Synchrotron based NEXAFS study on nitrogen doped hydrothermal carbon: Insights into surface functionalities and formation mechanisms

Abstract

Synchrotron-based Near-Edge X-ray Absorption Fine Structure (NEXAFS) studies have been conducted on two hydrothermally produced carbon (HTC) structures and their main surface structural features are reported. The two HTCs were produced respectively from sucrose, and sucrose with added (NH4)2SO4, under subcritical water conditions. The NEXAFS carbon K-edge spectra reveal the presence of CC, COC (furan), CO and COH functionalities on the surface of the sucrose derived HTC. For the nitrogen-doped HTC, the carbon K-edge spectra indicate an increase in CC and COH functionalities, as well as the inclusion of CN and CN functionalities. Additionally, the nitrogen K-edge for the doped hydrothermal carbon displayed characteristic peaks for pyridinic, pyrrolic and tertiary amine nitrogen surface groups. Furthermore, a mechanistic pathway to inclusion of nitrogen atoms in the HTC-SAS structure is postulated.