Efficient Advanced Oxidation Process (AOP) for Photocatalytic Contaminant Degradation Using Exfoliated Metal-Free Graphitic Carbon Nitride and Visible Light-Emitting Diodes

Abstract

The photocatalytic performance of metal-free graphitic carbon nitride (g-C3N4) was examined using visible light-emitting diodes (LEDs). A comparative and parametric study was conducted using the photocatalytic degradation of phenol as a model reaction. The g-C3N4 photocatalyst was synthesized from melamine using thermal condensation, followed by a thermal exfoliation that increases the catalyst surface area from 11 to 170 m2/g. Different characterization techniques, namely X-ray powder diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption using the Brunauer–Emmett–Teller method, ultraviolet-visible (UV–vis) spectroscopy, transmission electron microscopy, photoluminescence spectroscopy (PL), and zeta potential analysis, were used to characterize the photocatalyst. A comparison of the photodegradation experiments conducted with a full-spectrum xenon lamp and a custom-made single-wavelength LED immersion lamp showed that the photocatalyst performance was better with the LED immersion lamp. Furthermore, a comparison of the performance of exfoliated and bulk g-C3N4 revealed that exfoliated g-C3N4 completely degraded the pollutant in 90 min, whereas only 25% was degraded with bulk g-C3N4 in 180 min because the exfoliated g-C3N4 enhances the availability of active sites, which promotes the degradation of phenol. Experiments conducted at different pH have shown that acidic pH favors the degradation process. The exfoliated g-C3N4 has shown high photocatalytic performance in the photodegradation of other phenolic compounds, such as catechol, m-cresol, and xylenol, as well.

Synthesis of Highly Active Doped Graphitic Carbon Nitride using Acid‐Functionalized Precursors for Efficient Adsorption and Photodegradation of Endocrine‐Disrupting Compounds

“…The C 1s and N 1s XPS spectra were recorded to investigate the interaction between C and N atoms. The deconvoluted C 1s XPS spectra of the doped samples (Figure 2a) exhibited two strong peaks appearing at 285 and 288 eV, which can be assigned to the standard (C−C) carbon bonds and sp 2 hybridized carbon (N−C=N) in triazine rings [11,18] . Two low‐intensity peaks observed at 286 and 289 eV can be assigned to the amino‐functional groups (C−NH 2 ) and the carboxyl group (O−C=O) bound to the surface of g‐C 3 N 4 , respectively [11,18a,19] .…”

“…The deconvoluted C 1s XPS spectra of the doped samples (Figure 2a) exhibited two strong peaks appearing at 285 and 288 eV, which can be assigned to the standard (C−C) carbon bonds and sp 2 hybridized carbon (N−C=N) in triazine rings [11,18] . Two low‐intensity peaks observed at 286 and 289 eV can be assigned to the amino‐functional groups (C−NH 2 ) and the carboxyl group (O−C=O) bound to the surface of g‐C 3 N 4 , respectively [11,18a,19] . In the case of PBCN, the intensities of C 1s peaks were substantially lower than their counterparts observed for SBCN and OBCN, which indicates that the C atoms might have been replaced by P atoms in the chemical structure of g‐C 3 N 4 [20] .…”

“…The strong peak at 397.8 eV corresponds to the triazine rings′ sp 2 hybridized nitrogen atom bound to carbon (C−N=C). The other two peaks of medium intensity appearing at 400.2 and 401.2 eV can be assigned to the presence of tertiary N in N−(C) 3 units and amino functional groups (NH 2 or NH), respectively [11,18,20] …”

“…Although a wide variety of catalytic materials exist that can be used in photocatalysis, graphitic carbon nitride (g‐C 3 N 4 ) has emerged as one of the most promising materials for photocatalytic applications in both environmental and energy‐producing processes [10] . g‐C 3 N 4 is a non‐toxic polymeric semiconductor exhibiting high chemical and thermal stability [11] . This semiconductor can easily be synthesized from compounds such as melamine and urea via the thermal decomposition of nitrogen‐rich precursors under appropriate reaction conditions.…”

“…This semiconductor can easily be synthesized from compounds such as melamine and urea via the thermal decomposition of nitrogen‐rich precursors under appropriate reaction conditions. The main drawback of g‐C 3 N 4 is its limited photocatalytic activity resulting from its low surface area [11] . Some techniques like exfoliation improve the surface area and performance but need additional heat.…”