High capacity reversible hydrogen storage in titanium doped 2D carbon allotrope Ψ-graphene: Density Functional Theory investigations

Using the state-of-the art Density Functional Theory simulations, here we report the hydrogen storage capability in titanium decorated Psi-Graphene, an advanced 2D allotrope of carbon which is made of hexagonal, pentagonal and heptagonal ring of carbon and metallic in nature. Titanium is strongly bonded on the surface of Psi-Graphene and each Ti can bind maximum of 9H(2) having average adsorption energy of -0.30 eV and average desorption temperature of 387 K yielding gravimetric H-2 uptake of 13.14 wt%, much higher than the prescribed limit of 6.5 wt % by DoE's. The interaction of Ti on Psi-Graphene have been presented by electronic density of states analysis, charge transfer and plot for spatial distribution of charge. There is orbital interaction between Ti 3d and C 2p of Psi-Graphene involving transfer of charge whereas bonding of hydrogen molecules is through Kubas type of interactions involving charge donation from a orbitals of hydrogen molecules to the vacant 3d orbital of Ti and the subsequent back donation to sigma* orbital of hydrogen from filled 3d orbital of Ti. The structural stability of the system at temperatures corresponding to the highest temperature at which H-2 desorbs was verified using ab-initio Molecular Dynamics calculations and presence of sufficient energy barrier for diffusion which prevents clustering between metal atoms assures the practical viability of the system as high capacity H-2 adsorbing material. Overall, found that Ti doped Psi-Graphene is stable, 100% recyclable and has high hydrogen storage capacity with suitable desorption temperature. As a result of our findings, we are confident that Ti doped Psi-Craphene may be used as a potential hydrogen adsorbing material in the upcoming clean, green, hydrogen economy. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Titanium-modified Psi-Graphene has been shown to have high stability, 100% recyclability, and high hydrogen storage capacity with suitable desorption temperature, making it a potential material for hydrogen storage in the future clean, green hydrogen economy.