Search Results (47)

Nanomaterials with large specific surface area (SSA) have emerged as pivotal platforms for energy storage and environmental remediation, primarily due to their enhanced active site exposure, improved mass transport capabilities, and superior interfacial reactivity. Among them, polymeric carbon nitride (g-C₃N₄) has garnered significant attention in energy and environmental applications owing to its visible-light-responsive bandgap (~2.7 eV), exceptional thermal/chemical stability, and earth-abundant composition. However, the practical performance of g-C₃N₄ is fundamentally constrained by intrinsic limitations, including its inherently low SSA (<20 m²/g via conventional thermal polymerization), rapid recombination of photogenerated carriers, and inefficient charge transfer kinetics. Notably, the theoretical SSA of g-C₃N₄ reaches 2500 m²/g, yet achieving this value remains challenging due to strong interlayer van der Waals interactions and structural collapse during synthesis. Recent advances demonstrate that state-of-the-art strategies can elevate its SSA to 50–200 m²/g. To break this surface area barrier, advanced strategies achieve SSA enhancement through three primary pathways: pre-treatment (molecular and supramolecular precursor design), in process (templating and controlled polycondensation), and post-processing (chemical exfoliation and defect engineering). This review systematically examines controllable synthesis methodologies for high-SSA g-C₃N₄, analyzing how SSA amplification intrinsically modulates band structures, extends carrier lifetimes, and boosts catalytic efficiencies. Future research should prioritize synergistic multi-stage engineering to approach the theoretical SSA limit (2500 m²/g) while preserving robust optoelectronic properties. Full article

The degradation of pharmaceuticals in wastewater treatment plants (WWTPs), particularly the antidepressant Paroxetine (PXT), is a growing concern because their insufficient removal leads to their release in the aquatic environment, causing toxic effects on aquatic organisms. This study investigates g-C₃N₄ materials synthesized from urea, melamine, and thiourea, including thermally exfoliated variants, as potential photocatalysts for removing PXT from water and secondary-treated hospital wastewater (HWW). Comparative photocatalytic experiments under simulated solar radiation indicated that g-C₃N₄ prepared by urea (CN-U) and its thermally exfoliated form [CN-U(exf.)] were highly effective (100% removal in 45 min) depending on the degradation rate constants (0.036 and 0.085 min⁻¹ in U.P. water, respectively), with the latter achieving the fastest PXT degradation at 200 mg/L (k = 0.112 min⁻¹). The study also analyzed mineralization and transformation products (TPs) using liquid chromatography–high-resolution mass spectrometry (LC–HR-MS-Orbitrap) and assessed their ecotoxicity with ECOSAR (Version 2.2) software. Additionally, toxicity decreased following the photocatalytic processes, as revealed by the Microtox bioassay. Overall, CN-U and especially CN-U(exf.) show promise as eco-friendly photocatalysts for pharmaceutical removal from wastewater (WW). Full article

The scattering of reinforcement plays a crucial role in the microstructure and properties of metal matrix composites. In this study, an aluminum matrix composite (AMC) was reinforced by 10 wt% TiO₂ (Al-10TiO₂), with an average particle size of a submicron, combined with a different content of graphitic carbon nitride (g-C₃N₄), which was fabricated by shift-speed ball milling (SSBM) combined with multi-pass friction stir processing (FSP). In addition to the high hardness of TiO₂, g-C₃N₄ has functional groups to promote in situ reactions. SSBM improves the distribution of reinforcement, refines grain size, and reduces the structural destruction of g-C₃N₄. The in situ reaction was achieved after multi-pass FSP at a high rotational speed and low travel speeds, which can promote uniform dispersion and grain refinement. Moreover, the g-C₃N₄ shows the efficient enhancement of strength while maintaining the elongation of AMC. Because the exfoliation of g-C₃N₄ under the effect of processing reduces the agglomeration of TiO₂, boosts the flattening of Al, and enhances interface integration with the base metal. In situ phases can reduce the generation of coarse phases and improve interfacial bonding ability to enhance mechanical properties. The maximum tensile strength has been found at about 172.5 MPa in the Al-10TiO₂ containing 1 wt% g-C₃N₄, which was enhanced by 34% compared to that of the Al-10TiO₂. The tensile strength increases when the g-C₃N₄ content increases from 0 to 1 wt%, but then reduces with a further increase of content. The hardness was increased by 50.2%, 60.2%, and 35% with a g-C₃N₄ content of 0.5, 1, and 2 wt% compared to AMCs without reinforcement, respectively. According to the test, the enhancement mechanism is mainly attributed to Orowan, grain refinement strengthening, and load transfer of scattered reinforcement. In summary, the utilization of hybrid reinforcements successfully enhances the microstructure and mechanical properties. Full article

