Herein, we demonstrate the synthesis of highly efficient Fe-doped graphitic carbon nitride (g-C₃N₄) nanosheets via a facile and cost effective method. The synthesized Fe-doped g-C₃N₄ nanosheets were well characterized by various analytical techniques. The results revealed that the Fe exists mainly in the +3 oxidation state in the Fe-doped g-C₃N₄ nanosheets. Fe doping of g-C₃N₄ nanosheets has a great influence on the electronic and optical properties. The diffuse reflectance spectra of Fe-doped g-C₃N₄ nanosheets exhibit red shift and increased absorption in the visible light range, which is highly beneficial for absorbing the visible light in the solar spectrum. More significantly, the Fe-doped g-C₃N₄ nanosheets exhibit greatly enhanced photocatalytic activity for the degradation of Rhodamine B under sunlight irradiation. The photocatalytic activity of 2 mol% Fe-doped g-C₃N₄ nanosheets is almost 7 times higher than that of bulk g-C₃N₄ and 4.5 times higher than that of pure g-C₃N₄ nanosheets. A proposed mechanism for the enhanced photocatalytic activity of Fe-doped g-C₃N₄ nanosheets was investigated by trapping experiments. The synthesized photocatalysts are highly stable even after five successive experimental runs. The enhanced photocatalytic performance of Fe-doped g-C₃N₄ nanosheets is due to high visible light response, large surface area, high charge separation and charge transfer. Therefore, the Fe-doped g-C₃N₄ photocatalyst is a promising candidate for energy conversion and environmental remediation.

A facile and reproducible template free in situ precipitation method has been developed for the synthesis of Ag₃PO₄ nanoparticles on the surface of a g-C₃N₄ photocatalyst at room temperature. The g-C₃N₄–Ag₃PO₄ organic–inorganic hybrid nanocomposite photocatalysts were characterized by various techniques. TEM results show the in situ growth of finely distributed Ag₃PO₄ nanoparticles on the surface of the g-C₃N₄ sheet. The optimum photocatalytic activity of g-C₃N₄–Ag₃PO₄ at 25 wt% of g-C₃N₄ under visible light is almost 5 and 3.5 times higher than pure g-C₃N₄ and Ag₃PO₄ respectively. More attractively, the stability of Ag₃PO₄ was improved due to the in situ deposition of Ag₃PO₄ nanoparticles on the surface of the g-C₃N₄ sheet. The improved performance of the g-C₃N₄–Ag₃PO₄ hybrid nanocomposite photocatalysts under visible light irradiation was induced by a synergistic effect, including high charge separation efficiency of the photoinduced electron–hole pair, the smaller particle size, relatively high surface area and the energy band structure. Interestingly, the heterostructured g-C₃N₄–Ag₃PO₄ nanocomposite significantly reduces the use of the noble metal silver, thereby effectively reducing the cost of the Ag₃PO₄ based photocatalyst.

N-doped ZnO/g-C₃N₄ hybrid core–shell nanoplates have been successfully prepared via a facile, cost-effective and eco-friendly ultrasonic dispersion method for the first time. HRTEM studies confirm the formation of the N-doped ZnO/g-C₃N₄ hybrid core–shell nanoplates with an average diameter of 50 nm and the g-C₃N₄ shell thickness can be tuned by varying the content of loaded g-C₃N₄. The direct contact of the N-doped ZnO surface and g-C₃N₄ shell without any adhesive interlayer introduced a new carbon energy level in the N-doped ZnO band gap and thereby effectively lowered the band gap energy. Consequently, the as-prepared hybrid core–shell nanoplates showed a greatly enhanced visible-light photocatalysis for the degradation of Rhodamine B compare to that of pure N-doped ZnO surface and g-C₃N₄. Based on the experimental results, a proposed mechanism for the N-doped ZnO/g-C₃N₄ photocatalyst was discussed. Interestingly, the hybrid core–shell nanoplates possess high photostability. The improved photocatalytic performance is due to a synergistic effect at the interface of the N-doped ZnO and g-C₃N₄ including large surface-exposure area, energy band structure and enhanced charge-separation properties. Significantly, the enhanced performance also demonstrates the importance of evaluating new core–shell composite photocatalysts with g-C₃N₄ as shell material.