g-C3N4 Composite Photocatalyst Research Articles

Photocatalytic persulfate activation by silica microsphere-supported g-C3N4 for efficient carbamazepine degradation

A silica-loaded g-C3N4 composite photocatalyst (M-SiO2/g-C3N4) was prepared by grinding amorphous SiO2 microspheres (M − SiO2) with melamine and calcining the resulting grinding products. This composite was used for photocatalytic persulfate (PMS) activation to degrade carbamazepine (CBZ). The results showed that the degradation efficiencies of CBZ by M-SiO2/g-C3N4-2.5 (39.16 % of g-C3N4)-activated PMS were 78.92 % and 100 % after simulated sunlight irradiation for 60 and 120 min, respectively. These values were significantly greater than those of the system with pure g-C3N4 (29.15 % and 42.4 %). In particular, the degradation efficiency of CBZ with M-SiO2/g-C3N4-2.5 decreased by only 9.47 % after 4 cycles of recycling. In the catalytic process, h+, SO4•− and O2•− were the main reactive species contributing to CBZ degradation. Compared with g-C3N4, loading g-C3N4 on the surface of M − SiO2 resulted in a decrease in g-C3N4 lamellar stacking, which increased the number of active surface sites and improved the separation and migration of photogenerated carriers, improving the degradation performance.

Z-scheme γ-Fe2O3/g-C3N4 in Photo-Fenton reaction for oxytetracycline degradation: Mechanism study and DFT calculation

With the urbanization and industrialization of the world, the pollution of water due to the misuse of antibiotics is increasing. In this study, a Z-scheme γ-Fe2O3/g-C3N4 composite photocatalyst was prepared, and the removal efficiency of oxytetracycline (OTC) reached 85.7% within 60 min under the Photo-Fenton reaction system higher than that of g-C3N4 and γ-Fe2O3. The composite has great anti-interference capability and sustainability, and the recyclability was demonstrated using hysteresis return lines data. The photoelectrochemical characterization was analyzed to investigate the effect of the building of Z-scheme heterojunction on the photogenerated carrier separation efficiency. The charge behavior of heterojunction interfaces was probed in conjunction with DFT calculations, and differential charge maps were used to visualize charge distributions to analyze possible charge transfer pathways. In addition, the active substances in the system were identified by ESR data and capture experiments. The results showed that ·OH was the dominant active substance for OTC degradation. Meanwhile, LC-MS data combined with Fukui function calculations led to the derivation of a possible degradation pathway dominated by ·OH. This research provides a reference for subsequent studies of non-homogeneous Photo-Fenton systems and offers a viable option for mitigating OTC pollution in water bodies.

ZIF-8/g-C3N4 photocatalysts: enhancing CO2 reduction through improved adsorption and photocatalytic performance.

Nowadays, the widespread concern over controlling CO2 emissions and mitigating the adverse effects of greenhouse gases on global climate has attracted significant attention. In this study, g-C3N4 was synthesized by thermopolymerizing urea. Subsequently, ZIF-8 was combined with g-C3N4 using an in situ deposition method, resulting in the fabrication of ZIF-8/g-C3N4 composite photocatalysts at various molar ratios. Effective incorporation of ZIF-8 into g-C3N4 suppressed the recombination of photogenerated electrons and holes, thereby enhancing CO2 capture capacity and preserving light absorption capabilities. The ZIF-8/g-C3N4 composite demonstrates excellent photocatalytic performance for CO2 reduction, where the optimized material exhibited a CO2 adsorption capacity 1.52 times that of pure g-C3N4 and increased the conversion of CO2 to CH4 by more than sevenfold. This study harnesses the superior CO2 adsorption properties of metal-organic frameworks to develop more efficient photocatalysts, enhancing CO2 conversion efficacy and offering insights for developing efficient photocatalysts that utilize CO2.

