The molecular diffusion of ions in energy storage devices, such as, e.g., supercapacitors, is the process enabling their charging and discharging ability. Chmiola et al. demonstrated the strong impact of micropores on the increase of specific capacitance using a series of titanium carbide-derived carbons exhibiting different but precisely uniform pore sizes . An anomalous increase in specific capacitance was observed for those pores being comparable in size to adsorbed electrolyte ions, while the larger pores led to the loss of capacitance. However, under such constraints, one expects kinetic problems caused by confinement-induced obstruction for molecular diffusion .
Only very recently, the direct experimental assessment of the ion transport characteristics within the pores of carbon materials became accessible using the quasielastic neutron scattering  and the pulsed field gradient (PFG) NMR .
Inspired by these recent methodological achievements, we applied the PFG NMR techniques to directly (and selectively) probe the diffusion characteristics of each individual component of organic electrolytes and ionic liquids, that is anion and cation (and solvent, when present), confined to model carbons with uniform and well-defined pore sizes - microporous, mesopores, and with hierarchical pore organization . Quite unexpectedly, it is observed that the presence of a network of mesopores, in addition to smaller micropores—the concept widely used in heterogeneous catalysis to promote diffusion of sorbates—does not necessarily enhance ionic transport in carbon materials.
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