted as a potential candidate for hydrogen storage material for fuel cell applications.