Optimization of the Urbach energy and charge carrier dynamics in g-C3N4 through strategic potassium precursor selection: Insights and challenges
Ladislav Svoboda, Zuzana Vilamová, Petr Praus, Vlastimil Novák, Kateřina Mamulová Kutláková, Martin Petr, J. Bednář, Vít Jochim, Zuzana Šimonová, Richard Dvorský
Abstract
The previous studies on K-doped g-C 3 N 4 suggest a simple correlation between the increased potassium content and the improved photocatalytic activity due to a shift of the valence band potential to more positive values, leading to the direct oxidation of hydroxyl ions to hydroxyl radicals by holes. In this study, we investigated the influence of different potassium precursors on the properties and photocatalytic efficiency of K-modified g-C 3 N 4 materials in Rhodamine B degradation. Detailed characterization revealed that the choice of precursor significantly affects the structural and optoelectronic properties with complex correlations rather than superficial relationships between potassium content and photocatalytic activity. Notably, KCl-based samples, despite having a lower specific surface area, exhibited enhanced photocatalytic properties due to prolonged carrier lifetimes and improved charge transfer efficiency compared to KOH-based samples. Higher precursor concentrations resulted in more recombination centers, increasing Urbach energy and reducing photocatalytic activity. These findings underscore the importance of precise synthesis control, revealing that both K and Cl atoms act as charge transfer bridges, improving the material’s photocatalytic properties beyond mere surface area enhancement. In addition, even smaller amounts of Cl atoms in g-C 3 N 4 showed much higher impact on the final position of conduction and valence band potentials than K atoms.