Cooperative physisorption and chemisorption of hydrogen on vanadium-decorated benzene

Abstract

3d TM-decorated carbon composites have been proved to be a new generation of hydrogen storage materials. However, detailed hydrogen storage mechanisms are still unclear. Investigation of the H₂ dissociation and H migration on the 3d TM-decorated six-membered carbocycles is very critical for better understanding the hydrogen storage mechanism. In this paper, the processes of chemisorption and physisorption of multiple H₂ molecules on synthesized VC₆H₆ were simultaneously investigated for the first time. The Gibbs free energy calculations show that the optimal chemisorption pathway with the hydrogen storage capacity of 5.97 wt% is exothermic by 2.83 kcal mol⁻¹. Both the continuous hydrogenation giving the product of VC₆H₁₁–3H and reverse dehydrogenation could run smoothly at room temperature. The physisorption with a hydrogen storage capacity of 4.48 wt% will be exothermic by 13.49 kcal mol⁻¹. The H₂ molecules can be physisorbed at any temperature under 416 K and readily desorbed above 480 K at 1 atm. In summary, physisorption and chemisorption synergistically boost the hydrogen storage property of complex VC₆H₆. Our study provides a comprehensive picture of the interaction between hydrogen and VC₆H₆ and opens a new window for optimizing the future hydrogen storage materials.