This study presents the development of flexible piezoelectric nanogenerators (PENGs) utilizing graphitic carbon nitride (g-C₃N₄) nanoflakes (CNNFs) and polyvinylidene fluoride (PVDF) composites fabricated via the direct ink writing (DIW) 3D printing method. A novel approach of synthesizing CNNFs using the ethanol exfoliation method was demonstrated, which significantly reduces preparation time and cost compared to traditional acid exfoliation. The CNNFs are incorporated into PVDFs at varying weight percentages (5, 7.5, 10, and 15 wt.%) to optimize the β-phase content and piezoelectric properties. Characterization techniques including XRD, FTIR, and FESEM confirm the successful synthesis and alignment of nanoflakes inside the PVDF matrix. The film with 7.5% CNNF achieves the highest performance, exhibiting a peak output voltage of approximately 6.5 V under a 45 N force. This study also explores the effects of UV light exposure. Under a UV light, the film exhibits an output voltage of 8 V, indicating the device’s durability and potential for practical applications. The fabricated device showed significant voltage outputs during various human motions, confirming its suitability for wearable self-powered IoT applications. This work highlights the efficacy of the ethanol exfoliation method and the DIW printing technique in enhancing the performance of flexible PENGs. Full article

Photocatalytic H₂ evolution has been regarded as a promising technology to alleviate the energy crisis. Designing graphitic carbon nitride materials with a large surface area, short diffusion paths for electrons, and more exposed reactive sites are beneficial for hydrogen evolution. In this study, a facile method was proposed to dope P into a graphitic carbon nitride framework by calcining melamine with 2-aminoethylphosphonic acid. Meanwhile, PCN nanosheets (PCNSs) were obtained through a thermal exfoliation strategy. Under visible light, the PCNS sample displayed a hydrogen evolution rate of 700 μmol·g⁻¹·h⁻¹, which was 43.8-fold higher than that of pure g-C₃N₄. In addition, the PCNS photocatalyst also displayed good photostability for four consecutive cycles, with a total reaction time of 12 h. Its outstanding photocatalytic performance was attributed to the higher surface area exposing more reactive sites and the enlarged band edge for photoreduction potentials. This work provides a facile strategy to regulate catalytic structures, which may attract great research interest in the field of catalysis. Full article

Graphitic carbon Nitride (g-C₃N₄) is one of the most utilized graphitic materials in hydrogen (H₂) production via photocatalytic water splitting. Thus, a detailed critical overview, updated with the most recent works, has been performed on the synthesis methods, modification techniques, characterization, and mechanisms of g-C₃N₄ and g-C₃N₄-based composite materials, with the aim of clarifying the optimum course towards highly efficient hydrogen-producing photocatalysts based on this promising material. First, the synthesis methods for different morphologies of pure g-C₃N₄ (bulk, nanosheets, nanotubes and nanodots) are critically analyzed in detail for every step and parameter involved, with special mention regarding the modification methods of g-C₃N₄ (doping and composite formation). Next, the most common results of g-C₃N₄ characterization, regarding structural, morphological, optical, and electrical properties, are presented and analyzed. Then, a detailed critical survey of the mechanisms, using g-C₃N₄ and g-C₃N₄-based composites during photocatalytic activity, is performed with a focus on their effect on their hydrogen production capabilities via water splitting. This review aims to provide a clear image of all aspects regarding the use of g-C₃N₄ for photocatalysis, as well as a comprehensive guide for research targeted towards this promising graphitic material. Full article

