Abstract:

Composite materials of pitch-derived activated carbon-supported nitrogen-rich graphitic carbon nitride （PAC/g-C₃N₅） were prepared by impregnation and high-temperature thermal polymerization. One of these composites was systematically characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR）, N₂ adsorption-desorption, UV-vis diffuse reflectance spectroscopy （UV-vis DRS）, photoluminescence spectroscopy （PL） and electrochemical impedance spectroscopy （EIS）. The photocatalytic degradation of methylene blue （MB） dye by the composite material was studied. The results showed that the specific surface area was 479.1 m²/g after loading g-C₃N₅ onto the high specific surface area PAC as the support. PAC hindered the layered stacking of g-C₃N₅, expanded the π-π^* electron delocalization, effectively inhibited the photoelectron-hole recombination, promoted the separation of photogenerated carriers, and thus improved the photocatalytic performance. After dark adsorption for 60 min and simulated sunlight irradiation for 120 min, the degradation percentage of MB dye by 3% PAC/g-C₃N₅ composite reached 97.62%. Good photocatalytic performance was still maintained after 5 cycles. The results of active species capture experiment showed that superoxide radical （·O₂^-） was the main active species in photocatalytic reaction. The mechanism in photocatalytic degradation of MB by PAC/g-C₃N₅ was proposed based on energy band structure and energy band potential.

Key words: nitrogen-rich carbon nitride, pitch-derived activated carbon, composite material, photocatalysis, methylene blue