Water Confinement in Nitrogen‐Rich Nanoporous Carbon Materials Revealed by In Situ Scanning Transmission X‐Ray Microscopy

Abstract The interaction between water molecules and surfaces in porous carbon‐based materials plays a significant role in various fields including but not limited to catalysis, gas sorption, or electrochemical energy storage and conversion. The incorporation of nitrogen enhances the hydrophilicity of typically rather nonpolar carbon‐based materials but the molecular understanding of water chemical configuration in such porous materials remains incomplete. Water adsorption on nitrogen‐containing nanoporous carbon surfaces is governed by a subtle balance between water–water and water–surface hydrogen bonding interactions, which together determine the water structures formed and their stability. In this work, in situ Scanning Transmission X‐ray microscopy performed on individual nanoporous carbon particles under a humid atmosphere is used to elucidate the interactions between nitrogen‐containing carbon surfaces and water molecules. The hydrogen bonding of water is found to be nonuniform within the particles and to depend on the nanopore size and the chemical bonding of nitrogen atoms. The nature of the nitrogen sites interacting with water is further characterized by resonance inelastic X‐ray Scattering and near ambient pressure X‐ray Photoelectron Spectroscopy. This study provides new perspectives on water interaction when confined in nanoporous nitrogen‐rich carbons.