Preparation of high-crystalline and non-metal modified g-C₃N₄ for improving ultrasound-accelerated...

As a non-metallic organic semiconductor, graphitic carbon nitride (g-C₃N₄) has received much attention due to its unique physicochemical properties. However, the photocatalytic activity of this semiconductor faces challenges due to factors such as low electronic conductivity and limited active sites provided on its surface. The morphology and structure of g-C₃N₄, including macro/micro morphology, crystal structure and electronic structure can affect its catalytic activity. Non-metallic heteroatom doping is considered as an effective method to tune the optical, electronic and other physicochemical properties of g-C₃N₄. Here, we synthesized non-metal-doped highly crystalline g-C₃N₄ by one-pot calcination method, which enhanced the photocatalytic activity of g-C₃N₄ such as mesoporous nature, reduced band gap, wide-range photousability, improved charge carrier recombination, and the electrical conductivity was improved. Hence, the use of low-power white-LED-light illumination (λ ≥ 420 nm) and ultrasound (US) irradiation synergistically engendered the Methylene Blue (MB) mineralization efficiency elevated to 100% within 120 min by following the pseudo-first-order mechanism under the following condition (i.e., pH 11, 0.75 g L^-1 of O-doped g-C₃N₄ and S-doped g-C₃N₄, 20 mg L^-1 MB, 0.25 ml s^-1 O₂, and spontaneous raising temperature). In addition, the rapid removal of MB by sonophotocatalysis was 4 times higher than that of primary photocatalysis. And radical scavenging experiments showed that the maximum distribution of active species corresponds to superoxide radical [Formula: see text]. More importantly, the sonophotocatalytic degradation ability of O-doped g-C₃N₄ and S-doped g-C₃N₄ was remarkably sustained even after the sixth consecutive run.