Facile fabrication of novel SiO2/g-C3N4 core-shell nanosphere photocatalysts with enhanced visible light activity

Novel SiO2/g-C3N4 core-shell nanospheres were simply synthesized using heating method to anneal the mixture of silica dioxide nanospheres and molten cyanamide (CA) in nitrogen atmosphere. The effects of various initial mass ratios of SiO2 nanospheres and CA molecules on the catalyst structure, surface property and catalytic activity have been systematically investigated. The characterization results show that the as-obtained photocatalysts possess the ordered core-shell nanostructure, large mesoporous distribution and inflated BET specific surface areas. The photocatalytic activities of the SiO2/g-C3N4 composites were evaluated by decomposing the rhodamine B (RhB) dye under visible light irradiation. Compared with pure g-C3N4, all of the SiO2/g-C3N4 core-shell composites showed the improved photoactivity, and the optimal SiO2/g-C3N4 catalyst (SC-3) showed the highest activity with an RhB conversion of 94.3% after 150 min visible light irradiation, which is 3.5 times higher than that of pure g-C3N4. Meanwhile, the recycling test showed that the SC-3 sample owns outstanding stability and durability. The enhancement in both activity and stability can be assigned to the specific core-shell structure, inflated surface area, higher visible light adsorption and efficient charge separation originating from the closely contacted interfaces between SiO2 nanospheres and g-C3N4.