Oxygen functional groups in graphitic carbon nitride for enhanced photocatalysis

Hybrid graphenic and iron oxide photocatalysts for the decomposition of synthetic chemicals

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals that resist degradation, posing a significant environmental and health risk. Current methods for removing PFAS from water are often complex and costly. Here we report a simple, cost-effective method to synthesize an iron oxide/graphenic carbon (Fe/g-C) hybrid photocatalyst for PFAS degradation. This photocatalyst efficiently degrades perfluorooctanoic acid (PFOA), a common type of PFAS, achieving over 85% removal within 3 hours under ultraviolet light. The catalyst also maintains high degradation rates over extended periods, demonstrating its stability and potential for long-term use. This innovative approach offers a promising solution for addressing PFAS contamination in water, contributing to a cleaner and healthier environment.

Oxygen-enriched carbon quantum dots from coffee waste: Extremely active organic photocatalyst for sustainable solar-to-H2O2 conversion

Solar-driven artificial photosynthesis offers a promising avenue for hydrogen peroxide (H2O2) generation, an efficient and economical replacement for current methods. The efficiency and selectivity hurdles of the two-electron oxygen reduction reaction (ORR) in solar-to- H2O2 conversion are substantial barriers to large scale production. In this manuscript, a simple biomass-assisted synthesis was performed to produce oxygen-enriched carbon quantum dots (OE-CQDs) from spent coffee waste, acting as an efficient photocatalyst for solar-powered H2O2 production. OE-CQDs can stabilize and store light-generated electrons effectively, boosting charge separation and enhancing photocatalytic performance with longevity. The maximal photocatalytic H2O2 production was achieved viz the utilization of OE-CQDs with generation rate of 356.86 μmol g-1 h-1 by retaining 80% activity without any external sacrificial donors. The outstanding performance of synthesized OE-CQDs under light exposure at wavelength (λ) of 280 nm has been ensured by the quantum yield value of 9.4% upon H2O2 generation. The combinatorial benefits of OE-CQDs with their authentic crystalline structure and oxygen enrichment, is expected to be enhancing the ORR activity through accelerating charge transfer, and optimizing oxygen diffusion. Consequently, our eco-friendly method holds considerable promise for creating highly efficient, metal-free photocatalysts for artificial H2O2 production.

Sugars induced exfoliation of porous graphitic carbon nitride for efficient hydrogen evolution in photocatalytic water-splitting reaction

Photocatalytic hydrogen evolution holds great promise for addressing critical energy and environmental challenges, making it an important area in scientific research. One of the most popular photocatalysts is graphitic carbon nitride (gCN), which has emerged as a noteworthy candidate for hydrogen generation through water splitting. However, ongoing research aims to enhance its properties for practical applications. Herein, we introduce a green approach for the fabrication of porous few-layered gCN with surface modifications (such as oxygen doping, carbon deposition, nitrogen defects) with promoted performance in the hydrogen evolution reaction. The fabrication process involves a one-step solvothermal treatment of bulk graphitic carbon nitride (bulk-gCN) in the presence of different sugars (glucose, sucrose, and fructose). Interestingly, the conducted time-dependent process revealed that porous gCN exfoliated in the presence of fructose at 180 °C for 6 h (fructose_6h) exhibits a remarkable 13-fold promotion of photocatalytic hydrogen evolution compared to bulk-gCN. The studied materials were extensively characterized by microscopic and spectroscopic techniques, allowing us to propose a reaction mechanism for hydrogen evolution during water-splitting over fructose_6h. Furthermore, the study highlights the potential of employing a facile and environmentally friendly fructose-assisted solvothermal process to improve the efficiency and stability of catalysts based on graphitic carbon nitride.

A Breakthrough in Photocatalytic Wastewater Treatment: The Incredible Potential of g-C3N4/Titanate Perovskite-Based Nanocomposites

