Computational Study of Hydrogen Storage Characteristics of Covalent-Bonded Graphenes

Abstract

We performed first-principles calculations to investigate the hydrogen storage characteristics of carbon-based 3-D solid structures, called covalently bonded graphenes (CBGs). Using the density functional method and the Møller-Plesset perturbation method, we show that H2 molecular binding in the CBGs is stronger than that on an isolated graphene with an increase of 20 to approximately 150% in binding energy, which is very promising for storage at ambient conditions. We also suggest that the CBGs of appropriate size can effectively work as frameworks for transition metal dispersion. The adsorption properties of hydrogen on the metal atoms dispersed inside the CBGs are also presented.

Effect of vacancy defects in graphene on metal anchoring and hydrogen adsorption

“…Recently, several computational studies proposed that transition metal ͑TM͒ dispersed in nanomaterials or polymers can bind hydrogen molecules with appropriate strength so that the storage system filled with such TM complexes can operate at ambient conditions with enough storage capacities. [3][4][5][6][7][8] It was shown that the hydrogen binding energy ranges from 0.3 to 0.7 eV depending on the metal type, and that the effective storage capacity can reach as high as about 6 wt %. [3][4][5][6][7][8] The Kubas interaction between TM atoms and hydrogen molecules was shown to be responsible for enhanced hydrogen adsorption energy.…”

Effective metal dispersion in pyridinelike nitrogen doped graphenes for hydrogen storage

“…The metal-hydrogen binding energy and ratio look very promising with respect to capacity and release temperature. [4][5][6][7][8][9][10][11] However, the issue of structural stability and poor reversibility in TM dispersion has been a major concern as TM atoms tend to easily aggregate instead of being atomistically dispersed. 12,13 Strong metal cohesion is believed to be responsible for the aggregation.…”

“…As a way to overcome such clustering, it was suggested to increase the binding strength between metal and dispersant materials by introducing structural or chemical defects. 10,11 For example, boron doping in graphitic materials was shown to improve dramatically the metal dispersion and the hydrogen adsorption. 11 In this letter, we study pyridinelike nitrogen doped graphene ͑PNG͒ as an effective medium for TM ͑Sc, Ti, and V͒ atomic dispersion.…”

“…20,21 The LDA ͑GGA͒ gives an upper ͑lower͒ bound for hydrogen binding energy calculated with more correlated methods such as coupled-cluster singles and doubles with perturbative triples correction. 10 Presented below are the LDA results unless specified otherwise. The cutoff energy for the plane-wave basis is 400 eV, and the atomic relaxation is carried out until the Helmann-Feynman forces on atoms are less than 0.01 eV/ Å.…”

Environmental applications using graphene composites: water remediation and gas adsorption

“…157,158 By calculations of graphene buckling, convex regions in corrugated graphene are energetically favorable for hydrogen binding. 159 A corrugated graphene multilayer system can reversibly store hydrogen with a maximum capacity of 8 wt% under ambient conditions by controlling the local curvature.…”