How chemical defects influence the charging of nanoporous carbon supercapacitors.

SignificanceNanoporous carbon texture makes fundamental understanding of the electrochemical processes challenging. Based on density functional theory (DFT) results, the proposed atomistic approach takes into account topological and chemical defects of the electrodes and attributes to them a partial charge that depends on the applied voltage. Using a realistic carbon nanotexture, a model is developed to simulate the ionic charge both at the surface and in the subnanometric pores of the electrodes of a supercapacitor.

Timescale prediction of complex multi-barrier pathways using flux sampling molecular dynamics and 1D kinetic integration: Application to cellulose dehydration.

Reactive molecular dynamics (MD) simulations, especially those employing acceleration techniques, can provide useful insights on the mechanism underlying the transformation of buried organic matter, yet, so far, it remains extremely difficult to predict the time scales associated with these processes at moderate temperatures (i.e., when such time scales are considerably larger than those accessible to MD).

Methane Diffusion in a Flexible Kerogen Matrix.

It has been recognized that the microporosity of shale organic matter, especially that of kerogen, strongly affects the hydrocarbon recovery process from unconventional reservoirs. So far, the numerical studies on hydrocarbon transport through the microporous phase of kerogen have neglected the effect of poromechanics, that is, the adsorption-induced deformations, by considering kerogen as a frozen, nondeformable, matrix. Here, we use molecular dynamics simulations to investigate methane diffusion in an immature (i.

Poroelasticity of Methane-Loaded Mature and Immature Kerogen from Molecular Simulations.

While hydrocarbon expulsion from kerogen is certainly the key step in shale oil/gas recovery, the poromechanical couplings governing this desorption process, taking place under a significant pressure gradient, are still poorly understood. Especially, most molecular simulation investigations of hydrocarbon adsorption and transport in kerogen have so far been performed under the rigid matrix approximation, implying that the pore space is independent of pressure, temperature, and fluid loading, or in other words, neglecting poromechanics. Here, using two hydrogenated porous carbon models as proxies for immature and overmature kerogen, that is, highly aliphatic hydrogen-rich vs highly aromatic hydrogen-poor models, we perform an extensive molecular-dynamics-based investigation of the evolution of the poroelastic properties of those matrices with respect to temperature, external pressure, and methane loading as a prototype alkane molecule.