Water pollution has emerged as a major global environmental crisis due to the massive contamination of water resources by the textile dyeing industry, organic waste, and agricultural residue. Since water is fundamental to life, this grave disregard puts lives at risk, making the protection of water resources a serious issue today. Recent research has shown great interest in improving the photocatalytic performance of graphitic carbon nitride (g-C3N4) for wastewater treatment. However, the photocatalytic removal activity of pure g-C3N4 is poor, owing to its minimal surface area, fast recombination of photo-generated electron-hole pairs, and poor light absorption. Recently, titanate perovskites (TNPs) have attracted significant attention in both environmental remediation and energy conversion due to their exceptional structural, optical, physiochemical, electrical, and thermal properties. Accordingly, TNPs can initiate a variety of surface catalytic reactions and are regarded as an emerging category of photocatalysts for sustainability and energy-related industries when exposed to illumination. Therefore, in this review article, we critically discuss the recent developments of extensively developed g-C3N4/TNPs that demonstrate photocatalytic applications for wastewater treatment. The different synthetic approaches and the chemical composition of g-C3N4/TNP composites are presented. Additionally, this review highlights the global research trends related to these materials. Furthermore, this review provides insight into the various photocatalytic mechanisms, including their potential impact and significance. Also, the challenges faced by such materials and their future scope are discussed.

Computational Investigation of Interactions between Carbon Nitride Dots and Doxorubicin

The study of carbon dots is one of the frontiers of materials science due to their great structural and chemical complexity. These issues have slowed down the production of solid models that are able to describe the chemical and physical features of carbon dots. Recently, several studies have started to resolve this challenge by producing the first structural-based interpretation of several kinds of carbon dots, such as graphene and polymeric ones. Furthermore, carbon nitride dot models established their structures as being formed by heptazine and oxidized graphene layers. These advancements allowed us to study their interaction with key bioactive molecules, producing the first computational studies on this matter. In this work, we modelled the structures of carbon nitride dots and their interaction with an anticancer molecule (Doxorubicin) using semi-empirical methods, evaluating both geometrical and energetic parameters.

Construction of Pt@BiFeO3 Xerogel-Supported O-g-C3N4 Heterojunction System for Enhanced Visible-Light Activity towards Photocatalytic Degradation of Rhodamine B

Synthetic organic pigments from the direct discharge of textile effluents are considered as colossal global concern and attract the attention of scholars. The efficient construction of heterojunction systems involving precious metal co-catalysis is an effective strategy for obtaining highly efficient photocatalytic materials. Herein, we report the construction of a Pt-doped BiFeO₃/O-g-C₃N₄ (Pt@BFO/O-CN) S-scheme heterojunction system for photocatalytic degradation of aqueous rhodamine B (RhB) under visible-light irradiation. The photocatalytic performances of Pt@BFO/O-CN and BFO/O-CN composites and pristine BiFeO₃ and O-g-C₃N₄ were compared, and the photocatalytic process of the Pt@BFO/O-CN system was optimized. The results exhibit that the S-scheme Pt@BFO/O-CN heterojunction has superior photocatalytic performance compared to its fellow catalysts, which is due to the asymmetric nature of the as-constructed heterojunction. The as-constructed Pt@BFO/O-CN heterojunction reveals high performance in photocatalytic degradation of RhB with a degradation efficiency of 100% achieved after 50 min of visible-light irradiation. The photodegradation fitted well with pseudo-first-order kinetics proceeding with a rate constant of 4.63 × 10^-2 min^-1. The radical trapping test reveals that h⁺ and ^•O₂^- take the leading role in the reaction, while the stability test reveals a 98% efficiency after the fourth cycle. As established from various interpretations, the considerably enhanced photocatalytic performance of the heterojunction system can be attributed to the promoted charge carrier separation and transfer of photoexcited carriers, as well as the strong photo-redox ability established. Hence, the S-scheme Pt@BFO/O-CN heterojunction is a good candidate in the treatment of industrial wastewater for the mineralization of organic micropollutants, which pose a grievous threat to the environment.

Facile synthesis of cadmium-doped graphite carbon nitride for photocatalytic degradation of tetracycline under visible light irradiation

In recent years, using semiconductor photocatalysts for antibiotic contaminant degradation under visible light has become a hot topic. Herein, a novel and ingenious cadmium-doped graphite phase carbon nitride (Cd-g-C₃N₄) photocatalyst was successfully constructed via the thermal polymerization method. Experimental and characterization results revealed that cadmium (Cd) was well doped at the g-C₃N₄ surface and exhibited high intercontact with g-C₃N₄. Additionally, the introduction of cadmium significantly improved the photocatalytic activity, and the optimum degradation efficiency of tetracycline (TC) reached 98.1%, which was exceeded 2.0 times that of g-C₃N₄ (43.9%). Meanwhile, the Cd-doped sample presented a higher efficiency of electrical conductivity, light absorption property, and photogenerated electron-hole pair migration compared with g-C₃N₄. Additionally, the quenching experiments and electron spin-resonance tests exhibited that holes (h⁺), hydroxyl radicals (•OH), superoxide radicals (•O₂^-) were the main active species involved in TC degradation. The effects of various conditions on photocatalytic degradation, such as pH, initial TC concentrations, and catalyst dosage, were also researched. Finally, the degradation mechanism was elaborated in detail. This work gives a reasonable point to synthesizing high-efficiency and economic metal-doped photocatalysts.

