Synthesis and photocatalytic activity of SiO2/g-C3N4 composite photocatalyst

• Novel SiO2/g-C3N4 composite was synthesized by a simple mixing-calcination method.
• The SiO2/g-C3N4 composite degraded RhB 2.5× faster than g-C3N4 under visible light.
• The origin of the increased photoactivity was discussed.
• The addition of SiO2 decreased the aggregation of g-C3N4 stack layers.

A visible-light driven SiO2/g–C3N4 composite was prepared by heating a mixture of SiO2 and melamine. The products were characterized by X-ray diffraction, Brunauer–Emmett–Teller analysis, transmission electron microscopy, and ultraviolet–visible diffuse reflectance spectroscopy. Results indicate that the composite only contained SiO2 and g-C3N4. The addition of SiO2 had minimal influence on light absorption, but the specific surface area was increased. In addition, the aggregation of g-C3N4 in the SiO2/g-C3N4 composite was weakened. The increased surface area and decreased aggregation of g-C3N4 are considered as the cause of the strong activity of the SiO2/g-C3N4 composite in RhB photodegradation.