In situ preparation of g-C3N4/bismuth-based oxide nanocomposites with enhanced photocatalytic activity

• g-C3N4/Bi2O2CO3 and g-C3N4/BiOCl were prepared by an in situ calcination method.
• Precursor of g-C3N4 has a significant effect on the composite’s structure.
• Intimately contacted interfaces facilitated charge separation and transfer.
• Composites showed enhanced activity for DBP and MO degradation under visible light.

Different mass percents of g-C3N4/Bi2O2CO3 and g-C3N4/BiOCl nanocomposites with intimately contacted interfaces were synthesized in situ by mixing Bi2O3 nanoparticles with melamine or guanidine hydrochloride and calcinating at 550 °C for 3 h. The fabricated nanocomposites were well-characterized by various analytical techniques. The results showed that the Bi2O2CO3 and BiOCl nanosheets grow out from the g-C3N4 bulk, producing closely contacted interfaces between the Bi oxide component and the g-C3N4 component. The UV–vis diffuse reflectance spectra of g-C3N4/Bi2O2CO3 and g-C3N4/BiOCl nanocomposites exhibited increased visible light absorption compared to g-C3N4 and Bi2O3 separately. Moreover, the nanocomposites showed significantly enhanced photocatalytic activity for the degradation of dibutyl phthalate and methyl orange under visible light. A proposed photocatalytic mechanism for the enhanced photoactivity of nanocomposites was investigated by scavenging experiments and fluorescent spectroscopy. The increased photocatalytic activity is mainly attributed to the effective separation and transfer of photo-induced carriers in the intimate contact between g-C3N4 and Bi2O2CO3 or BiOCl. The results showed that the different precursors of g-C3N4 have a significant effect on the composite's structure; i.e., Bi2O3 can react to form different bismuth-based oxides depending on the different precursors used to generate g-C3N4. This work demonstrates a convenient way to fabricate visible light responsive materials with potential for environmental remediation.

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