Enhanced adsorption and visible-light photocatalysis on TiO2 with in situ formed carbon quantum dots

Carbon quantum dots (CQDs) can be used to modify TiO₂ to extend the light absorption threshold and enhance its photocatalytic efficiency. In this study, different amounts of CQDs modified TiO₂ (CQDs-x/TiO₂) were synthesized by a facile, mild, and environmental friendly hydrothermal method at a low temperature. The physicochemical properties were investigated by a variety of advanced characterization techniques. It was found that the anchoring of CQDs endowed the CQDs-x/TiO₂ with a large specific surface area, which is beneficial to adsorb more organic pollutants and promote the rate of photocatalytic oxidation. The XRD results also showed that the in situ formation of CQDs on the surface of TiO₂ made the crystallinity of TiO₂ tend to be complete. Among these photocatalysts, CQDs-20/TiO₂ showed the highest pollutant removal efficiency under visible light irradiations. The classical quenching tests revealed that the O₂^•-, ^•OH, and hole (h⁺) were the oxidizing species. Among them, h⁺ was the primary factor contributing to the degradation. The electrochemical tests showed that the anchoring of CQDs on TiO₂ increased the photocurrent by about four times, as compared with the pure TiO₂. In particular, the cyclic voltammetry results showed that the photo-generated electrons of CQDs were freer to transfer to TiO₂ under visible light irradiations, promoting the separation of photo-generated electrons and holes. This study explains adequately why the CQDs/TiO₂ system has a good photocatalytic degradation of organic compounds.

Carbon nitride-based Z-scheme heterojunctions for solar-driven advanced oxidation processes

Solar-driven advanced oxidation processes (AOPs) via direct photodegradation or indirect photocatalytic activation of typical oxidants, such as hydrogen peroxide (H₂O₂), peroxymonosulfate (PMS), and peroxydisulfate (PDS), have been deemed to be an efficient technology for wastewater remediation. Artificial Z-scheme structured materials represent a promising class of photocatalysts due to their spatially separated charge carriers and strong redox abilities. Herein, we summarize the development of metal-free graphitic carbon nitride (g-C₃N₄, CN)-based direct and indirect Z-scheme photocatalysts for solar-driven AOPs in removing organic pollutants from water. In the work, the classification of AOPs, definition and validation of Z-schemes are summarized firstly. The innovative engineering strategies (e.g., morphology and dimensionality control, element doping, defect engineering, cocatalyst loading, and tandem Z-scheme construction) over CN-based direct Z-scheme structure are then examined. Rational design of indirect CN-based Z-scheme systems using different charge mediators, such as solid conductive materials and soluble ion pairs, is further discussed. Through examining the relationship between the Z-scheme structure and activity (charge transfer and separation, light absorption, and reaction kinetics), we aim to provide more insights into the construction strategies and structure modification on CN-based Z-schemes towards improving their catalytic performances in AOPs. Lastly, limitations, challenges, and perspectives on future development in this emerging field are proposed.

Dye Removal Ability of Pure and Doped Graphitic Carbon Nitride

Background:

Rapid escalation in textile, paper, pesticides, pharmaceuticals and several other chemical based manufacturing industries due to amplification in human requirements have proportionately contributed to the extreme contamination of water ecosystem, resulted from the discharge of toxic pollutants from industries. Effluents from textile industries are comprised of coloured dyes like Rhodamine B, Methyl Orange, Methylene Blue and phenolic compounds which deserve special mention owing to their non-biodegradable, carcinogenic and severe detrimental nature. Urgent needs to ameliorate this fast declining environmental situation are of immense necessity in current scenario.