In the last few years, increasing interest from researchers and companies has been shown in the development of photocatalytic coatings for air purification and self-cleaning applications. In order to maintain the photocatalyst’s concentration as low as possible, highly active materials and/or combinations of them are required. In this work, novel photocatalytic formulations containing g-C₃N₄/TiO₂ composites were prepared and deposited in the form of coatings on a-block substrates. The obtained photocatalytic surfaces were tested for NOx and acetaldehyde removal from model air. It was found that the addition of only 0.5 wt% g-C₃N₄ towards TiO₂ content results in over 50% increase in the photocatalytic activity under visible light irradiation in comparison to pure TiO₂ coating, while the activity under UV light was not affected. The result was related to the creation of a g-C₃N₄/TiO₂ heterojunction that improves the light absorption and the separation of photogenerated electron-hole pairs, as well as to the inhibition of TiO₂ particles’ agglomeration due to the presence of g-C₃N₄ sheets. Full article

The catalytic oxidation of alcohols is an important transformation in the chemical industry. Carbon materials with a large surface area and N doping show great promise as metal-free catalysts for the reaction. In this study, a rich N-containing covalent triazine framework polymerized by cyanuric chloride and p-phenylenediamine was used to synthesize N-doped porous carbon with the assistance of a pore-forming agent—NaCl. First, the mass ratio of the polymer/NaCl was optimized to 1:9. Then, the influence of the pyrolysis temperatures (700–1000 °C) on the materials was studied in detail. It was found that the carbon materials were gradually exfoliated by molten salt at high temperatures. XRD and Raman characterizations showed them with a certain graphitization. The optimal doped carbon CNN-1-9-900 achieved the highest surface area of 199.03 m²g⁻¹ with the largest pore volume of 0.29 cm³g⁻¹. Furthermore, it had a high N content of 9.9 at% with the highest relative proportion of pyridinic/graphitic N. Due to the synergistic effect between the surface area and pyridinic/graphitic N, CNN-1-9-900 showed the best performance for benzyl alcohol oxidation with TBHP at moderate conditions, and the process also worked for its derivatives. Full article

The limited access to fresh water and the increased presence of emergent pollutants (EPs) in wastewater has increased the interest in developing strategies for wastewater remediation, including photocatalysis. Graphitic carbon nitride (g-C₃N₄) is a 2D non-metal material with outstanding properties, such as a 2.7 eV bandgap and physicochemical stability, making it a promising photocatalyst. This work reports the process of obtaining high-surface-area (SA) g-C₃N₄ using the thermal-exfoliation process and the posterior effect of Ag-nanoparticle loading over the exfoliated g-C₃N₄ surface. The photocatalytic activity of samples was evaluated through methylene blue (MB) degradation under visible-light radiation and correlated to its physical properties obtained by XRD, TEM, BET, and UV–Vis analyses. Moreover, 74% MB degradation was achieved by exfoliated g-C₃N₄ compared to its bulk counterpart (55%) in 180 min. Moreover, better photocatalytic performances (94% MB remotion) were registered at low Ag loading, with 5 wt.% as the optimal value. Such an improvement is attributed to the synergetic effect produced by a higher SA and the role of Ag nanoparticles in preventing charge-recombination processes. Based on the results, this work provides a simple and efficient methodology to obtain Ag/g-C₃N₄ photocatalysts with enhanced photocatalytic performance that is adequate for water remediation under sunlight conditions. Full article

