Magnetically recyclable magnetic biochar graphitic carbon nitride nanoarchitectures for highly efficient charge separation and stable photocatalytic activity under visible-light irradiation

The demand for developing low-cost photocatalyst that is easily separable for re-using to replace the noble metal-based photocatalysts. Herein, for the first time, we develop an innovative magnetic biochar (M-BC) based graphitic carbon nitride (g-CN) catalyst with well-designed nanoarchitectures (M-BC@g-CN) by in situ hydrothermal reaction and pyrolysis. As a photocatalyst, M-BC@g-CN catalyst delivers highly efficient and stable photocatalytic degradation for RhB dye, which is better than those of M-BC and g-C3N4 nanosheets. The rate constant (k) of M-BC@g-CN is 2.62 × 10−2 which is ~2.74 times higher than that of g-C3N4 (0.70 × 10−2 min−1). In addition, M-BC@g-CN shows a strong ferromagnetic behavior originated from Fe2O3, which can be used for rapid separation of catalyst from aqueous solution by a magnet and re-used again after the photocatalytic reaction, suggesting its outstanding eco-friendliness and recyclability. Magnetically recyclable M-BC@g-CN is also efficient for electron-hole charge separation and effectively suppresses the recombination of electron-hole pair to enhance its photocatalytic activity. Moreover, the photocatalytic mechanism of *OH and *O2− reactive species for degradation of RhB dye is revealed by the ESR measurements.