Effect of Oxygen on Photocatalytic Nitrogen Fixation Performance of N Vacancy-embedded Graphitic Carbon Nitride

N vacancy and oxygen co-doped g-C3N4 with outstanding N-2 photofixation ability was synthesized by dielectric barrier discharge plasma treatment. XRD , UV-Vis, N-2 adsorption, SEM , XPS , PL and TPD were used to characterize the as-prepared catalysts. The result shows that plasma treatment does not change the morphology of as-prepared catalyst but introduce nitrogen vacancies and oxygen into g-C3N4 lattice simultaneously. The as-prepared co-doped g-C3N4 displays the ammonium ion production rate as high as 5.9 mg . L-1 . h(-1) . g(cat)(-1) which is 2.2 and 20 times that of individual N vacancy-doped g-C3N4 and neat g-C3N4, as well as good catalytic stability. Experimental and density functional theory( DFT) calculation results indicate that, compared with individual N vacancies doping, the introduction of oxygen can promote the activation ability of N vacancies to N-2 molecule, leading to the promoted N-2 photofixation performance.