Construction of SiO2-TiO2/g-C3N4 composite photocatalyst for hydrogen production and pollutant degradation: Insight into the effect of SiO2

Using low-cost precipitated silica (SiO 2 ) as the carrier, a ternary SiO 2 -TiO 2 /g-C 3 N 4 composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process. The as-prepared composite exhibits photocatalytic hydrogen production and pollutant degradation performance under solar-like irradiation. The effect of SiO 2 carrier on the properties of the heterostructure between TiO 2 and g-C 3 N 4 (CN) was systematically studied. It is found that SiO 2 has important effects on promoting the interaction between TiO 2 and CN. The particle size of TiO 2 and CN was obviously reduced during the calcination process due to the effects of SiO 2 . Especially, the TiO 2 particles exhibit monodispersed state with particle size below 10 nm (quantum dots), resulting in the improvement of the contact area and the interaction between TiO 2 and CN, and leading to the formation of efficient TiO 2 /CN Z-scheme heterostructure in SiO 2 -TiO 2 /CN. Besides, the introduction of SiO 2 can increase the specific surface area and light absorption of SiO 2 -TiO 2 /CN, further promoting the photocatalytic reaction. As expected, the optimum SiO 2 -TiO 2 /CN composite exhibits 12.3, 3.1 and 2.9 times higher photocatalytic hydrogen production rate than that of SiO 2 -TiO 2 , CN and TiO 2 /CN under solar-like irradiation, while the photocatalytic active component in SiO 2 -TiO 2 /CN is only about 60 wt%. Moreover, the rhodamine B degradation rate of SiO 2 -TiO 2 /CN is also higher than that of SiO 2 -TiO 2 , CN and TiO 2 /CN.