Room‐Temperature Reversible Hydrogen Storage in Scandium‐Decorated [6]Cycloparaphenylene: Computational Insights

Abstract

This study discusses the hydrogen storage and delivery capacity of Sc‐decorated [6]cycloparaphenylene ([6]CPP) using dispersion‐corrected density functional theory calculations (DFT + D3). The scandium atoms are decorated over [6]CPP via Dewar coordination with an average binding energy of 1.33 eV. Each Sc atom stores up to 5H2 molecules in quasi‐molecular form at an average adsorption energy ranging from 0.23 to 0.36 eV/H2. The system's stability before and after H2 adsorption is checked using reactivity parameters. The maximum hydrogen gravimetric capacity of the system is found to be 7.68 wt% at low temperatures at 1–60 bar pressure. With an increase in temperature (300–420 K), the gravimetric density is more than 5.5 wt% (US‐DOE target) below 60 bar. Atom‐Centered Density Matrix Propagation (ADMP)‐molecular dynamics (MD) simulations reveal that the desorption of H2 molecules from [6]CPP starts at around 300 K/1 bar, and complete desorption occurs above 480 K. The minimum Van't Hoff desorption temperature for [6]CPP‐Sc is 296.9 K at 1 atm pressure. Insignificant change in the structure of [6]CPP‐Sc during adsorption and desorption processes promises stability and reversibility of the system. Hence, we believe that Sc‐decorated [6]CPP can be a promising candidate for hydrogen storage applications.