Toward Efficient Hydrogen Storage: A Quantum Chemical Study of Beryllium Clusters

High Resolution Image Download MS PowerPoint Slide The development of lightweight materials capable of reversibly storing hydrogen under practical conditions remains a central challenge for hydrogen-based energy technologies. In this work, a systematic density functional theory (DFT) investigation is carried out to evaluate the structural stability and hydrogen adsorption properties of beryllium clusters (Be n, n = 3–25). Benchmark calculations against DLPNO-CCSD(T) confirm that the ωB97X-3c composite functional provides an accurate and efficient description of Be–Be bonding and H 2 adsorption energetics across the full-size range. Single-molecule adsorption reveals predominantly molecular physisorption for most clusters, with adsorption energies lying in the optimal window for reversible hydrogen storage and negligible H–H bond activation. Detailed multi-H 2 adsorption studies on representative clusters (Be 3, Be 1 4, and Be 2 4 ) highlight a pronounced size dependence. Among them, the medium-sized Be 1 4 cluster exhibits exceptional performance, accommodating up to 20H 2 molecules with smoothly decreasing average adsorption energies from −0.35 to −0.10 eV per H 2 . This behavior enables a high theoretical gravimetric hydrogen density of 24.2 wt % and a reversible working capacity of 17.86 wt %, significantly exceeding the DOE 2025 target. Thermodynamic and kinetic analyses predict favorable desorption temperatures (127–259 K) and ultrafast desorption kinetics. Electronic structure analyses, including energy decomposition, density of states, and IGMH methods, reveal that hydrogen uptake is governed by cooperative, noncovalent interactions dominated by electrostatic, polarization, and dispersion contributions. These results identify Be 1 4 as a promising nanoscale motif for reversible hydrogen storage and provide fundamental insights into size-dependent hydrogen adsorption in light-element clusters.