Exceptional Hydrogen Storage Performance of Ti-Decorated C₃B₂ Quantum Dot: A Comprehensive First-Principles Study

The development of lightweight materials with high and reversible hydrogen storage capacity remains a key materials design challenge. Here, we investigate pristine and Ti-decorated C₃B₂ quantum dots using DFT, DLPNO-CCSD(T), and statistical thermodynamics. Pristine C₃B₂ strongly chemisorbs H₂ (E_ads = -0.93 eV), while Ti decoration moderates the interaction to a reversible regime (E_ads = -0.39 eV) through a balanced Kubas-type mechanism. Structural analysis shows that the Ti center becomes saturated at approximately five H₂ molecules via Kubas-type coordination, while additional hydrogen molecules are stabilized in the vicinity of the Ti-C₃B₂ framework through cooperative interactions. Sequential adsorption shows that up to 20 H₂ molecules can be stored per Ti-C₃B₂ unit. Thermodynamic and kinetic analyses reveal moderate desorption temperatures (≈322-366 K) and ultrafast release times, ensuring efficient cycling. Under realistic operating conditions (30/3 atm; 298/373 K), Ti-C₃B₂ achieves a reversible capacity of 20.10 wt%, surpassing DOE targets. These results highlight Ti-decorated C₃B₂ quantum dots as a promising, design-tunable platform for next-generation solid-state hydrogen storage.