On the hydrogen storage performance of Cu-doped and Cu-decorated graphene quantum dots: a computational study

Abstract

Hydrogen gas is a promising renewable energy source. The hydrogen storage performance of two differently modified graphene surfaces, particularly Cu-doped and Cu-decorated circumcoronene (CC), is investigated using density functional theory, 6-311G* basis set and Bader's quantum theory of atoms in molecules (QTAIM). It is found that the Cu-doped CC is able to bind three H 2 molecules on one Cu atom, while the Cu-decorated CC is able to bind up to five H 2 molecules on one Cu atom. Changes in the topology of charge density upon the H 2 adsorption are evaluated under the formalism of QTAIM analysis. The QTAIM analysis of bond critical points as well as the density of states analysis show that the interaction between Cu and adsorbed H 2 molecules can be considered as a physisorption (a van der Waals type interaction). Overall, the results presented in this study point out that the Cu-decorated graphene surfaces are more suitable potential candidates for hydrogen storage than the Cu-doped ones. Furthermore, the inclusion of diffuse functions in the basis set is critically considered.

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

“…Ample reports of DFT studies on hydrogen storage on decorated graphene are available in the literature [ 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 ]. Single-atom decoration is the commonly used strategy to decorate graphene [ 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ,…”

“…The commonly used elements for decoration are Li, Ca, Ti, and Pd. Interestingly, several studies have considered dispersion corrections that substantially improve the description of the interaction between H 2 and decorated graphene [ 50 , 52 , 53 , 56 , 60 , 62 , 68 , 72 , 73 , 74 , 75 , 81 , 83 , 85 , 86 , 90 , 91 , 93 ]. When the hydrogen molecule is adsorbed on graphene decorated with single-atoms, hydrogen is adsorbed on the decorating atoms as they function as active centers.…”

Hetero-atom doped graphene for marvellous hydrogen storage: unveiling recent advances and future pathways

“…TM atoms are recommended to build up the synergy between hydrogen molecules/atoms and the graphene substrate. 88,[141][142][143][144] Doping and decoration of TM atoms improve the bonding propensity of hydrogen due to the hybridization of TM atoms' d-orbitals with the hydrogen s or s* orbitals. In ambient temperature hydrogen storage, TM doping increases the adsorption energy of hydrogen molecules, which is followed by a Kubas-type interaction (15-20 kJ mol −1 ) and a spillover activity.…”

Recent progress of quantum dots for energy storage applications

“…Therefore, graphene QDs is considered as a potential candidate material for solid-state hydrogen storage. However, the research on QDs hydrogen storage is almost blank, and only a few researchers try to dope Pb, [155] Cu, [69] Cr, [156] Li [70] and other metals in QDs to improve the performance of hydrogen storage. No QDs composite material for hydrogen storage has been prepared so far, which leaves us a promising but unexplored field.…”

“…Elsayed et al prepared heterogeneous photocatalysts in the form of polymer dots by combining organic semiconductor polymers with N-doped carbon quantum dots covered by PS-PEGCOOh, and its hydrogen evolution rate increased by about five times [68]. In addition, heteroatoms doped on QDs can form strong interactions with hydrogen, increasing adsorption capacity, which is also promising for hydrogen storage [69,70].…”