Fabrication of Single‐Layer Graphitic Carbon Nitride and Coupled Systems for the Photocatalytic Degradation of Dyes under Visible‐Light Irradiation

A coupled system for the photocatalytic degradation of rhodamine B (RhB) was realized by a CdS/SL g‐C 3 N 4 (SL g‐C 3 N 4 = single‐layer graphitic carbon nitride) photocatalyst under visible‐light irradiation. SL g‐C 3 N 4 was fabricated by the ultrasonic exfoliation of bulk g‐C 3 N 4 . Two series of CdS/SL g‐C 3 N 4 and CdS/g‐C 3 N 4 photocatalysts with different CdS content were prepared by a hydrothermal process. The photocatalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), UV/Vis diffuse reflection spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X‐ray photoelectron spectroscopy (XPS), and transient photocurrent measurements. Compared with those of pure bulk g‐C 3 N 4 , CdS, and SL g‐C 3 N 4 , the samples of the CdS/SL g‐C 3 N 4 photocatalyst series exhibited enhanced photocatalytic activities and excellent photostabilities under visible‐light irradiation. With an optimum CdS content of 33.3 % and a reaction time of 120 min, the RhB degradation efficiency reached 99.55 % under visible‐light irradiation. From a first‐order model, the rate constant ( k ) of the 33.3 % CdS/SL g‐C 3 N 4 photocatalyst is up to 13.59, 6.10, and 4.54 times those of bulk g‐C 3 N 4 , SL g‐C 3 N 4 , and CdS, respectively. On the basis of the corresponding energy band positions, a mechanism for enhanced photocatalytic activity is proposed. Owing to the excellent performance of the CdS/SL g‐C 3 N 4 series, a visible‐light‐responsive and environmentally friendly photocatalyst for the degradation of dyes was obtained.