Enhanced hydrogen adsorption properties of Zeolite Templated Carbon via chemical activation: DFT study

In this study, Density Functional Theory (DFT) simulation method was applied to show that hydrogen-storage properties of Zeolite Templated Carbon (ZTC) can be enhanced via chemical activation. Study results calculated via simulation and the Monte Carlo integration technique showed that in comparison to unactivated ZTC, the theoretical specific surface area (SSA) for Zeolite Templated Activated Carbon (ZTAC) increased by 4.79 and 2.13 %, when activated with either Zinc dichloride (ZnCl2) or Potassium Hydroxide (KOH), respectively. In addition, calculation of accessible surface area (ASA) resulted in 7809.40 m(2)/g and 7611.74 m(2)/g, correspondingly. Simulations of H-2 adsorption revealed that H-2 molecules were adsorbed primarily on the concave region of the ZTAC. Also, it was found the that the largest amount of H-2 adsorbed molecules on ZTAC activated with either ZnCl2 or KOH were 13 and 15, and the average binding energies were 0.184 eV and 0.202 eV, respectively. In this regard, the maximum hydrogen storage capacity obtained in this study was 5.2 wt% (ZTAC-13H(2)) and 5.95 wt% (ZTAC-15H(2)) with a volumetric density of 0.065 kg H-2/L and 0.074 kg H-2/L for the ZTAC activated with either ZnCl2 or KOH. These results are in accordance with the U.S. Department of Energy (DOE) ultimate target by the 2025 year. In addition, thermal stability and desorption temperatures of ZTAC structures were determined via molecular dynamics simulations and through the van't Hoff equation, showing that hydrogen molecules were easy to desorb at room temperature (T=300 K). These results pose these systems suitable for automotive onboard applications, leading to future research on synthesis techniques of ZTAC materials which certainly require more experimental investigation.