Study of 2D MXene Cr2C material for hydrogen storage using density functional theory

Hydrogen storage capacity of 2D MXene Cr2C has been studied using density functional theory. Possibility to adsorb H-2 molecule on Cr2C surface at various sites has been studied. Among the studied adsorption sites on Cr2C surface, few sites were found suitable for chemisorption and physisorption of H-2 molecules. Few of the studied sites are also found to be suitable for Kubas-type interaction, which is useful for reversible hydrogen storage at ambient conditions. Electronic structure calculations and charge transfer analysis have been done to understand the interactions of adsorbed hydrogen with the Cr2C layer. It has been found that the total hydrogen storage capacity of Cr2C is 7.6 wt.% in which 1.2 wt.% of H is due to the chemisorption, 3.2 wt.% is bonded with Kubas-interaction and remaining 3.2 wt.% is bonded through weak electrostatic interactions (with binding energy of 0.26 eV/H-2 and charge transfer of 0.09 e(-) to H atom from Cr atom). Thus the reversible hydrogen storage capacity at ambient conditions (controlled by hydrogen bonded with energies ranging from 0.1 to 0.4 eV/H-2, in the present case through Kubas and weak electrostatic interactions) is 6.4 wt.% which is greater than the 2017 DoE recommended target value of 5.5 wt.%.