Graphitic carbon nitride (g-C₃N₄) is a metal-free photocatalyst used for visible-driven hydrogen production, CO₂ reduction, and organic pollutant degradation. In addition to the most attractive feature of visible photoactivity, its other benefits include thermal and photochemical stability, cost-effectiveness, and simple and easy-scale-up synthesis. However, its performance is still limited due to its low absorption at longer wavelengths in the visible range, and high charge recombination. In addition, the exfoliated nanosheets easily aggregate, causing the reduction in specific surface area, and thus its photoactivity. Herein, we propose the use of ultra-thin porous g-C₃N₄ nanosheets to overcome these limitations and improve its photocatalytic performance. Through the optimization of a novel multi-step synthetic protocol, based on an initial thermal treatment, the use of nitric acid (HNO₃), and an ultrasonication step, we were able to obtain very thin and well-tuned material that yielded exceptional photodegradation performance of methyl orange (MO) under visible light irradiation, without the need for any co-catalyst. About 96% of MO was degraded in as short as 30 min, achieving a normalized apparent reaction rate constant (k) of 1.1 × 10⁻² min⁻¹mg⁻¹. This represents the highest k value ever reported using C₃N₄-based photocatalysts for MO degradation, based on our thorough literature search. Ultrasonication in acid not only prevents agglomeration of g-C₃N₄ nanosheets but also tunes pore size distribution and plays a key role in this achievement. We also studied their performance in a photocatalytic hydrogen evolution reaction (HER), achieving a production of 1842 µmol h⁻¹ g⁻¹. Through a profound analysis of all the samples’ structure, morphology, and optical properties, we provide physical insight into the improved performance of our optimized porous g-C₃N₄ sample for both photocatalytic reactions. This research may serve as a guide for improving the photocatalytic activity of porous two-dimensional (2D) semiconductors under visible light irradiation. Full article

Graphitized carbon nitride (g-C₃N₄), as a metal-free, visible-light-responsive photocatalyst, has a very broad application prospect in the fields of solar energy conversion and environmental remediation. The g-C₃N₄ photocatalyst owns a series of conspicuous characteristics, such as very suitable band structure, strong physicochemical stability, abundant reserves, low cost, etc. Research on the g-C₃N₄ or g-C₃N₄-based photocatalysts for real applications has become a competitive hot topic and a frontier area with thousands of publications over the past 17 years. In this paper, we carefully reviewed the recent advances in the synthesis and structural design of g-C₃N₄ materials for efficient photocatalysts. First, the crucial synthesis parameters of g-C₃N₄ were fully discussed, including the categories of g-C₃N₄ precursors, reaction temperature, reaction atmosphere and reaction duration. Second, the construction approaches of various nanostructures were surveyed in detail, such as hard and soft template, supramolecular preorganization and template-free approaches. Third, the characteristics of different exfoliation methods were compared and summarized. At the end, the problems of g-C₃N₄ materials in photocatalysis and the prospect of further development were disclosed and proposed to provide some key guidance for designing more efficient and applicable g-C₃N₄ or g-C₃N₄-based photocatalysts. Full article

New heterojunction materials (HJs) were synthesized in-situ by molecularly bonding the monomers of a triazine-based covalent organic framework (bulk COF) on the template of exfoliated carbon nitride (g-C₃N₄). The photocatalysts reduced carbon dioxide to carbon monoxide in aqueous dispersions under UV irradiation. The g-C₃N₄ showed production of 6.50 $\mathsf{\mu }$mol CO g⁻¹ h⁻¹ and the bulk COF of 2.77 $\mathsf{\mu }$mol CO g⁻¹ h⁻¹. The CO yield was evaluated in sustainability photoreduction cycles and their CO₂ uptake capacity and isosteric heat of adsorption were estimated. All the heterojunction photocatalysts obtained ameliorated CO production rates compared to the bulk COF. Finally, the influence of the Pt co-catalyst on the photocatalytic activities was determined without the addition of any sacrificial agent, and the COF:g-C₃N₄ heterojunction with the ratio of 1:10 was proven to be a photocatalytic system with an optimum and selective, CO yield of 7.56 $\mathsf{\mu }$mol g⁻¹ h⁻¹. Full article

