Mechanistic Characteristics of Surface Modified Organic Semiconductor g-C3N4 Nanotubes Alloyed with Titania

Abstract

The visible-light-driven photocatalytic degradation of Bisphenol A (BPA) was investigated using the binary composite of alkaline treated g-C3N4 (HT-g-C3N4) deposited over commercial TiO2 (Evonik Degussa GmbH, Essen, Germany). The existence and contribution of both TiO2 and g-C3N4/HT-g-C3N4 in the composite was confirmed through various analytical techniques including powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (UV-vis-DRS), and photoluminescence (PL) analysis. The results showed that the titania in the binary composite exhibited both pure rutile and anatase phases. The morphological analysis indicated that the spongy “morel-like” structure of g-C3N4 turned to nanotube form after alkaline hydrothermal treatment and thereby decreased the specific surface area of HT-g-C3N4. The low surface area of HT-g-C3N4 dominates its promising optical property and effective charge transfer, resulting in a deprived degradation efficiency of BPA two times lower than pure g-C3N4. The binary composite of HT-g-C3N4/TiO2 exhibited excellent degradation efficiency of BPA with 2.16 times higher than the pure HT-g-C3N4. The enhanced photocatalytic activity was mainly due to the promising optical band gap structure with heterojunction interface, favorable specific surface area, and good charge separation.

Sugarcane juice derived carbon dot–graphitic carbon nitride composites for bisphenol A degradation under sunlight irradiation

“…This result suggests that CD/g-C 3 N 4 composites possess greater potential than that of pure g-C 3 N 4 to drive photocatalysis under the irradiation of the entire solar spectrum. In contrary to our earlier work that reported blue-shifted absorption spectra after titanium dioxide (TiO 2 ) loading [28] and acid treatment [29], the incorporation of CDs into g-C 3 N 4 consistently red-shifted the absorption spectra towards the visible and NIR region. However, the photocatalytic performance of the composites is possibly limited under NIR light irradiation because the UCPL properties of CDs (which could overcome the low energy of NIR-light photons to initiate the excitation of electrons) are not detected in Fig.…”

“…After incorporating the CDs, the CD/g-C 3 N 4 composites exhibited a more packed and agglomerated morphological nanostructure compared to that of pure g-C 3 N 4 . A similar observation was reported in our previous research [28], showing that the clustered effect was attributed to the self-assembly process during the hydrothermal treatment [43]. However, a more porous structure in the CD/g-C 3 N 4 (0.5) composite was observed as compared to that of CD/g-C 3 N 4 (0.1), signifying that the increasing concentration of CDs could reduce the agglomeration effect in the composites.…”

“…3, the pure g-C 3 N 4 showed expected absorption peaks at 265 nm and 340 nm due to the π–π* or n–π* electronic transitions in the conjugated aromatic s-heptazine ring system of g-C 3 N 4 [63]. The onset of the absorption spectra of pure g-C 3 N 4 started from 452 nm, showing a band gap of 2.75 eV, which is almost the same as that previously reported [28,46,64]. It is obvious that all CD/g-C 3 N 4 composites displayed a broad light absorption in the whole solar spectrum ranging from 200 to 800 nm due to the quantum confinement effect induced by the CDs [65].…”

“…It is well-known that the organic semiconductor g-C 3 N 4 possesses visible light harvesting properties due to its narrow band gap energy (≈2.7 eV) [15]. Thus g-C 3 N 4 has emerged as a promising polymeric semiconductor for photocatalytic reduction of carbon dioxide (CO 2 ) [16–20], hydrogen evolution [21–25], oxidation of NO [26–27], and degradation of pollutants [28–30]. However, the photocatalytic performance of bulk g-C 3 N 4 remains unsatisfactory because of the fast recombination rate of electron pairs and narrower light absorption range over the entire solar spectrum.…”

“…Turning g-C 3 N 4 into a mesoporous nanorod structure [31] and the hydrogenation of g-C 3 N 4 [32] could be an alternative to increase the light-harvesting ability and charge separation efficiency. Our group has reported the self-modification of g-C 3 N 4 structures using alkaline [28] and acid treatment [29] to overcome the limitations of g-C 3 N 4 . Despite of the positive results, the self-modification consumes concentrated alkali and acid, which is harmful to our environment and health.…”