Objectives:

Objectives: In this regard, graphitic carbon nitride (GCN) is a distinguished material for water purification-based applications because of its exclusive characteristics making it highly prospective for degradation of toxic dyes from water by catalysis and adsorption techniques. GCN has been a material of conspicuous interest in recent times owing to its two dimensional sheets like structure with favourable surface area, and cost-effective synthesis approaches along with high production yield. This article presents a detail study of different aspects of GCN as a material of potential for water purification. Through extensive literature survey it has been shown that GCN is an effective material to be used in the fields of application. Several effective procedures like catalysis or adsorption for removal of dyes from water have been discussed with their basic science behind.

Conclusions:

This systematic effort shows that GCN can be considered to be one of the most efficient water purifier with further advantages arising from its easy and cost effective large scale synthesis.

Point-Defect Engineering: Leveraging Imperfections in Graphitic Carbon Nitride (g-C3 N4 ) Photocatalysts toward Artificial Photosynthesis

Graphitic carbon nitride (g-C₃ N₄ ) is a kind of ideal metal-free photocatalysts for artificial photosynthesis. At present, pristine g-C₃ N₄ suffers from small specific surface area, poor light absorption at longer wavelengths, low charge migration rate, and a high recombination rate of photogenerated electron-hole pairs, which significantly limit its performance. Among a myriad of modification strategies, point-defect engineering, namely tunable vacancies and dopant introduction, is capable of harnessing the superb structural, textural, optical, and electronic properties of g-C₃ N₄ to acquire an ameliorated photocatalytic activity. In view of the burgeoning development in this pacey field, a timely review on the state-of-the-art advancement of point-defect engineering of g-C₃ N₄ is of vital significance to advance the solar energy conversion. Particularly, insights into the intriguing roles of point defects, the synthesis, characterizations, and the systematic control of point defects, as well as the versatile application of defective g-C₃ N₄ -based nanomaterials toward photocatalytic water splitting, carbon dioxide reduction and nitrogen fixation will be presented in detail. Lastly, this review will conclude with a balanced perspective on the technical and scientific hindrances and future prospects. Overall, it is envisioned that this review will open a new frontier to uncover novel functionalities of defective g-C₃ N₄ -based nanostructures in energy catalysis.

Carbon-based metal-free electrocatalysts: from oxygen reduction to multifunctional electrocatalysis

Since the discovery of N-doped carbon nanotubes as the first carbon-based metal-free electrocatalyst (C-MFEC) for oxygen reduction reaction (ORR) in 2009, C-MFECs have shown multifunctional electrocatalytic activities for many reactions beyond ORR, such as oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO₂RR), nitrogen reduction reaction (NRR), and hydrogen peroxide production reaction (H₂O₂PR). Consequently, C-MFECs have attracted a great deal of interest for various applications, including metal-air batteries, water splitting devices, regenerative fuel cells, solar cells, fuel and chemical production, water purification, to mention a few. By altering the electronic configuration and/or modulating their spin angular momentum, both heteroatom(s) doping and structural defects (e.g., atomic vacancy, edge) have been demonstrated to create catalytic active sites in the skeleton of graphitic carbon materials. Although certain C-MFECs have been made to be comparable to or even better than their counterparts based on noble metals, transition metals and/or their hybrids, further research and development are necessary in order to translate C-MFECs for practical applications. In this article, we present a timely and comprehensive, but critical, review on recent advancements in the field of C-MFECs within the past five years or so by discussing various types of electrocatalytic reactions catalyzed by C-MFECs. An emphasis is given to potential applications of C-MFECs for energy conversion and storage. The structure-property relationship for and mechanistic understanding of C-MFECs will also be discussed, along with the current challenges and future perspectives.

Efficient solar light facilitated photo-oxidative detoxification of gaseous 2-chloroethyl ethyl sulfide on ZrO2-doped g-C3N4 under dry and humid air

Photo-oxidation of chemical warfare agents is considered a promising strategy to cope with threats from accidental or intentional release. In this study, heterostructure photocatalysts comprising different amounts of zirconium oxide (ZrO₂) over carbon nitride (CN) were synthesized via simple thermal exfoliation, followed by a precipitation method. The successful photocatalytic detoxification activity of the as-prepared photocatalyst was analyzed against 2-chloroethyl ethyl sulfide (CEES) under simulated solar light and natural sunlight irradiation in dry and humid air. As the CN/ZrO₂ demonstrated a high surface area and oxygen doping, the addition of small amounts of the ZrO₂ phase could lead to enhanced photoreactivity in surface chemistry. The as-prepared (CN/ZrO₂-II) degraded 95% of CEES under simulated solar light and 70% under natural sunlight within 90 min. The photo-detoxification of CEES was associated with the generation of holes (h⁺) and activation of oxygen to superoxide radicals (•O₂). Based on analysis results, a reaction mechanism was suggested. The activity of the used photocatalyst could be recovered to 90% of the fresh photocatalyst activity via simple water washing. However, as sulfurous compounds were accumulated on the surface in subsequent cyclic tests, solvent washing was also suggested to maintain high detoxification performance.

