The Preparation Of S/P-doped Graphitic Carbon Nitride Nanosheets And Its Photocatalytic Activity

Photocatalytic technology is considered as one of the most promising strategies to solve environmental and energy problems faced by mankind because it has the characteristics of convenient operation,mild reaction conditions,greenness and economy.In recent years,graphitic carbon nitride?g-C3N4?was fascinating and a new type of visible light catalyst,but limited by photo-generated carriers easily combined,the limited light absorption range and other disadvantages.In this work,sulfur-doped graphitic carbon nitride nanosheets and porous phosphorus-doped graphitic carbon nitride nanosheets were successfully synthesized.A series of characterizations were used to study the physicochemical and optical properties of as-prepared photocatalysts.The photocatalytic activities of these photocatalysts was investigated by photocatalytic nitrogen fixation and photocatalytic degradation of antibiotic.The main experimental conclusions could be shown as follows:?1?Sulfur-doped graphitic carbon nitride nanosheets?SCNNS?were one-step directly obtained by collection of the gaseous thermal polymerization products of thiourea.According to the results of characterization,it was found that the basic structure of SCNNS was not been changed.The SCNNS showed a two-dimensional nanosheet structures with the thickness of 1.5nm and the larger surface area.In addition,the separation rate of photogenerated electron-hole pairs was improved.Compared with the bulk sulfur-doped graphitic carbon nitride?SCN?,the band structure of SCNNS has changed obviously.The valence band shifted down 0.12eV while the conduction band shifted up 0.1 OeV,so the oxidation and reduction activity of the SCNNS photocatalyst was stronger.The best photocatalytic activity of SCNNS was prepared at calcination temperature of 550? and the nitrogen fixation effect was 2.8 times of that of SCN.After four hours,the photodegradation of sulfathiazole and sulfamethazine by SCNNS reached 91.6%and 71.6%respectively.Besides,SCNNS showed high photocatalytic nitrogen fixation activity after 5 times of reuse.?2?Phosphorus-doped graphitic carbon nitride?PCN?was synthesized by simple impregnation-thermal polymerization using melamine and adenosine triphosphate as precursors and then further thermally exfoliation to prepared porous phosphorus-doped graphitic carbon nitride nanosheets?PCNS?.The photocatalytic activities of as-prepared photocatalysts was investigated by photocatalytic nitrogen fixation and degradation of sulfathiazole under visible light.According to the results of characterization,it was found that phosphorus-doped graphitic carbon nitride could expand the visible light response and improve the separation rate of photogenerated electron-hole pairs.The band structure of PCNS has changed obviously and the oxidation and reduction activity of it was stronger.The photocatalytic nitrogen fixation of 1:50 PCN?quality ratio?was the best and 3.9 times that of the original graphitic carbon nitride?CN?.Compared to the bulk CN and PCN,PCNS has a good degradation of sulfathiazole.The results also indicated that h+ and ·O2-were the main active species in the whole photocatalytic process and the photocatalytic removal efficiency of sulfathiazole would been reduced because of the presence of Cl^-,NO₃-and SO₄^2-.