Hydroxyl-Rich Porous Silica Nanosheets Decorated with Oxygen-Doped Carbon Nitride Nanoparticles for Photocatalytic Degradation of Rhodamine B

Introduction of hydroxyl-rich porous silica nanosheets (SiNSs) induced the high dispersion of oxygen-doped carbon nitride (OCN) nanoparticles via hydroxyl- and mesopore-dual-confined thermal polymerization of precursor melamine and simultaneous hydroxyl-induced O-doping by replacing the edge N atoms of heptazine. The resultant OCN/SiNS composites possessed enhanced photocatalytic activity for Rhodamine B (RhB) oxidation compared to bulk CN, with a quick reaction within 55 min and an apparent rate constant of 0.073 min–1, mainly owing to the high adsorption of SiNSs, larger specific surface area of highly dispersed OCN nanoparticles, and the adjusted band structure originated from the comprehensive effects of nanoparticle structure and O-doping, which led to a narrowed band gap with strengthened visible-light adsorption and an enhanced photogenerated carrier separation efficiency. Furthermore, in terms of the photocatalytic mechanism, it showed a more reactive oxygen species of singlet oxygen (main) and superoxide radicals (secondary) for effective RhB decomposition, but significantly lowered the oxidative ability of the holes towards RhB. This work suggests the great potential of silica nanosheets as a supporter and inducer in dispersion and structure tuning of carbon nitride for enhanced photocatalytic property.