Carbon nitride-based photocatalysts for the mitigation of water pollution engendered by pharmaceutical compounds

In recent decades, the destructive impact of active pharmaceutical ingredients (API) present in surface and drinking water on aquatic and terrestrial life forms becomes a major concern of researchers. API like diclofenac (DCF), carbamazepine (CBZ), tetracycline (TC), and sulfamethoxazole (SME) found in water bodies cause antimicrobial resistance and are potent carcinogens and endocrine disruptors. Conventional wastewater treatment methods possess some drawbacks and were found to be insufficient for the effective removal of APIs. Visible light-assisted semiconductor photocatalysis has become an alternative choice for tackling this worse scenario. Graphitic carbon nitride, a metal-free visible light active semiconductor photocatalyst is an emerging hotspot nanomaterial whose practical utility in water purification is widely recognized. This review comes up with an insightful outlook on the panorama of recent progress in the field of g-C₃N₄-assisted photocatalytic systems for the eradication of APIs. In addition, the review summarizes various strategies adopted for the broad-spectrum utilization of visible light and the enhancement of charge separation of pristine g-C₃N₄. The mechanistic pathways followed by different pharmaceuticals during their photocatalytic degradation process were also briefly discussed.

Electrostatic interaction mechanism of visible light absorption broadening in ion-doped graphitic carbon nitride

H₂O₂ treated K-doped graphitic carbon nitride presents an enhanced visible light absorption, which is due to the electrostatic attraction between K ions and OOH ions inside graphitic carbon nitride.

Modification of Graphitic Carbon Nitride with Hydrogen Peroxide

Graphitic carbon nitride (GCN) was synthetized by heating melamine and then it was thermally exfoliated for 1-3 h in air. Both bulk and exfoliated GCN nanomaterials were treated in the 10-30% aqueous solutions of H₂O₂ for us to study their modification. The light absorption properties were observed by the reddish color and the red-shifts of their UV-Vis spectra. The content of oxygen increased and hydrogen peroxide was supposed to partially oxidize C-OH groups to C=O ones and to form C-O-C groups instead of edge C-NH-C ones. The GCN structure changes were not observed. However, a surface modification of the GCN materials was recognized by their changed photocatalytic activities tested by means of Acid Orange 7 (AO7) and Rhodamines B (RhB), zeta-potentials, and neutralization titration curves.

Photocatalytic activation of peroxymonosulfate by surface-tailored carbon quantum dots

In this study, carbon quantum dots (CQDs) were synthesized by a low-cost and scalable approach and the oxygen functional groups were fine-tuned by chemical post-treatment. It was found that the CQDs could be applied as visible-light-responsive photocatalysts for activation of peroxymonosulfate (PMS) and remediation of aqueous organic dyes. Phenylhydrazine modified CQDs (CQDs-PH) presented high efficiency for degradation of methylene blue due to selective removal of carboxylic groups and inhibited recombination of photogenerated electron-hole pairs. The effects of catalyst dosage, species and concentrations of dyes, and initial pH values on the photodegradation efficiency were systematically investigated and the alkaline condition facilitates the separation of photoinduced charge carriers and promotes the dye decoloration. The reactive oxygen species produced in the photocatalysis were identified by radical quenching tests and the mechanism was elucidated. Superoxide radicals were generated from PMS activation via electron transfer from CQDs and played the primary role in organic oxidation. In addition, photogenerated holes on the valence band of CQDs also participated in the dye decomposition.

