Tailored Metal-Doped Activated Carbon Adsorbents Exhibiting High-Capacity, Selective, and Reversible Hydrogen Storage at Room Temperature

Abstract

Storage is one of the main challenges that hinders the wide implementation of hydrogen as a fuel. Focusing on storage at room temperature conditions, metal-decorated activated carbon adsorbents were prepared here by in situ deposition employing three different metals, namely Pd, Pt, and Li, and were comparatively evaluated with respect to hydrogen capacity, kinetics, reversibility, and selective adsorption over N2, CO2, CH4, and O2. The developed metal–AC adsorbents showed competitive storage capacities at room temperature, following the order of Li-AC > Pt-AC > Pd-AC > unmodified AC. Li-AC was the best performing system at 298 K, exhibiting a capacity of 1.44 and 2.06 wt % at 3 and 13 bar, respectively, which were more than 6-fold higher than that of the unmodified AC and among the highest performance values reported in the literature for room temperature storage. Notably, H2/CH4and H2/N2selectivities were 17.6 and 62.6, respectively, at 500 mbar, along with enhanced kinetics and complete reversibility at room temperature upon repeated charge/discharge PSA cycles up to 3 bar. The latter is mainly attributed to the polarization-induced physical interactions of molecular hydrogen with the dispersed Li, rather than chemical interactions by dissociative chemisorption (spillover) or hydride-based binding that dominate the transition metal, Pd-AC and Pt-AC, analogues.