Fe-Doped g-C3N4: High-Performance Photocatalysts in Rhodamine B Decomposition

Fe-Doped g-C3N4/Bi2MoO6 Heterostructured Composition with Improved Visible Photocatalytic Activity for Rhodamine B Degradation

The binary heterostructured semiconducting visible light photocatalyst of the iron-doped graphitic carbon nitride/bismuth molybdate (Fe-g-C3N4/Bi2MoO6) composite was prepared by coupling with Fe-doped g-C3N4 and Bi2MoO6 particles. In the present study, a comparison of structural characteristics, optical properties, and photocatalytic degradation efficiency and activity between Fe-doped g-C3N4 particles, Bi2MoO6 particles, and Fe-g-C3N4/Bi2MoO6 composite was investigated. The results of X-ray diffraction (XRD) examination indicate that the hydrothermal Bi2MoO6 particles have a single orthorhombic phase and Fourier transform infrared (FTIR) spectroscopy analysis confirms the formation of Fe-doped g-C3N4. The optical bandgaps of the Fe-doped g-C3N4 and Bi2MoO6 particles are 2.74 and 2.73 eV, respectively, as estimated from the Taut plots obtained from UV-Vis diffuse reflectance spectroscopy (DRS) spectra. This characteristic indicates that the two semiconductor materials are suitable for absorbing visible light. The transmission electron microscopy (TEM) micrograph reveals the formation of the heterojunction Fe-g-C3N4/Bi2MoO6 composite. The results of photocatalytic degradation revealed that the developed Fe-g-C3N4/Bi2MoO6 composite photocatalyst exhibited significantly better photodegradation performance than the other two single semiconductor photocatalysts. This property can be attributed to the heterostructured nanostructure, which could effectively prevent the recombination of photogenerated carriers (electron-hole pairs) and enhance photocatalytic activity. Furthermore, cycling test showed that the Fe-g-C3N4/Bi2MoO6 heterostructured photocatalyst exhibited good reproducibility and stability for organic dye photodegradation.

Synthesis of Fe-Modified g-C3N4 Nanorod Bunches for the Efficient Photocatalytic Degradation of Oxytetracycline

Antibiotic residues have been found to have potentially harmful effects on ecological and human health. Carbon nitride-based photocatalysts have widely focused on antibiotic photocatalytic degradation. Herein, we prepared Fe-modified g-C3N4 nanorod bunches (FCNBs) using chemical vapor co-deposition. Specifically, through the process of calcination, a blend of urea and chlorophyllin sodium iron salt underwent an intriguing transformation, resulting in the integration of Fe into the framework of the g-C3N4 nanorod cluster. The resulting photocatalyst exhibited remarkable stability and superior dispersibility. The prepared FCNBs had a unique structure, which was beneficial for increasing light absorption. Furthermore, the Fe species formed a chemical coordination with the g-C3N4 matrix, thereby altering the electronic structure of the matrix. This modification facilitated charge transfer, prolonged the carrier lifetime, and enhanced light absorption, all of which significantly increased the photocatalytic activity. The oxytetracycline degradation efficiency of FCNBs was 82.5%, and they demonstrated outstanding stability in cycle trials. This work introduces a promising photocatalyst for the degradation of antibiotics.

Integrated photocatalysis adsorption processes for oxytetracycline removal: using volborthite and its composite with g-C3N4

The photocatalytic-adsorption performance of the composites of volborthite (CuVA) and graphitic carbon nitride (g-C3N4) was studied in this work using oxytetracycline (OTC) as model pollutant under LED light irradiation. CuVA at different weight percentages (10, 30, 50), namely, C10, C30, and C50, were loaded onto graphitic carbon nitride using wet chemical method. The physical, chemical, and optical properties were evaluated via various analytical techniques. Through integrated adsorption-photocatalytic process, no significant photocatalytic reaction occurred in g-C3N4 and the composite even after 4 h of irradiation. The setup was modified such that each run was conducted in the presence and absence of light. Aside from photolysis and g-C3N4, all composites performed better under the presence of light in which CuVA improved the most from ~ 50% down to ~ 20% of initial concentration. CuVA performed almost identically (80% removal of OTC) under the presence of light irradiation at ambient temperature (22 °C) and in the dark at 32 °C, confirming that temperature was the contributing factor to the improvement instead of light. CuVA exhibited excellent adsorption capacity of 171 mg/g and adsorption rate of 90% towards the removal of highly concentrated OTC (100 mg/L) under optimized parameters of pH 5.0 and at 42 °C after 3 h of adsorption process. Life cycle assessment revealed that close to 50% of fresh 100 ppm OTC could be removed after five cycles without any desorption process.

Transition metals-doped g-C3N4 nanostructures as advanced photocatalysts for energy and environmental applications

Graphitic carbon nitride (g-C3N4)-based heterostructured photocatalysts have received significant attention for its potential applications in the treatment of wastewater and hydrogen evolution. The utilization of semiconductor materials in heterogeneous photocatalysis has recently received great attention due to their potential and eco-friendly properties. Doping with metal ions plays a crucial role in altering the photochemical characteristics of g-C3N4, effectively enhancing photoabsorption into the visible range and thus improving the photocatalytic performance of doped photocatalysts. As an emerging nanomaterial, nanostructured g-C3N4 represents a visible light-active semiconducting photocatalyst that has attracted significant interest in the photocatalysis field, particularly for its practical water treatment applications. To the best of our knowledge, investigations of functionalized photocatalytic (PC) materials on 3d transition metal-doped g-C3N4 remain unexplored in the existing literature. g-C3N4 based heterohybrid photocatalysts have demonstrated excellent reusability, making them highly promising for wastewater treatment applications. This paper describes the overview of numerous studies conducted on the heterostructured g-C3N4 photocatalysts with various 3d metals. Research studies have revealed that the introduction of element doping with various 3d transition metals (e.g., Ti, Mn, Fe, Co, Ni, Cu, Zn, etc.) into g-C3N4 is an efficient approach to enhance degradation efficacy and boost photocatalytic activity (PCA) of doped g-C3N4 catalysts. Moreover, the significance of g-C3N4 heterostructured nanohybrids is highlighted, particularly in the context of wastewater treatment applications. The study concludes by providing insights into future perspectives in this developing area of research, with a specific focus on the degradation of various organic contaminants.