Photochemical transformation of C3N4 under UV irradiation: Implications for environmental fate and photocatalytic activity

In this study, the photo-transformations of bulk C₃N₄ (CN) and oxidized C₃N₄ (OCN) under UV-irradiation were examined. Through NO₃^- release measurements, we found that the photo-transformation rate of OCN is higher than that of CN. Various characterization results revealed the structural and chemical properties changes of CN and OCN after photo-transformation. We proposed that under reactive oxygen species attack, CN and OCN were gradually broken into smaller fragments and finally mineralized into NO₃-, CO₂, and H₂O through the circular reactions of deamination-hydroxylation-decarboxylation. Through the zeta potential measurements and sedimentation experiments, the influence of photo-transformation on the water stabilities of CN and OCN were assessed. The stability of CN in water increased while the water stability of OCN decreased after photo-transformation, implying that the changes to C₃N₄-based materials caused by photo-transformation may significantly impact their environmental behaviors. Moreover, the photocatalytic activities of the photo-transformed OCN and CN substantially decreased, indicating that the structural changes might be the main reason for their photocatalytic activity loss. These findings highlight the non-negligible influence of photo-transformation on the fate of C₃N₄ in aquatic environments, as well as on the photochemical stability during its use.

Porous graphitic carbon nitride for solar photocatalytic applications

Photocatalysis is attracting increased attention in solving the energy crisis and environmental pollution. Graphitic carbon nitride (g-C3N4), a non-metal photocatalyst, has been regarded as an ideal photocatalyst to solve these problems because of its chemical stability and unique optical properties. However, traditional g-C3N4 exhibits moderate photocatalytic activity due to its low specific surface area and fast recombination rate of photogenerated electrons. Among the many modified g-C3N4 materials, porous carbon nitride (PCN) can solve the shortcomings of traditional g-C3N4 because of PCN's increased number of surface-active sites, specific surface area, light harvesting, diffusion and adsorption/activation. However, a frontier, comprehensive summary of the development of PCN is less reported. Thus, a review on recent developments in PCN research is urgently needed to further promote its advancement. In this review, the synthesis methods, structures and properties and photocatalytic applications of PCN photocatalysts are described in detail. The current challenges and future development of PCN/PCN-based photocatalysts are discussed. This review may present an up-to-date view of the PCN development to provide an in-depth understanding of PCN-based photocatalysts.

Dual-defect-modified graphitic carbon nitride with boosted photocatalytic activity under visible light

The development of photocatalysts that efficiently degrade organic pollutants is an important environmental-remediation objective. To that end, we report a strategy for the ready fabrication of oxygen-doped graphitic carbon nitride (CN) with engendered nitrogen deficiencies. The addition of KOH and oxalic acid during the thermal condensation of urea led to a material that exhibits a significantly higher pseudo-first-order rate constant for the degradation of bisphenol A (BPA) (0.0225 min-1) compared to that of CN (0.00222 min-1). The enhanced photocatalytic activity for the degradation of BPA exhibited by the dual-defect-modified CN (Bt-OA-CN) is ascribable to a considerable red-shift in its light absorption compared to that of CN, as well as its modulated energy band structure and more-efficient charge separation. Furthermore, we confirmed that the in-situ-formed cyano groups in the Bt-OA-CN photocatalyst act as strong electron-withdrawing groups that efficiently separate and transfer photo-generated charge carriers to the surface of the photocatalyst. This study provides novel insight into the in-situ dual-defect strategy for g-C3N4, which is extendable to the modification of other photocatalysts; it also introduces Bt-OA-CN as a potential highly efficient visible-light-responsive photocatalyst for use in environmental-remediation applications.

Facile synthesis of g-C3N4(0.94)/CeO2(0.05)/Fe3O4(0.01) nanosheets for DFT supported visible photocatalysis of 2-Chlorophenol

Visible light active g-C3N4(0.94)/CeO2(0.05)/Fe3O4(0.01) ternary composite nanosheets were fabricated by facile co-precipitation routes. The density functional theory (DFT) computations investigated changes in geometry and electronic character of g-C3N4 with CeO2 and Fe3O4 addition. Chemical and surface characterizations were explored with XRD, XPS, SEM, TEM, PL, DRS and Raman measurements. DRS and PL spectroscopy evidenced the energy band gap tailoring from 2.68 eV for bulk g-C3N4 and 2.92 eV for CeO2 to 2.45 eV for the ternary nanocomposite. Efficient electron/hole pair separation, increase in red-ox species and high exploitation of solar spectrum due to band gap tailoring lead to higher degradation efficiency of g-C3N4(0.94)/CeO2(0.05)/Fe3O4(0.01). Superior sun light photocatalytic breakdown of 2-Chlorophenol was observed with g-C3N4 having CeO2 loading up to 5 wt%. In case of ternary nanocomposites deposition of 1 wt% Fe3O4 over g-C3N4/CeO2 binary composite not only showed increment in visible light catalysis as predicted by the DFT studies, but also facilitated magnetic recovery. The g-C3N4(0.94)/CeO2(0.05)/Fe3O4(0.01) nanosheets showed complete mineralization of 25 mg.L-1 2-CP(aq) within 180 min exposure to visible portion of sun light and retained its high activity for 3 consecutive reuse cycles. The free radical scavenging showed superoxide ions and holes played a significant role compared to hydroxyl free radicals while chromatographic studies helped establish the 2-CP degradation mechanism. The kinetics investigations revealed 2.55 and 4.04 times increased rate of reactions compared to pristine Fe3O4 and CeO2, showing highest rate constant value of 18.2 × 10-3 min-1 for the ternary nanocomposite. We present very persuasive results that can be beneficial for exploration of further potential of g-C3N4(0.94)/CeO2(0.05)/Fe3O4(0.01) in advance wastewater treatment systems.

