Herein, Fe-doped C₃N₄ high-performance photocatalysts, synthesized by a facile and cost effective heat stirring method, were investigated systematically using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area measurement, X-ray photoelectron (XPS), UV–Vis diffusion reflectance (DRS) and photoluminescence (PL) spectroscopy. The results showed that Fe ions incorporated into a g-C₃N₄ nanosheet in both +3 and +2 oxidation states and in interstitial configuration. Absorption edge shifted slightly toward the red light along with an increase of absorbance in the wavelength range of 430–570 nm. Specific surface area increased with the incorporation of Fe into g-C₃N₄ lattice, reaching the highest value at the sample doped with 7 mol% Fe (FeCN7). A sharp decrease in PL intensity with increasing Fe content is an indirect evidence showing that electron-hole pair recombination rate decreased. Interestingly, Fe-doped g-C₃N₄ nanosheets present a superior photocatalytic activity compared to pure g-C₃N₄ in decomposing RhB solution. FeCN7 sample exhibits the highest photocatalytic efficiency, decomposing almost completely RhB 10 ppm solution after 30 min of xenon lamp illumination with a reaction rate approximately ten times greater than that of pure g-C₃N₄ nanosheet. This is in an agreement with the BET measurement and photoluminescence result which shows that FeCN7 possesses the largest specific surface area and low electron-hole recombination rate. The mechanism of photocatalytic enhancement is mainly explained through the charge transfer processes related to Fe²⁺/Fe³⁺ impurity in g-C₃N₄ crystal lattice.

In this paper, silver (Ag) nanoclusters-loaded graphitic carbon nitride (g-C₃N₄) nanosheets are synthesized and their physical properties as well as photocatalytic activities are systematically investigated by different techniques. The existence of Ag atoms in the form of nanoclusters (NCs) rather than well-crystallized nanoparticles are evidenced by X-ray diffraction patterns, SEM images, and XPS spectra. The deposition of Ag nanoclusters on the surface of g-C₃N₄ nanosheets affect the crystal structure and slightly reduce the band gap energy of g-C₃N₄. The sharp decrease of photoluminescence intensity indicates that g-C₃N₄/Ag heterojunctions successfully prevent the recombination of photo-generated electrons and holes. The photocatalytic activities of as-synthesized photocatalysts are demonstrated through the degradation of rhodamine B (RhB) solutions under Xenon lamp irradiation. It is demonstrated that the photocatalytic activity depends strongly on the molar concentration of Ag⁺ in the starting solution. The g-C₃N₄/Ag heterojunctions prepared from 0.01 M of Ag⁺ starting solution exhibit the highest photocatalytic efficiency and allow 100% degradation of RhB after being exposed for 60 min under a Xenon lamp irradiation, which is four times faster than that of pure g-C₃N₄ nanosheets.

Effect of heating time on the structural, morphology, optical, and photocatalytic properties of graphitic carbon nitride (g-C₃N₄) nanosheets prepared at 550 °C in Ar atmosphere is studied. The investigations are carried out by using x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), UV–vis absorption, and photoluminescence (PL). At a heating temperature of 550 °C, g-C₃N₄ nanocrystals are formed after 0.5 h and become more orderly as the heating time increases. The surface area of the g-C₃N₄ nanosheets significantly increases as the preparation time increases. The g-C₃N₄ prepared in 2.5 h shows the highest photocatalytic performance, decomposing completely 10 ppm RhB solution under xenon lamp irradiation for 2.0 h.

This study demonstrates the influence of the Ag⁺/ PO 4 3 − ratio in precursor solution on the crystal structural formation, morphology, physical properties, and photocatalytic performance of a Ag₃PO₄ photocatalyst that is fabricated, using a facile precipitation method, from AgNO₃ and Na₂HPO₄⋅12H₂O. The material characterizations were carried out using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area, Fourier transform infrared (FTIR) absorption, Raman scattering, x-ray photoelectron spectroscopy (XPS), UV-vis absorption, and photoluminescence (PL). The results show that Ag₃PO₄ crystallizes better when the excess PO 4 3 − content increases, and the lattice parameters decrease slightly, while the crystal diameter and the particle size increase. This change is also observed in the Raman scattering and FTIR spectra with the increase in the vibration frequency of the [PO₄] group. The compression of the [PO₄] unit was also confirmed in the XPS spectra with the shift of P 2p peaks toward higher binding energy. The photocatalytic results showed that the samples synthesized from excess PO 4 3 − solution exhibited higher photocatalytic performance compared to the sample with a Ag⁺/ PO 4 3 − ratio of 3:1. A sample prepared from the precursor solution with a Ag⁺/ PO 4 3 − ratio of 3:1.5 was optimal for RhB decomposition under both visible light and natural sunlight, completely decomposing 10 ppm RhB after 15 minutes of xenon lamp irradiation and after 60 minutes under solar light irradiation. This is attributed to the high crystallinity, small particle size and low electron–hole recombination rate of the sample.