Photocatalytic decontamination of toxic hexavalent chromium in water over graphitic carbon nitride supported sulfur nanoparticles

Abstract

Abstract We report here for the first time a facile strategy for the preparation of graphitic carbon nitride ( gCN ) composited with different weight percentages of sulfur ( SNPs ) nanoparticles ( SCN - x ), and their remarkable photocatalytic decontamination of toxic hexavalent chromium. Fabrication of the binary hybrid photocatalysts were carried out via two facile steps: conventional thermal polycondensation of melamine into bulk gCN and its delamination, followed by disproportionation of thiosulfate to produce fine SNPs dispersed on gCN in the presence of weak organic acids. Absorption intensity of gCN was markedly expanded into visible region after composition with sulfur nanoparticles. Photocatalytic reduction efficiency of Cr ( VI ) by SCN - x was remarkably higher than bare gCN ; and the optimum SNPs content on gCN was 8.7 wt% ( SCN - 2 ) with photoreduction efficiency of ca. 99 % after 15 min of visible light illumination. Electrochemical characterizations of SNP and SCN - 2 samples indicated that the glassy carbon electrode (GCE) modified with SCN - 2 enhanced formation of Cr(III) at 65.4 % compared to SNP-modified electrode at ∼36 %. BET results indicated that the presence of sulfur nanoparticles on gCN resulted in higher surface areas (influencing catalytic active sites that improve visible-light absorption), thus, facilitating electron transfer from the conduction band to sulfur species, whilst preventing the electron from recombining with holes. This work opens up the importance of sulfur utilization as promoter for photocatalytic applications.