Fabrication of interlayer β-CD/g-C3N4@MoS2 for highly enhanced photodegradation of glyphosate under simulated sunlight irradiation

Graphitic carbon nitride (g-C3N4) has been considered to be a promising metal-free photocatalyst, although the high recombination rate of charge carriers and poor absorption of visible light have limited its applications. In order to overcome these problems, an interlayer composite photocatalyst that comprised β-cyclodextrin (β-CD), oxygen-doped C3N4 (O-C3N4) and molybdenum disulfide (MoS2) was successfully constructed for the highly enhanced photodegradation of glyphosate in this study. The structure and morphology, optical properties, and photoelectrochemical properties of the prepared photocatalyst were characterized via a series of characterization techniques. The average fluorescence lifetime of the composite photocatalyst was extended from 6.67 ns to 7.30 ns in comparison with that of g-C3N4, which indicated that the composite photocatalyst enhanced the absorption of visible light and also inhibited the recombination of electron-hole pairs. The mass ratio of MoS2 that corresponded to O-C3N4/MoS2-5 enabled the highest removal rate under simulated sunlight irradiation, which was almost twice that achieved using pure g-C3N4. Relative species scavenging experiments revealed that ·O2 - was the main species during the process of photodegradation. Besides, a toxicity test indicated that glyphosate became less toxic or non-toxic after photodegradation. This study provided an effective, feasible and stable photocatalyst driven by simulated sunlight irradiation for the highly enhanced photodegradation of glyphosate.

Synthesis of g-C3 N4 Nanosheets by Using a Highly Condensed Lamellar Crystalline Melamine-Cyanuric Acid Supramolecular Complex for Enhanced Solar Hydrogen Generation

A highly condensed lamellar melamine-cyanuric acid supramolecular (MCS) complex was synthesized in an autoclave at high pressure as a precursor for preparing g-C₃ N₄ nanosheets. Given the distinctive properties of the prepared MCS complex, an efficient g-C₃ N₄ nanosheet photocatalyst can be obtained by heat treatment of this MCS complex under Ar followed by calcination in air at 400 °C. The resulting nanosheets with in-plane nanoholes showed an extremely high specific surface area (≈270 m²  g^-1 ) and significantly enhanced light absorption in the visible region. This phenomenon is observed for the first time in carbon nitride nanosheets. The enhanced light absorption results from the sizeable conjugated system of tri-striazine units in the carbon nitride framework, coupled with the structural defects arising from the presence of oxygen-containing groups induced during the synthesis. Consequently, the obtained carbon nitride nanosheets exhibited excellent performance for hydrogen generation under sunlight and especially under visible light. Its quantum efficiency (QE) of 20.9 % at 420 nm is one of the highest reported values for carbon nitride materials. A QE of 3.5 % could be observed even at 590 nm. The integrated QE of this material in the visible region (420-600 nm) is approximately 1 %. To the best of our knowledge this is the highest value compared to all other the carbon nitride nanosheet materials reported previously.

Braiding kinetics and spectroscopy in photo-catalysis: the spectro-kinetic approach

The combination of kinetic and spectroscopic tools has become a key scientific methodology for the understanding of catalytic behavior but its application in photocatalysis has inherent difficulties due to the nature of the energy source of the reaction. This review article provides an overview of its use by, first, presenting mechanistically derived kinetic formulations and spectroscopic data handling methods including intrinsic expressions for light and, second, highlighting representative examples of application. To do it we consider universal catalytic systems, particularly (although not exclusively) titania-based materials, and the most frequent hole and/or electron triggered reaction schemes. This review also provides a general framework to pave the way for the future progress of the spectro-kinetic approach in the photocatalysis area.

