Structural Insights on Nitrogen-Containing Hydrothermal Carbon Using Solid-State Magic Angle Spinning ¹³C and ¹⁵N Nuclear Magnetic Resonance

Here, ¹³C and ¹⁵N solid state NMR is used as the main and most effective characterization technique on nitrogen-containing hydrothermal carbons obtained from glucose and glycine. This study represents a model system for other types of nitrogen-containing hydrothermal carbons, which were shown to have interesting energy-storage properties (Zhao et al. Adv. Mater. 2010, 22, 5202). These materials are obtained either from N-containing carbohydrates or from pure carbohydrates in the presence of natural amino-containing compounds such as proteins or aminoacids. In contrast to what is generally known for this model system, high molecular weight heterogeneous polymers (e.g., melanoidins) that are formed when sugars and amino acids combine through the Maillard reaction, we found an extended nitrogen-containing aromatic network, which is chemically bound to a polyfuran network known to be one of the main components of the biomass-derived hydrothermal carbons. In contrast to the hydrothermal carbons obtained from pure carbohydrates, these types of N-containing materials have an increased level of aromatic character already present at 180 °C, after the hydrothermal treatment.