g-C3N4/Nitrogen-Doped Carbon Dot/Silver Nanoparticle-Based Ternary Photocatalyst for Water Pollutant Treatment

The graphitic carbon nitride (g-C3N4)/nitrogen-doped carbon dots (NCDs)/silver (Ag) ternary composite catalysts for organic pollution degradation in aqueous solution were constructed using an interfacial electronic control mechanism with double doping of NCDs and Ag nanoparticles (NPs). NCDs can act as a bridge for electrons to guide the flow of photogenerated charge carriers. The Ag NPs acts as photo-sensitizers and electron acceptors, enhancing electron transport in the material. With the synergistic effect of NCDs and Ag NPs, the absorption range of the visible spectrum of the g-C3N4/NCDs/Ag catalyst is broadened, the excitation of electrons is enhanced, and the photogenerated electron-hole binding rate is slowed down. The experimental results showed that the degradation of several contaminants [methyl orange (MO), rhodamine B (Rh B), tetracycline hydrochloride, and chrysin hydrochloride] could be achieved within 100 min using a 300 W xenon lamp as the light source (lambda > 400 nm). It is very noteworthy that the reaction rates of g-C3N4/ NCDs/Ag catalysts for the degradation of MO and Rh B were 13.5 and 12.9 times higher than those of conventional g-C3N4, respectively. NCDs and Ag NPs are uniformly distributed inside the material by inducing g-C3N4 to undergo self-assembly, and thus the g-C3N4/NCDs/Ag catalysts exhibit a stable recycling performance. In addition, center dot O2- was confirmed as the main active substance in the photocatalytic process by radical capture experiments and EPR tests, and center dot OH was used as a secondary site to assist in the photocatalytic degradation process. This design idea of a double-doped modulated g-C3N4 material is expected to be applied in more fields.