Performance of PES/LSMM-OGCN Photocatalytic Membrane for Phenol Removal: Effect of OGCN Loading

In designing a photocatalytic oxidation system, the immobilized photocatalyst technique becomes highly profitable due to its promising capability in treating organic pollutants such as phenols in wastewater. In this study, hydrophiLic surface modifying macromolecules (LSMM) modified polyethersulfone (PES) hybrid photocatalytic membranes incorporated with oxygenated graphitic carbon nitride (OGCN) was successfully developed using phase inversion technique. The effectiveness of the hybrid photocatalytic membrane was determined under different loading of OGCN photocatalyst (0, 0.5, 1.0, 1.5, 2.0, and 2.5 wt%). The best amount of OGCN in the casting solution was 1.0 wt% as the agglomeration did not occur considering the stability of the membrane performance and morphology. The highest flux of 264 L/m²·h was achieved by PES/LSMM-OGCN1.5wt% membrane. However, the highest flux performance was not an advantage in this situation as the flux reduced the rejection value due to open pores. The membrane with the highest photocatalytic performance was obtained at 1.0 wt% of OGCN loading with 35.78% phenol degradation after 6 h. Regardless of the lower rejection value, the performance shown by the PES/LSMM-OGCN1.0wt% membrane was still competent because of the small difference of less than 1% to that of the PES/LSMM-OGCN0wt% membrane. Based on the findings, it can be concluded that the optimisation of the OGCN loading in the PES hybrid photocatalytic membrane indeed plays an important role towards enhancing the catalyst distribution, phenol degradation, and acceptable rejection above all considerations.

Ultrasonic irradiation preparation of graphitic-C3N4/polyaniline nanocomposites as counter electrodes for dye-sensitized solar cells

In this research, polyaniline/graphitic carbon nitride (PANI/g-C₃N₄) nanocomposites were synthesized via in-situ electrochemical polymerization of aniline monomer whit different number of cyclic voltammetry scans (10, 20 and 30 cycles) after electrode surface pre-preparation using a potential shock under ultrasonic irradiation. PANI/g-C₃N₄ nanocomposites with two values of g-C₃N₄ (0.010 wt% and 0.015 wt%) were deposited on the surface of the transparent conducting film (FTO glass) by immersing FTO into the aniline solution and g-C₃N₄ during the electro-polymerization. The resulting PANI/g-C₃N₄ films were characterized by Fourier transformed infra-red (FTIR), power X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques. The prepared electrodes were applied as counter electrode in dye-sensitized solar cells. Among them, the prepared electrode with 10 cycles and 0.01 wt% g-C₃N₄ showed the best efficiency. These hybrids show good catalytic activity in elevating tri-iodide reduction and due to the synergistic effect of PANI and g-C₃N₄, PANI/g-C₃N₄ nanocomposite electrode shows power conversion efficiency about 1.8%.

Catalyst-free activation of peroxides under visible LED light irradiation through photoexcitation pathway

Catalysts are known to activate peroxides to generate active radicals (i.e., hydroxyl radical (OH) and sulfate radical (SO₄^-)) under certain conditions, but the activation of peroxides in the absence of catalysts under visible light irradiation has been rarely reported. This work demonstrates a catalyst-free activation of peroxides for the generation of OH and/or SO₄^- through photoexcited electron transfer from organic dyes to peroxides under visible LED light irradiation, where Rhodamine B (RhB) and Eosin Y (EY) were selected as model dyes. The formation of OH and/or SO₄^- in the reactions and the electron transfer from the excited dyes to peroxides were validated via electron paramagnetic resonance (EPR), photoluminescence (PL) spectra and cyclic voltammetry (CV). The performance of the peroxide/dye/Vis process was demonstrated to be altered depending on the target substrate. Meanwhile, the peroxide/dye/Vis process was effective for simultaneous decolorization of dyes and production of active radicals under neutral even or basic conditions. The findings of this study clarified a novel photoexcitation pathway for catalyst-free activation of peroxides under visible light irradiation, which could avoid the secondary metal ion (dissolved or leached) pollution from the metal-based catalysts and expand the application range of the peroxide-based catalytic process.