Abstract: Nitrogen vacancies and sulfur co-doped g-C₃N₄ with outstanding N₂ photofixation ability was synthesized via dielectric barrier discharge plasma treatment. X-ray diffraction, ultraviolet-visible spectroscopy, N₂ adsorption, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and temperature-programmed desorption were used to characterize the as-prepared catalyst. The results showed that plasma treatment cannot change the morphology of the as-prepared catalyst but introduces nitrogen vacancies and sulfur into g-C₃N₄ lattice simultaneously. The as-prepared co-doped g-C₃N₄ displays an ammonium ion production rate as high as 6.2 mg·L^-1·h^-1·g_cat^-1, which is 2.3 and 25.8 times higher than that of individual N-vacancy-doped g-C₃N₄ and neat g-C₃N₄, respectively, as well as showing good catalytic stability. Experimental and density functional theory calculation results indicate that, compared with individual N vacancy doping, the introduction of sulfur can promote the activation ability of N vacancies to N₂ molecules, leading to promoted N₂ photofixation performance.

Key words: Graphitic carbon nitride, Nitrogen photofixation, Co-doping, Photocatalysis, Plasma treatment