Highly efficient noble metal-free g-C3N4@NixSy nanocomposites for catalytic reduction of nitrophenol, azo dyes and Cr(VI)

g-C3N4@NixSy nanocomposite have been prepared by a simple pyrolysis under different temperature, in which the g-C3N4@Ni3S2_700 nanocomposite present an efficient catalyst for the removal of the nitrophenol, azo dyes and Cr(VI). This method offers a new strategy to fabricate novel g-C3N4@NixSy catalysts for pollutant treatment. [Display omitted] •Noble metal-free g-C3N4@NixSy nanocomposite as catalyst has been fabricated.•It presents high catalytic activity to remove nitrophenol and azo dye in solution.•It also has high catalytic reduction activity to reduce Cr(VI) to Cr(III). g-C3N4@NixSy nanocomposites have been prepared by a simple and efficient one-step pyrolysis technique under different temperatures. Furthermore, the synthesized catalysts were extensively characterized through X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), Raman, Field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyses. Experiments revealed that the g-C3N4@Ni3S2_700 nanocomposite exhibits significant catalytic performance and is an effective catalyst for removing 4-nitrophenol (4-NP), 3-nitrophenol (3-NP), 2-nitrophenol (2-NP), 2,4,6-trinitrophenol (2, 4, 6-TNP), Rhodamine B (RhB), Methyl orange (MO), Congo red (CR), Methylene blue (MB), Azure I, Origin IV and Cr(VI). The as-prepared g-C3N4@Ni3S2_700 displayed NaBH4 induced reduction of 4-NP to 4-AP with 100% reduction achieved within 3 min with an apparent rate constant (kapp) of 1.17 min−1. Because of its high activity, convenient preparation, low cost, easy operation and high universality, it is expected to play a great practical application potential in the removal of wastewater pollutants and catalysis.