A First-Principles Study on Titanium-Decorated Adsorbent for Hydrogen Storage

Insight into the Reversible Hydrogen Storage of Titanium-Decorated Boron-Doped C20 Fullerene: A Theoretical Prediction

Hydrogen storage has been a bottleneck factor for the application of hydrogen energy. Hydrogen storage capacity for titanium-decorated boron-doped C20 fullerenes has been investigated using the density functional theory. Different boron-doped C20 fullerene absorbents are examined to avoid titanium atom clustering. According to our research, with three carbon atoms in the pentagonal ring replaced by boron atoms, the binding interaction between the Ti atom and C20 fullerene is stronger than the cohesive energy of titanium. The calculated results revealed that one Ti atom can reversibly adsorb four H2 molecules with an average adsorption energy of -1.52 eV and an average desorption temperature of 522.5 K. The stability of the best absorbent structure with a gravimetric density of 4.68 wt% has been confirmed by ab initio molecular dynamics simulations. These findings suggest that titanium-decorated boron-doped C20 fullerenes could be considered as a potential candidate for hydrogen storage devices.

Improvement of Hydrogen Adsorption on the Simultaneously Decorated Graphene Sheet with Titanium and Palladium Atoms

In this study, a simultaneously decorated graphene sheet with titanium (Ti) and palladium (Pd) atoms is proposed to improve hydrogen adsorption uptake. Density functional theory (DFT) with a DFT-D3 correction dispersion study was applied. Initially, the hydrogen adsorption energy, energy band gap, partial density of state (PDOS), thermal stability, and H2 desorption temperature for Ti-decorated, Pd-decorated, and Ti-Pd-decorated graphene sheets were investigated. Clustering formation for the Ti-decorated graphene sheet was examined in detail. Grand canonical Monte Carlo (GCMC) simulation was applied to examine the hydrogen adsorption isotherm. Simulation results showed that the hydrogen adsorption energy and desorption temperature of the Ti-decorated graphene sheet are -0.61 eV and 765.4 K, respectively, which are significantly higher than those of the Pd-decorated graphene sheet (-0.108 eV and 135.5 K). However, Ti atoms form clusters when their distances from each other are less than 6 Å. Inserting adaptable metal atoms such as Pd into the Ti-decorated graphene adjusts the hydrogen adsorption energy to -0.544 eV and the desorption temperature to 627.4 K. In addition, the values of Gibbs free energy changes (ΔG) of metal adsorption showed that the Ti-Pd graphene sheet has good stability at different temperatures. Calculated hydrogen adsorption isotherm using the GCMC method approved the suitable performance of the Ti-Pd-decorated graphene sheet for hydrogen adsorption. At the pressure of 60 bar and temperature of 298 K, the hydrogen adsorption content increases from 1.49 wt % on the Ti-decorated graphene sheet with cluster to 2.06 wt % on the Ti-Pd-decorated graphene sheet. Finally, Ti-Pd-decorated graphene sheet was proposed as a novel adsorbent in the hydrogen storage industry.

Density Functional Theory-Based Approaches to Improving Hydrogen Storage in Graphene-Based Materials

Various technologies have been developed for the safe and efficient storage of hydrogen. Hydrogen storage in its solid form is an attractive option to overcome challenges such as storage and cost. Specifically, hydrogen storage in carbon-based structures is a good solution. To date, numerous theoretical studies have explored hydrogen storage in different carbon structures. Consequently, in this review, density functional theory (DFT) studies on hydrogen storage in graphene-based structures are examined in detail. Different modifications of graphene structures to improve their hydrogen storage properties are comprehensively reviewed. To date, various modified graphene structures, such as decorated graphene, doped graphene, graphene with vacancies, graphene with vacancies-doping, as well as decorated-doped graphene, have been explored to modify the reactivity of pristine graphene. Most of these modified graphene structures are good candidates for hydrogen storage. The DFT-based theoretical studies analyzed in this review should motivate experimental groups to experimentally validate the theoretical predictions as many modified graphene systems are shown to be good candidates for hydrogen storage.