Unveiling the effect of the polymerization degree of graphitic carbon nitride on the surface functionalization by low-temperature plasma: Insights from XPS and DFT study

Abstract

This study investigates the electronic structure and surface chemistry of graphitic carbon nitride (gCN) with distinct degrees of polymerization. We compare gCN materials prepared via conventional pyrolysis of melamine (M−gCN) and pyrolysis of a melamine-cyanuric acid complex (CM-gCN). Using.

X-ray photoelectron spectroscopy (XPS) and Density functional theory (DFT) calculations, we provide unique comparison of melon and fully-heptazine based gCN structures, enabling precise identification of core-level XPS components and resolving common discrepancies in the literature. To introduce carboxyl (COOH), amide (CONH₂), and amine (NH₂) groups on the surface of gCN, both materials.

(M−gCN−PT and CM-gCN-PT) were treated by low-temperature air plasma and the presence of these groups was confirmed by XPS and DFT analysis. We demonstrate that the polymerization degree of gCN influences the concentration and orientation of surface functional groups, with differences observed in the amide group binding depending on the gCN structure. We also discuss influence of surface functional groups on the band structure of the materials experimentally by valence band XPS spectra and DFT simulations by comparing calculated projected density of states (PDOS). This work highlights the critical role of polymerization in optimizing the functionalization efficiency of gCN, providing valuable insights for enhancing its performance in practical applications.