Critical insight on the hydrothermal effects toward exfoliation of g-C ₃ N ₄ and simultaneous in-situ deposition of carbon quantum dots

In this study, exfoliated g-C ₃ N ₄ (GCN) coupled carbon quantum dots (CNQDs) were prepared via one-pot hydrothermal (HT) treatment at various temperatures (100–200 °C) and in various amounts of time (0–20 h). Comprehensive characterization was conducted to study not only the chemical states, photo-optical properties, particle sizes, and crystal structures, but also the effect of these changes on the degradation of BPA. Photocatalytic degradation was conducted under near-visible LED as a low energy light source (0.128 W cm ⁻³ ). The CNQD that were prepared at 180 °C for 12 h showed the highest degradation rate (3.6 × 10 ⁻² min ⁻¹ ), which was 3.0 times higher than GCN. These improved photocatalytic activities corresponded to increases in the photo-reactive surface via exfoliation of GCN sheets, introduction of heteroatom oxygen onto GCN sheets, the addition of CQDs, and shortened bandgap. These characteristics allow for the effective transfer and separation of electrons. Nonetheless, the structural breakdown of the CNQD was observed when the HT time was longer than 12 h (180 °C). The defected sheets showed a detrimental effect towards photocatalytic degradation by trapping electrons, leading to shorter electron life times.