Improved solar light stimulated charge separation of g-C 3 N 4  through self-altering acidic treatment

Leong, Kah Hon; Lim, Ping Feng; Sim, Lan Ching; Punia, Varun; Saravanan, Pichiah

doi:10.1016/j.apsusc.2017.06.169

Cited by 33 publications

(11 citation statements)

References 43 publications

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“…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.…”

Section: Resultscontrasting

confidence: 99%

“…Unlike CDs, TiO 2 in combination with g-C 3 N 4 for the photocatalytic process [28] was able to trap electrons efficiently due to the favorable band edge potential; however, the material could not absorb visible light. As shown in Table S2 (Supporting Information File 1), CD/g-C 3 N 4 composites demonstrated the best degradation efficiency of BPA than that of other composites reported earlier in our previous works [28–29]. …”

Section: Resultsmentioning

confidence: 59%

“…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.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Sim

Wong

Hak

et al. 2018

Beilstein J. Nanotechnol.

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Carbon dots (CDs) and graphitic carbon nitride (g-C3N4) composites (CD/g-C3N4) were successfully synthesized by a hydrothermal method using urea and sugarcane juice as starting materials. The chemical composition, morphological structure and optical properties of the composites and CDs were characterized using various spectroscopic techniques as well as transmission electron microscopy. X-ray photoelectron spectroscopy (XPS) results revealed new signals for carbonyl and carboxyl groups originating from the CDs in CD/g-C3N4 composites while X-ray diffraction (XRD) results showed distortion of the host matrix after incorporating CDs into g-C3N4. Both analyses signified the interaction between g-C3N4 and CDs. The photoluminescence (PL) analysis indicated that the presence of too many CDs will create trap states at the CD/g-C3N4 interface, decelerating the electron (e−) transport. However, the CD/g-C3N4(0.5) composite with the highest coverage of CDs still achieved the best bisphenol A (BPA) degradation rate at 3.87 times higher than that of g-C3N4. Hence, the charge separation efficiency should not be one of the main factors responsible for the enhancement of the photocatalytic activity of CD/g-C3N4. Instead, the light absorption capability was the dominant factor since the photoreactivity correlated well with the ultraviolet–visible diffuse reflectance spectra (UV–vis DRS) results. Although the CDs did not display upconversion photoluminescence (UCPL) properties, the π-conjugated CDs served as a photosensitizer (like organic dyes) to sensitize g-C3N4 and injected electrons to the conduction band (CB) of g-C3N4, resulting in the extended absorption spectrum from the visible to the near-infrared (NIR) region. This extended spectral absorption allows for the generation of more electrons for the enhancement of BPA degradation. It was determined that the reactive radical species responsible for the photocatalytic activity were the superoxide anion radical (O2 •−) and holes (h+) after performing multiple scavenging tests.

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Section: Resultscontrasting

confidence: 99%

Section: Resultsmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Sim

Wong

Hak

et al. 2018

Beilstein J. Nanotechnol.

Self Cite

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“…The isosurface distribution of a HOMO consists of the contribution from the non‐bonding state of the nitrogen atom facing the structural holes, while a LUMO is represented by the π‐conjugated sp 2 C=N bond. Hence the transition is mainly from a lone pair of the nitrogen atom to the sp 2 C=N orbitals ,. Remarkably, the H−L spatial position varies with the size of the CNQD, where we can see a better H−L separation for the larger structure C45 that is otherwise absent in the smaller QDs.…”

Section: Resultsmentioning

confidence: 74%

Mechanism of Charge Separation and Frontier Orbital Structure in Graphitic Carbon Nitride and Graphene Quantum Dots

2018

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Graphene quantum dots (GQDs) and carbon nitride quantum dots (CNQDs), the latest addition to the carbon material family, are promising materials for numerous novel applications in optical sensing, photocatalysis, biosensing, and photovoltaics. However, understanding the photocatalytic capability of CNQDs compared to GQDs requires investigations of the charge behavior on the excited state energy surface. In this work, through time-dependent density functional tight binding (TD-DFTB) calculations, we show that CNQDs exhibit superior ground state frontier orbitals (FOs) localization. Strong localization of the FOs and excited state charge separation observed in the first excited state are caused by the relaxation of the structure. Excited energy surface investigations reveal spatial confinement of FOs to the stretched C-N bonds due to excited state structural relaxation. On the other hand, no such localized FOs structure was found for GQDs, presumably caused by its strong π-conjugated configuration not allowing large structural changes upon excitation. The optical absorption and emission of CNQDs is sensitive to size and does not show large variations with the shape of the QD. Our approach provides an explanation for the origin of the enhanced photocatalytic performance of CNQDs over GQDs and their characteristic FOs localization.

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“…Peaks in the high-resolution of the N1s and Fe2p spectra were attributed to molecular components. The N1s spectrum of g-C 3 N 4 in Figure 2e contains four peaks that were attributed to pyridinic N (395.3 and 397.6 eV) [29], C-N (396.6 eV), and C=N-C (401.1 eV), respectively [30]. Fe-doping added peaks at 397.…”

Section: Degradation Performance Of the Catalystsmentioning

confidence: 99%

Facile Production of a Fenton-Like Photocatalyst by Two-Step Calcination with a Broad pH Adaptability

Yang

et al. 2020

Nanomaterials

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A novel heterogeneous Fenton-like photocatalyst, Fe-doped graphitic carbon nitride (Fe-g-C3N4), was produced by facile two-step calcination method. This Fe–g–C3N4 catalyzed rhodamine B degradation in the presence of H2O2 accompanied with visible light irradiation. transmission electron microscopy(TEM), x-ray diffraction (XRD), FT-IR, x-ray photoelectron spectroscopy (XPS), and photoluminescence fluorescent spectrometer (PL) characterization analysis methods were adopted to evaluate the physicochemical property of samples. It can be observed that the Fe-g-C3N4 exhibited excellent photocatalytic Fenton-like activity at a wide pH range of 3–9, with rhodamine B(RhB) degradation efficiency up to 95.5% after irradiation for 45 min in the presence of 1.0 mM H2O2. Its high activity was ascribed to the formation of Fe–N ligands in the triazine rings that accelerated electron movement driving the Fe(III)/Fe(II) redox cycle, and inhibited photo-generated electron hole re-combinations for continuous generation of reactive oxygen species by reactions between Fe(II) and H2O2. The main active oxygen species were hydroxyl radicals, followed by superoxide radicals and hole electrons. This produced catalyst of Fe–g–C3N4 shows excellent reusability and stability, and can be a promising candidate for decontamination of wastewater.

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Improved solar light stimulated charge separation of g-C 3 N 4 through self-altering acidic treatment

Cited by 33 publications

References 43 publications

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

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

Mechanism of Charge Separation and Frontier Orbital Structure in Graphitic Carbon Nitride and Graphene Quantum Dots

Facile Production of a Fenton-Like Photocatalyst by Two-Step Calcination with a Broad pH Adaptability

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