As a typical organic semiconductor photocatalyst, graphitic carbon nitride (g-C₃N₄) suffers from low photocatalytic activity. In this paper, g-C₃N₄ was prepared by polymerization of dicyandiamide (C₂H₄N₄) in the presence of ammonium chloride (NH₄Cl). It was found that the addition of ammonium chloride can greatly improve the photocatalytic activity of g-C₃N₄ towards CO₂ reduction. The optimal photocatalyst (CN-Cl 20) exhibited a CO₂-to-CO conversion activity of 50.6 μmolg⁻¹h⁻¹, which is 3.1 times that of pristine bulk g-C₃N₄ (BCN) that was prepared in the absence of any ammonium chloride. The enhanced photoactivity of g-C₃N₄ was attributed to the combined effects of chloride modification and an enlarged specific surface area. Chloride modification of g-C₃N₄ can not only reduce the bandgap, but also causes a negatively shifted conduction band (CB) potential level, while ammonia (NH₃) gas from the decomposition of NH₄Cl can act as a gas template to exfoliate layered structure g-C₃N₄, improving the specific surface from 6.8 to 21.3 m²g⁻¹. This study provides new ideas for the synthesis of highly efficient g-C₃N₄-based photocatalytic materials for CO₂ conversion and utilization. Full article

Solar energy harvesting using semiconductor photocatalysis offers an enticing solution to two of the biggest societal challenges, energy scarcity and environmental pollution. After decades of effort, no photocatalyst exists which can simultaneously meet the demand for excellent absorption, high quantum efficiency and photochemical resilience/durability. While CdS is an excellent photocatalyst for hydrogen evolution, pollutant degradation and organic synthesis, photocorrosion of CdS leads to the deactivation of the catalyst. Surface passivation of CdS with 2D graphitic carbon nitrides (CN) such as g-C₃N₄ and C₃N₅ has been shown to mitigate the photocorrosion problem but the poor oxidizing power of photogenerated holes in CN limits the utility of this approach for photooxidation reactions. We report the synthesis of exfoliated 2D nanosheets of a modified carbon nitride constituted of tris-s-triazine (C₆N₇) linked pyromellitic dianhydride polydiimide (CN:PDI) with a deep oxidative highest occupied molecular orbital (HOMO) position, which ensures sufficient oxidizing power for photogenerated holes in CN. The heterojunction formed by the wrapping of mono-/few layered CN:PDI on CdS nanorods (CdS/CN:PDI) was determined to be an excellent photocatalyst for oxidation reactions including photoelectrochemical water splitting, dye decolorization and the photocatalytic conversion of benzyl alcohol to benzaldehyde. Extensive structural characterization using HR-TEM, Raman, XPS, etc., confirmed wrapping of few-layered CN:PDI on CdS nanorods. The increased photoactivity in CdS/CN:PDI catalyst was ascribed to facile electron transfer from CdS to CN:PDI in comparison to CdS/g-C₃N₄, leading to an increased electron density on the surface of the photocatalyst to drive chemical reactions. Full article

Exfoliated g-C₃N₄ is a well-known semiconductor utilized in heterogenous photocatalysis and water splitting. An improvement in light harvesting and separation of photogenerated charge carriers may be obtained by polymer doping with sulfur. In this work, we incorporate sulfur into the polymer chain by chemical polymerization of trithiocyanuric acid (C₃N₃S₃H₃) to obtain C₃N₃S₃. The XRD measurements and TEM images indicated that C₃N₃S₃, in contrast to g-C₃N₄, does not exist in the form of a graphitic structure and is not exfoliated into thin lamellas. However, both polymers have similar optical properties and positions of the conduction and valence bands. The comparative studies of electrochemical oxygen reduction and hydrogen evolution indicated that the overpotentials for the two processes were smaller for C₃N₃S₃ than for g-C₃N₄. The RDE experiments in the oxygen-saturated solutions of 0.1 M NaOH have shown that O₂ is electrochemically reduced via the serial pathway with two electrons involved in the first step. The spectroscopic experiments using NBT demonstrated that both polymers reveal high activity in the photocatalytic reduction of oxygen to superoxide anion radical by the photogenerated electrons. Full article