A pH-tolerant self-Fenton system with excellent antibiotics degradation performance over sulfonated g-C3N4 composite hematite photocatalyst

Photocatalytic self-Fenton technology can effectively purify antibiotic-contaminated water through an in-situ H2O2 synthesis and activation process. However, variations in acidity or alkalinity of wastewater can significantly impact the H2O2 synthesis and activation performance, making it necessary to expand the working pH range of the self-Fenton system. Herein, we construct a pH-tolerant self-Fenton photocatalyst (hematite/HSCN) by using grafted amino sulfonic to modulate the surface structure of g-C3N4 and loading of hematite to activate H2O2. Our findings reveal that sulfonated g-C3N4 (HSCN) exhibits enhanced proton capture capability, ensuring a stable proton supply during H2O2 synthesis under varying acidity or alkalinity conditions. Compared to g-C3N4, HSCN exhibits up to a 59.8-fold enhancement in H2O2 synthesis, maintaining high efficiency even under neutral and weak alkaline conditions. Furthermore, the loaded hematite nanoparticles effectively activate H2O2 in situ, enabling hematite/HSCN to degrade ibuprofen and tetracycline. Toxicity analysis shows a gradual reduction of pollutants toxicity during degradation, ultimately achieving mineralization and water purification. This study extends the working pH range of the photocatalytic self-Fenton system by enhancing the proton capture capability of the catalyst, providing a new insight for promoting the role of photocatalytic self-Fenton systems in environmental protection.

Treatment of antibiotics in water by SO3H-modified Ti3C2 Mxene photocatalytic collaboration with g-C3N4

Due to inherent limitations such as high carrier recombination efficiency, limited active sites, and suboptimal utilization of visible light, graphite-like carbon nitride (g-C3N4) has constrained its widespread application in water treatment within photocatalytic systems. In addressing this issue, the present study employed acid etching and sonochemistry to fabricate a Ti3C2-SO3H/g-C3N4 (TiCSOHCN) composite photocatalyst for the removal of tetracycline hydrochloride (TC). The amalgamation of Ti3C2-SO3H (TiCSOH) with g-C3N4 engendered the establishment of a discernible Schottky barrier, facilitating an expedited electron transfer rate. Photocatalytic degradation experiments demonstrate that, compared to individual components, the TiCSOHCN composite photocatalyst exhibits significantly enhanced photocatalytic activity. The removal efficiency of TC reaches 75.42 % within 2 h, and even after five cycles of experimentation, the degradation efficiency remains close to 70 %, indicating excellent stability. The augmentation can be predominantly ascribed to the cooperative influence arising from the synergy between Ti3C2-SO3H and g-C3N4. The augmentation of visible light responsiveness in g-C3N4, achieved through its modification with TiCSOH, resulted in the mitigation of photoelectron-hole pair recombination, consequently leading to an amelioration in the photocatalytic efficacy of the TiCSOHCN composite catalyst. Intermediate species arising from the degradation of tetracycline were discerned utilizing LC-MS, and conjectures regarding plausible degradation pathways were postulated. Evaluations of the ecotoxicological impact of tetracycline and its intermediates indicated a progressive diminution in toxicity throughout the course of the photocatalytic degradation process. Furthermore, through free radical capture and EPR tests, it was confirmed that ·O2– and ·OH are the primary active species responsible for the photocatalytic degradation of TC, substantiating the proposed rational photocatalytic degradation mechanism. This research provides an innovative approach to developing high-performance and stable photocatalysts.

Study on the performance of g-C3N4 composite TiO2 photocatalyst

In order to develop an efficient photocatalyst to solve the environmental pollution problem, in this work, g-C3N4 nanosheets were mixed with TiO2 by mechanical stirring method to successfully construct a binary composite photocatalyst C/T. After a series of test characterization analysis, the C/T composite photocatalyst degraded rhodamine B, and the degradation rate reached 99.4 % after 60 min of reaction. The binary composite formed a new nanoflower structure, which reduced the band gap value of the C/T composite photocatalyst to 2.20 V and promoted the separation efficiency of photogenerated electron-hole pairs and increased the number of active sites, so the photocatalytic performance of C/T was greatly enhanced. The capture measurement experiment was also carried out to determine that the degradation of pollutants by C/T mainly depended on two active substances, ·O2-and h+.

