Promotion of activation ability of N vacancies to N2 molecules on sulfur-doped graphitic carbon nitride with outstanding photocatalytic nitrogen fixation ability

Abstract Nitrogen vacancies and sulfur co-doped g-C 3 N 4 with outstanding N 2 photofixation ability was synthesized via dielectric barrier discharge plasma treatment. X-ray diffraction, ultraviolet–visible spectroscopy, N 2 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-C 3 N 4 lattice simultaneously. The as-prepared co-doped g-C 3 N 4 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-C 3 N 4 and neat g-C 3 N 4 , 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 N 2 molecules, leading to promoted N 2 photofixation performance.