In situ NMR spectroscopic investigations of ion adsorption mechanisms on nanoporous carbon materials

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Nanoporous carbon materials have gained increasing interest for electrochemical energy storage due to their outstanding materials properties such as high electrical conductivity, chemical and thermal stability, and especially due to their large electrolyte-accessible internal surfaces. NMR spectroscopic methods increasingly contribute to the understanding of the molecular processes in battery and electrode materials. In addition to materials and surface characterization, NMR spectroscopic studies also allow investigating the interactions between electrode materials and electrolyte molecules. Meanwhile, this can be even done by in situ NMR spectroscopy of charged devices. Within the present project, well-defined, idealized model materials with typified pore size distributions and surface functionalities will be synthesized for the identification of characteristic NMR signatures of adsorbed ions. Combined with innovative in situ characterization techniques, this will lead to detailed mechanistic conclusions concerning the molecular processes taking place during electro-adsorption. The planned investigations include: (i) Preparation and characterization of defined model materials with tailored pore sizes and surface functionalities (e.g., carbon materials with mono- or multimodal pore size distribution, with or without polar surface functionalization etc.). (ii) Solid-state NMR spectroscopic characterization of the interactions between the surface of the carbon materials and electrolyte molecules with and without applied voltage. (iii) Analysis of the pore filling mechanisms (adsorption isotherms) using quantitative liquid-state NMR spectroscopy. Moreover, insights into dynamics and adsorption kinetics will be gained. The understanding of these molecular mechanisms will contribute to derive rational design principles for the fabrication of improved electrodes for supercaps and other electrochemical energy storage devices.