Synthesis and photocatalytic performance of composite g-C3N4 with functionalized multi-walled carbon nanotubes

A novel g-C3N4 composite photocatalyst was synthesized by one-step calcination using melamine and different functionalized multi-walled carbon nanotubes (MWCNT) as raw materials. The effect of additives on the photocatalytic performance of the composite g-C3N4 has been investigated. The results showed that the incorporation of functionalized MWCNT led to a porous structure in g-C3N4, increasing the specific surface area and availability of active sites. The addition of hydroxylated/carboxylated MWCNT (HMWCNT/CMWCNT) affected the band structure of g-C3N4 and reduced the band gap. The visible-light photocatalytic degradation efficiency of Rhodamine B (RhB) using g-C3N4 composited with various types and amounts of MWCNT was evaluated. Among them, g-C3N4 with 1 wt% CMWCNT showed the highest photocatalytic degradation efficiency of RhB and still had 92.71% photocatalytic activity after 5 cycles of degradation.

Highly Efficient Solar-Light-Active Ag-Decorated g-C3N4 Composite Photocatalysts for the Degradation of Methyl Orange Dye.

In this study, we utilized calcination and simple impregnation methods to successfully fabricate bare g-C3N4 (GCN) and x% Ag/g-C3N4 (x% AgGCN) composite photocatalysts with various weight percentages (x = 1, 3, 5, and 7 wt.%). The synthesized bare and composite photocatalysts were analyzed to illustrate their phase formation, functional group, morphology, and optical properties utilizing XRD, FT-IR, UV-Vis DRS, PL, FE-SEM, and the EDS. The photodegradation rate of MO under solar light irradiation was measured, and the 5% AgGCN composite photocatalyst showed higher photocatalytic activity (99%), which is very high compared to other bare and composite photocatalysts. The MO dye degradation rate constant with the 5% AgGCN photocatalyst exhibits 14.83 times better photocatalytic activity compared to the bare GCN catalyst. This photocatalyst showed good efficiency in the degradation of MO dye and demonstrated cycling stability even in the 5th successive photocatalytic reaction cycle. The higher photocatalytic activity of the 5% AgGCN composite catalyst for the degradation of MO dye is due to the interaction of Ag with GCN and the localized surface plasmon resonance (SPR) effect of Ag. The scavenger study results indicate that O2●- radicals play a major role in MO dye degradation. A possible charge-transfer mechanism is proposed to explain the solar-light-driven photocatalyst of GCN.

Immobilization of Bi-based metal-organic framework on g-C3N4 for efficient photocatalytic removal of tetracycline

The development of efficient photocatalysts for wastewater remediation has embarked increasing attention. In this work, Bi-based metal-organic framework (i.e., CAU-17) into was integrated into g-C3N4 matrix through a facile hydrothermal approach to fabricate CAU-17/g-C3N4composite photocatalysts. In particular, the composite exhibits a lily-like structure with a superior interface affinity between CAU-17 and g-C3N4. The introduction of CAU-17 results in a reduced charge transfer resistance and an enhanced photo-induced electron-hole separation rate. The hybrid CG-8 composite with a g-C3N4 loading of 8 wt% presented a Z-scheme heterostructure and the electron-hole pair recombination was effectively restricted. Photocatalytic removal of tetracycline was conducted and the kinetic constant of tetracycline degradation was improved 3.28 times in comparison of pristine CAU-17.

Ammonium phosphotungstate nanoparticle/ultrathin g-C3N4 composite photocatalysts with Z-scheme heterojunctions: preparation and application to organic contaminant degradation

Owing to their advantageous physical, chemical, electronic, and optical properties, two-dimensional (2D) materials are widely used as highly active visible-light photocatalysts. In this study, 3D/2D composite photocatalysts were prepared from ammonium phosphotungstate nanoparticles and 2D ultrathin graphitic carbon nitride by an impregnation method and were found to efficiently promote the photodegradation of rhodamine B and tetracycline in water under visible light irradiation. Photocatalytic degradation was maximum at a PW12NH4 loading of 20 wt% (UCN20), with photodegradation efficiencies of 93.40% and 69.6% for RhB and TC, respectively. The photocatalytic degradation rate using UCN20 was 5.8-fold higher for RhB and 2.2-fold higher for TC compared to those with UCN. This high performance is ascribed to the large specific surface areas and pore volumes of the composites and the reduced probability of photogenerated carrier recombination therein. The related degradation mechanism is believed to involve a Z-scheme charge transfer mode, which enhances the redox capability of composite photocatalysts and renders them suitable for the visible light-driven remediation of wastewater containing organic contaminants.

