Molten salt-mediated cyano group augmentation and morphology modulation in carbon nitride for boosting photocatalytic activity

Abstract

Graphitic carbon nitride (g-C3N4) is recognized as one of excellent candidate of green photocatalysts due to its unique merits such as low cost, facile synthesis and suitable energy band structure. Herein, we report a systematically optimized carbon nitride catalyst (U1T5-CN-K) integrated cyano group augmentation and morphology modulation, which is synthesized by synergistic combination of potassium ions (K+) molten-salt method and precursor regulation. It is verified that the molten salt method using KCl renders the doping of K+ and formation of cyano (-C≡N) groups. On this basic, the accomplished morphology modulation by regulated precursors significantly enhances the specific surface, which makes the synergistic interplay with K+ dopants for markedly elevating exposed active sites and crystallinity. The K+ primarily enhance oxygen (O2) adsorption capacity and act as electron capture sites based on experimental characterization and theoretical calculations, which effectively suppressed recombination of photogenerated carriers. Meanwhile, -C≡N groups directly or indirectly promote proton (H+) and O2 absorption, thereby advancing the reaction progress. The obtained catalysts exhibit remarkably enhanced spatial charge separation efficiency and reaction kinetics in photocatalytic reactions, delivering a high hydrogen peroxide (H2O2) production rate of 13.7 mmol·g⁻¹·h⁻¹. Moreover, they demonstrate an improved degradation rate of tetracycline hydrochloride (TH), which is ~12 times to that of pristine counterpart. The present work provides some valuable insights on synergistic mechanism by combining group augmentation and morphology modulation for boosting photocatalytic performance of g-C3N4 materials.