Plasma-exfoliated g-C3N4 with oxygen doping: tailoring photocatalytic properties

Heteroatom doping and defect engineering have been proposed as effective ways to modulate the energy band structure and improve the photocatalytic activity of g-C3N4. In this work, ultrathin defective g-C3N4 was successfully prepared using cold plasma. Plasma exfoliation reduces the thickness of g-C3N4 from 10 nm to 3 nm, while simultaneously introducing a large number of nitrogen defects and oxygen atoms into g-C3N4. The amount of doped O was regulated by varying the time and power of the plasma treatment. Due to N vacancies, O atoms formed strong bonds with C atoms, resulting in O doping in g-C3N4. The mechanism of plasma treatment involves oxygen etching and gas expansion. Photocatalytic experiments demonstrated that appropriate amount of O doping improved the photocatalytic degradation of rhodamine B compared with pure g-C3N4. The introduction of O optimized the energy band structure and photoelectric properties of g-C3N4. Active species trapping experiments revealed <middle dot>O-2(-) as the main active species during the degradation.