Oxalic acid induced defect state graphitic carbon nitride with improved photocatalytic performance

A defect state g-C 3 N 4 was synthesized from urea by thermal condensation and oxalic acid treatment. Various analytical methods such as X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy were adopted to characterize the structures and properties of g-C 3 N 4 . The results showed that oxygen atoms replaced the carbon atoms of g-C 3 N 4 , which changed the band structure of g-C 3 N 4 . The catalytic performances of defect state g-C 3 N 4 were improved and exhibited better photocatalytic activity than pure g-C 3 N 4 . For the effects of acetic acid concentration, g-C 3 N 4 treated by 0.05 mol/L oxalic acid exhibited enhanced photocatalytic performance, which could be attributed to the suitable defect concentration. The photocatalytic degradation mechanism was proposed. Superoxide radicals instead of hydroxyl radicals played an important role in the rhodamine B degradation.