Modern advanced energy storage and conversion devices based on aqueous electrolytes are among the most promising technologies to support electricity-based renewable energy grids. In such systems, carbon-based materials are the preferred choice for the fabrication of electrodes because i) other elements (heteroatoms) can be easily incorporated into the carbon framework; ii) they can be designed to have porous structures with nanoscale pores of different sizes; iii) their synthesis is sustainable, involves few steps and utilises bio-based feedstocks.

The modification of carbon nanopore structures and the fine-tuning of carbon surface chemistry provide a well-equipped toolset for the production of "designer carbons". Depending on these parameters, properties such as electron density at the surface and morphology change, which strongly influences the exchange with water-based electrolytes. Pure carbon materials (e.g. graphite or activated carbon) are typically considered hydrophobic, while according to vapour adsorption isotherms or contact angle measurements, doped carbon surfaces with more polar heteroatoms such as nitrogen or oxygen are more hydrophilic. However, the transfer of "wettability" from smooth carbon surfaces to carbon nanostructures is not trivial: nanopores produce confinement effects, and heteroatom doping profoundly changes the electron density of carbon, sponsors hydrogen bond formation and can lead to misinterpretations of electrochemical properties.

Understanding water interactions with nanopores of carbonaceous materials is critical for green energy storage and conversion applications, as carbon-electrolyte (carbon-water) interfaces have a dominant influence on electrochemical performance.

NMR spectroscopy is a versatile tool to study localised environments of water in pores, as a clear shift of the signal to higher fields is observed when water enters such pores - caused by the proximity of the water molecules to the ring currents of the carbon structures. Initial results from solid-state nuclear magnetic resonance spectroscopy (ssNMR) show that untreated carbon nanopores are easily filled with water, whereas this may not be the case for highly nitrogen-doped carbons. Although this effect has been intensively studied in pure carbon materials, heavily doped systems are poorly understood.

We are working to close this knowledge gap in the fundamental understanding of such interactions.