A novel method for synthesizing β-C3N4 using the plasma-liquid technique

Abstract

Carbon nitride (C3N4), particularly its β-phase, has garnered significant interest due to its exceptional mechanical properties, wide bandgap, and potential applications in photocatalysis and optoelectronics. However, synthesizing phase-pure β-C3N4 remains challenging due to its thermodynamic instability under ambient conditions. In this study, we present a novel, single-step plasma-liquid synthesis method for β-C3N4, utilizing pulsed DC discharge between graphite electrodes submerged in either an aqueous urea solution or acetonitrile. The synthesized materials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, and transmission electron microscopy (TEM). XRD confirmed the formation of β-C3N4, and the average crystallite size, determined using the Debye-Scherrer formula, was found to range between 16 and 18 nm, while FTIR revealed characteristic C[sbnd]N bonding networks. Optical bandgap measurements yielded values of 3.8 eV for the urea-derived sample and 3.45 eV for the acetonitrile-derived sample. TEM analysis demonstrated sheet-like morphologies with varying porosity, and zeta potential measurements indicated moderate colloidal stability. The photocatalytic degradation kinetics of dyes mixture of Rhodamine B (RhB), Reactive Red 6C (RR6C), and Methylene Blue (MB) were investigated using β-C3N4 samples, revealing distinct adsorption and degradation behaviors. A notable kinetic acceleration after 30 min suggested autocatalytic effects from intermediate products. Compared to g-C3N4, β-C3N4 exhibited 1.5 to 2 times higher degradation rates, attributed to enhanced crystallinity, reduced defects, and improved charge separation. The proposed method offers a cost-effective, environmentally friendly, and scalable approach for β-C3N4 synthesis, eliminating the need for high-pressure or high-temperature conditions.