Simulations of volumetric hydrogen storage capacities of nanoporous carbons: Effect of dispersion interactions as a function of pressure, temperature and pore width

Abstract

Simulations of the hydrogen storage capacities of activated carbons require an accurate treatment of the interaction of a hydrogen molecule physisorbed on the graphitic-like surfaces of nanoporous carbons, which is dominated by the dispersion interactions. These interactions are described accurately by high level quantum chemistry methods such as the Coupled cluster method with single and double excitations and a non-iterative correction for triple excitations (CCSD(T)), but those methods are computationally very expensive for large systems and massive simulations. Density functional theory (DFT) based methods that include dispersion interactions are less accurate, but computationally less expensive. Calculations of the volumetric hydrogen storage capacities of nanoporous carbons, simulated as benzene and graphene slit-shaped pores, have been carried out, using a quantum-thermodynamic model of the physisorption of H 2 on surfaces and the interaction potential energy curves of H 2 physisorbed on benzene and graphene obtained using the CCSD(T) and second order Møller-Plesset (MP2) methods and the 14 most popular DFT-based methods that include the dispersion interactions at different levels of complexity. The effect of the dispersion interactions on the DFT-based volumetric capacities as a function of the pressure, temperature and pore width is evaluated. The error of the volumetric capacities obtained with the quantum-thermodynamic model and each method is also calculated and analyzed.

Li-decorated BC3 nanopores: Promising materials for hydrogen storage

“…Regarding the way we use to simulate the local environment of a porous material based on BC 3 , it is important to remark that the pioneering experiments by Franklin [63] and the results of more recent experimental studies on nanoporous carbons [64,65] showed that these materials are mainly composed by slit-shaped pores, with a pore width distribution in the range of several to hundred angstroms. Previous calculations for graphene slit pores (i.e., two parallel graphene sheets separated by a distance in the range of nanometers) confirm that the local environment of porous carbon materials is well captured by means of such slit pores [21,60,61]. In the present work, slit pores made of two parallel BC 3 sheets in their most stable honeycomb configuration are used in the simulations.…”

“…The aim of the work presented here is to provide realistic predictions for the volumetric and gravimetric hydrogen storage capacities of a porous material containing Li-decorated BC 3 slit pores. To incorporate finite temperature and pressure, we combine results obtained from DFT calculations with those inferred from a quantum-thermodynamic model [21,[59][60][61][62]. A similar methodology has been used recently by us to investigate the hydrogen storage capacity of Li-decorated borophene slit pores, which were found to be optimal for hydrogen storage at low temperature [59].…”

Hydrogen storage capacity of Li-decorated borophene and pristine graphene slit pores: A combined ab initio and quantum-thermodynamic study

“…Graphene slit pores were studied in Ref. [44] using the optB88-vdW functional, with the aforementioned approximation for the interaction potential of H 2 with graphene. The volumetric capacities, v c , of graphene slit pores published in Ref.…”

“…The volumetric capacities, v c , of graphene slit pores published in Ref. [44] will be plotted in this work, for comparative purposes. Other results presented here for graphene slit pores (the gravimetric capacities, g c , and the interaction potentials) are entirely new, although related with the results reported in that reference.…”

“…The quantum-thermodynamic model has been explained in detail in Refs. [21,22,44]. The model is based on considering the thermodynamic equilibrium between the adsorbed and compressed phases of hydrogen gas inside a slit pore.…”