Synthesis and photocatalytic performance of g-C3N4/MeTMC-COP composite photocatalyst.

Covalent organic polymers have excellent application prospects in photocatalysis due to their excellent visible light absorption and structural designability. However, their fast recombination efficiency and complex preparation process limit their applications. Because of the above problems, this paper used urea to prepare g-C3N4 by high-temperature thermal polymerization and prepared g-C3N4 composite photocatalyst loaded with MeTMC-COP (g-C3N4/MeTMC-COP) by hydrothermal method. The photocatalytic hydrogen generation and photocatalytic degradation capabilities of composite photocatalysts with various mass ratios were investigated by characterizing the catalyst and using the organic dye Rhodamine B (RhB) as the pollutant. According to the research, the specific surface area of the g-C3N4/MeTMC-COP composite may reach 40.95m2g-1 when the mass ratio of g-C3N4 and MeTMC-COP is 3:1 (25.22m2g-1). It can offer more active sites for the photocatalytic process, and because the fluorescence peak intensity is the lowest, it has the lowest photogenerated electron-hole recombination efficiency. In comparison to g-C3N4, 3:1g-C3N4/MeTMC-COP can breakdown rhodamine B up to 100% after 75min of light irradiation; its photocatalytic hydrogen generation efficiency is 1.62 times that of g-C3N4, and the hydrogen evolution rate is 11.8μmolg-1h-1.

Scalable production of visible light photocatalysts with extended nanojunctions of WO3/g-C3N4 using zeta potential and phase control in sol-gel process

Semiconductor photocatalysis for water splitting is promising approach to the current energy and environmental crisis. Although heterostructure photocatalysts exhibit enhanced photoactivity, the construction of a continuous junction at the interfaces between heterogeneous substances. In this study, visible light responsive tungsten oxide/graphitic carbon nitride composite photocatalysts with extended nanojunctions (en-WO3/g-C3N4) were synthesized through a novel sol-gel process that controlled zeta potential and sol-gel phase. The rational design of porous sphere en-WO3/g-C3N4 composite photocatalyst was constructed micropores and intimate contact between WO3 nanoparticles (NPs) and 2-dimensional (2D) g-C3N4 platelet interface. The en-WO3/g-C3N4 composite photocatalyst exhibited improved UV–vis absorbance and reduced recombination rate of photogenerated electron-hole pairs. The photocatalytic activity of hydrogen production was significantly enhanced by facile mass transfer and efficient charge-carrier separation due to direct Z-scheme mechanism. As a result, the hydrogen (H2) production of optimal en-WO3/g-C3N4 photocatalyst was obtained as much as 1060 µmol h-1g-1 which is 3.8-folds higher than g-C3N4 photocatalyst (281 µmol h-1g-1). Also, the designed en-WO3/g-C3N4 showed good stability for H2 production for 12 h under visible light irradiation.

Facile Synthesis of Cr2O3 Embedded g-C3N4 Composites with Excellent Visible-Light Photocatalytic

Metal-free graphite carbon nitride (g-C3N4) has shown great potential in the environmental and energy fields. Herein, we illustrate the facile synthesis of Cr2O3-embedded g-C3N4 interlayer composites using an oil bath and thermal polymerization. The as-prepared 0.3-Cr2O3/g-C3N4 composite photocatalyst exhibited many excellent properties, including significantly promoting charge transfer and separation by establishing interlayer paths, having a large specific surface area, and significantly improving the light absorption intensity. Therefore, the composites of Cr2O3 embedded in g-C3N4 exhibit visible-light photocatalysis. After 50[Formula: see text]min of visible light illumination, the degradation rate reached 99%, which was approximately 9.5 times that of pure g-C3N4. Repeatability test results show that the prepared 0.3-Cr2O3/g-C3N4 catalyst has prominent stability and repeatability. Then, we explain the mechanism of RhB degradation using the synthesized photocatalyst. This work provides a reference for the comprehensive development of g-C3N4 and offers broad prospects for photocatalytic applications of other layered materials.

