Synthesis of sulfur doped C_(3)N_(4) with enhanced photocatalytic activity in molten salt

In this paper,sulfur doped g-C_(3)N_(4)(S-g-C_(3)N_(4))was successfully prepared at 500℃ for 3 h via a modified molten salt method using dicyandiamide as the main raw material,trithiocyanuric acid as the sulfur source and LiBreKCl as the reaction medium.The as-prepared SeCN5.0% sample(the mass ratio of trithiocyanuric acid to dicyandiamide was 5.0%)composed of irregular flakes showed a band gap of 1.83 eV,which was narrower than that(2.55 eV)of pristine g-C_(3)N_(4).The SeCN5.0% sample also exhibited an outstanding absorption capacity of visible light.Moreover,the photodegradation rate toward methylene blue and tetracycline were respectively 10 and 20 times as high as that of bulk g-C_(3)N_(4) prepared by conventional heating methods,confirming its superior photocatalytic performance.These results can be attributed to that the replacement of lattice nitrogen with sulfur atom tuned the electronic structure of g-C_(3)N_(4),improved the absorption of visible light,optimized the separation of photogenerated electron-hole pairs,and consequently enhanced the photocatalytic activity of g-C_(3)N_(4).Moreover,the trapping experiments implied that hole(ht)and superoxide radical($O2)were the main active species in the process of photodegradation.