Nitrogen-doping coupled with cerium oxide loading co-modified graphitic carbon nitride for highly enhanced photocatalytic degradation of tetracycline under visible light

The increasingly serious pollution of antibiotics brings an enormous threat to the ecological environment and human health. Graphite phase carbon nitride (g-C3N4), as a popular photocatalytic material, is widely used in photocatalytic degradation of antibiotics in water. In order to make up for the shortage of g-C3N4 monomer, CeO2/N-doped g-C3N4 (CeNCN) composite photocatalysts co-modified with nitrogen doping and CeO2 loading were designed and synthesized with the idea of expanding visible light absorption and promoting photogenerated carrier separation. CeNCN exhibits excellent photodegradation performance, the removal rate of tetracycline reached 80.09% within 60 min, which is much higher than that of g-C3N4 (CN) and N-doped g-C3N4 (NCN); and the quasi-first-order degradation rate constant is 0.0291, which is 7.86 and 2.29 times higher than CN and NCN. Electron spin resonance and free radical trapping experiments confirmed that h+, O2− and OH are the active substances in the photocatalytic system. After 5 cycles, the degradation efficiency of tetracycline still exceeds 75%, which indicates that CeNCN has good stability. This work proves that N-doping and CeO2 loading can effectively broaden the photoresponse range of g-C3N4, facilitate the separation of photogenerated electron-hole pairs, and provide a reference for the construction of g–C3N4–based photocatalyst with high-efficiency photodegradation activity.

Hydrothermal synthesis of spherical g-C3N4 and CdS composite photocatalyst with enhanced visible light photocatalytic activity

In this paper, spherical g-C3N4 modified by N defect and O doping was prepared by a simple hydrothermal method, and combined with CdS to form a direct Z-type heterojunction. Combined with a series of characterizations (XRD, SEM, BET, FTIR and UV–vis DRS), the results show that the addition of CTAB brings a lot of positive charges on the surface of N-OCN. According to the principle of electrostatic attraction, positively charged N-OCN negatively charged CdS attract each other, which strengthens the close contact between CdS and N-OCN and plays an important role in stabilizing the formation of heterojunction. CdS is anchored to N-OCN through electrostatic interaction. Under the irradiation of visible light, the electrons on CB on positively charged N-OCN combine with holes on negatively charged CdS valence band, which improves the redox ability in photocatalytic reaction system. Taking methyl orange (MO) as a pollutant degradation model, the possible degradation mechanism was discussed in detail. This study provides a simple, effective and wide application method for the modification of g-C3N4.

Microtubular carbonized cotton fiber modified g-C3N4 for the enhancement of visible-light-driven photocatalytic activity

The combination of graphitic carbon nitride (g-C3N4) and carbonized material is a promising strategy to improve g-C3N4’s visible light absorption and charge separation efficiency. Herein, a carbonized cotton fiber (CCF) modified pure g-C3N4 (PCN/CCF) composite photocatalyst is prepared by a one-step calcination method for visible-light-driven photocatalytic. Due to CCF excellent electronic transmission and strong absorption of visible light, the green-cheap carbonized cotton fiber in the composite photocatalyst (PCN/CCF) can effectively enhance charge separation efficiency and enhances the visible light absorption of PCN. And the degradation efficiency of PCN/CCF-6 to methyl orange can reach 90% in 1 h under visible light irradiation. The photodegradation constant of PCN/CCF-6 is 0.03105 min−1, which is 8 times that of bulk carbon nitride (BCN) and twice that of the pure g-C3N4 (PCN). This catalyst also shows excellent degradation performance against other pollutants (Rh B, TC). PCN/CCF provide an effective way for carbon-based materials to assist high-efficiency photocatalytic degradation of organic pollutants.

Preparation of heterogeneous TiO2/g-C3N4 with a layered mosaic stack structure by use of montmorillonite as a hard template approach: TC degradation, kinetic, mechanism, pathway and DFT investigation

Photocatalysis is considered one of the most promising methods for removing antibiotics from wastewater. In this work, natural mineral montmorillonite was used as a hard template to prepare g-C3N4 and TiO2 composite photocatalysts with a layered mosaic stack structure through a double intercalation process for the first time. Benefiting from the layered mosaic stack structure, enhanced visible-light response, and effective charge transfer induced by uniform and compact heterojunctions, the prepared photocatalyst showed excellent photodegradation efficiency to remove tetracycline (TC) pollutants. The degradation rate of TC was 97.0% within 60 min. The photocatalytic degradation rate constant of the optimized composite was 0.058 min−1, which was approximately 6.21 higher than that of g-C3N4 (0.009 min−1). Density functional theory (DFT) calculations predicted that the degradation of TC mainly occurred at the boundaries rather than in the interlayer spaces. The layered mosaic stack structure of g-C3N4 and TiO2 prepared with montmorillonite suggests its potential to serve as an efficient photocatalyst for TC in wastewater treatment, and the method could provide some inspiration for the design and construction of efficient photocatalysts.

Construction of novel in-situ photo-Fenton system based on modified g-C3N4 composite photocatalyst

In this study, a reduced g-C3N4/PDI/Fe (R-gCPF) photocatalyst was synthesized by loading Fe ion onto a reduced g-C3N4/PDI (R-gCP), which was obtained by reducing g-C3N4/PDI with NaBH4. The synthesized R-gCPF photocatalyst was used to construct a novel in-situ photo-Fenton system under visible light for pollutants removal. The R-gCPF2 (0.7% mass ratio of Fe/R-gCP) exhibited the optimal degradation efficiency toward benzoic acid (BA) and the photocatalytic degradation was much better than that of the unmodified g-C3N4/PDI (gCP). The X-ray photoelectron spectroscopy (XPS) characterization indicated that Fe was successfully loaded and bounded to the R-gCP material in the form of Fe2O3. The quenching experiments and the electron paramagnetic resonance (EPR) spectroscopic analysis revealed that the photo-Fenton system was built up, and water was oxidized to OH in the system. Further, the Mott-Schottky and UV–vis diffuse reflectance spectrometry (UV–vis DRS) measurements confirmed the ability of valence band on R-gCPF to oxidize water. Photoluminescence spectral (PL) analysis indicated that loaded Fe could promote the separation of photogenerated electrons and holes, and consequently improved the photocatalytic efficiency of materials. The effect of initial pH, different ions and dissolved organic matter (DOM) on BA degradation was also studied. The stability of the photocatalyst was confirmed by recycle and the leaching experiments.

Recent advances in g-C3N4 composites within four types of heterojunctions for photocatalytic CO2 reduction.

Studies of photocatalytic conversion of CO2 into hydrocarbon fuels, as a promising solution to alleviate global warming and energy issues, are booming in recent years. Researchers have focused their interest in developing g-C3N4 composite photocatalysts with intriguing features of robust light harvesting ability, excellent catalysis, and stable performance. Four types of heterojunctions (type-II, Z-scheme, S-scheme and Schottky) of the g-C3N4 composites are widely adopted. This review aims at presenting and comparing the photocatalytic mechanisms, characteristics, and performances of g-C3N4 composites concerning these four types of heterojunctions. Besides, perspectives and undergoing efforts for further development of g-C3N4 composite photocatalysts are discussed. This review would be helpful for researchers to gain a comprehensive understanding of the progress and future development trends of g-C3N4 composite heterojunctions for photocatalytic CO2 reduction.

2D-2D ZnO/N doped g-C3N4 composite photocatalyst for antibiotics degradation under visible light.

ZnO and g-C3N4 provide excellent photocatalytic properties for degradation of antibiotics in pharmaceutical wastewater. In this work, 2D–2D ZnO/N doped g-C3N4 (NCN) composite photocatalysts were prepared for degradation of tetracycline (TC), ciprofloxacin (CIP) and ofloxacin (OFLX). The addition of ZnO resulted in higher separation efficiency and lower recombination rate of photogenerated charge under visible light. The composite photocatalyst showed better degradation performance compared to ZnO or NCN alone. The TC degradation reached 81.3% in 15 minutes by applying the prepared 20% ZnO/NCN composite photocatalyst, showing great competitiveness among literature reported g-C3N4 based photocatalysts. After 30 minutes, the degradation rate of TC, CIP and OFLX reached 82.4%, 64.4% and 78.2%, respectively. The TC degradation constant of the composite photocatalyst was 2.7 times and 6.4 times higher than NCN and CN, respectively. Radical trapping experiments indicated that ·O2− was the dominant active substance. The transference of excited electrons from the conduction band (CB) of NCN to ZnO enhanced the separation of photogenerated electron–hole pairs and simultaneously suppressed their recombination. This study provides a possibility for the design of high-performance photocatalysts for antibiotics degradation in wastewater.