Self-Assembled Synthesis of Porous Iron-Doped Graphitic Carbon Nitride Nanostructures for Efficient Photocatalytic Hydrogen Evolution and Nitrogen Fixation

In this study, Fe-doped graphitic carbon nitride (Fe-MCNC) with varying Fe contents was synthesized via a supramolecular approach, followed by thermal exfoliation, and was then used for accelerated photocatalytic hydrogen evolution and nitrogen fixation. Various techniques were used to study the physicochemical properties of the MCN (g-C₃N₄ from melamine) and Fe-MCNC (MCN for g-C₃N₄ and C for cyanuric acid) catalysts. The field emission scanning electron microscopy (FE-SEM) images clearly demonstrate that the morphology of Fe-MCNC changes from planar sheets to porous, partially twisted (partially developed nanotube and nanorod) nanostructures. The elemental mapping study confirms the uniform distribution of Fe on the MCNC surface. The X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy (UV-DRS) results suggest that the Fe species might exist in the Fe³⁺ state and form Fe-N bonds with N atoms, thereby extending the visible light absorption areas and decreasing the band gap of MCN. Furthermore, doping with precise amounts of Fe might induce exfoliation and increase the specific surface area, but excessive Fe could destroy the MCN structure. The optimized Fe-MCNC nanostructure had a specific surface area of 23.6 m² g^-1, which was 8.1 times greater than that of MCN (2.89 m² g^-1). To study its photocatalytic properties, the nanostructure was tested for photocatalytic hydrogen evolution and nitrogen fixation; 2Fe-MCNC shows the highest photocatalytic activity, which is approximately 13.3 times and 2.4 times better, respectively, than MCN-1H. Due to its high efficiency and stability, the Fe-MCNC nanostructure is a promising and ideal photocatalyst for a wide range of applications.

Metal-Doped Graphitic Carbon Nitride Nanomaterials for Photocatalytic Environmental Applications—A Review

In the current world situation, population and industrial growth have become major problems for energy and environmental concerns. Extremely noxious pollutants such as heavy metal ions, dyes, antibiotics, phenols, and pesticides in water are the main causes behind deprived water quality leading to inadequate access to clean water. In this connection, graphite carbon nitride (GCN or g-C3N4) a nonmetallic polymeric material has been utilized extensively as a visible-light-responsive photocatalyst for a variety of environmental applications. This review focuses on recent developments in the design and photocatalytic applications of metal-doped GCN-based nanomaterials in CO2 photoreduction, water splitting toward hydrogen production, bacterial disinfection, and organic pollutant degradation. Additionally, this review discusses various methods of using GCN-based materials to optimize dye sensitization, metal deposition, ion doping, and their environmental applications.

The Influence of Metal-Doped Graphitic Carbon Nitride on Photocatalytic Conversion of Acetic Acid to Carbon Dioxide

Metal-doped graphitic carbon nitride (MCN) materials have shown great promise as effective photocatalysts for the conversion of acetic acid to carbon dioxide under UV–visible irradiation and are superior to pristine carbon nitride (g-C₃N₄, CN). In this study, the effects of metal dopants on the physicochemical properties of metal-doped CN samples (Fe-, Cu-, Zn-, FeCu-, FeZn-, and CuZn-doped CN) and their catalytic activity in the photooxidation of acetic acid were investigated and discussed for their correlation, especially on their surface and bulk structures. The materials in the order of highest to lowest photocatalytic activity are FeZn_CN, FeCu_CN, Fe_CN, and Cu_CN (rates of CO₂ evolution higher than for CN), followed by Zn_CN, CuZn_CN, and CN (rates of CO₂ evolution lower than CN). Although Fe doping resulted in the extension of the light absorption range, incorporation of metals did not significantly alter the crystalline phase, morphology, and specific surface area of the CN materials. However, the extension of light absorption into the visible region on Fe doping did not provide a suitable explanation for the increase in photocatalytic efficiency. To further understand this issue, the materials were analyzed using two complementary techniques, reversed double-beam photoacoustic spectroscopy (RDB-PAS) and electron spin resonance spectroscopy (ESR). The FeZn_CN, with the highest electron trap density between 2.95 and 3.00 eV, afforded the highest rate of CO₂ evolution from acetic acid photodecomposition. All Fe-incorporated CN materials and Cu-CN reported herein can be categorized as high activity catalysts according to the rates of CO₂ evolution obtained, higher than 0.15 μmol/min⁻¹, or >1.5 times higher than that of pristine CN. Results from this research are suggestive of a correlation between the rate of CO₂ evolution via photocatalytic oxidation of acetic acid with the threshold number of free unpaired electrons in CN-based materials and high electron trap density (between 2.95 and 3.00 eV).

Photocatalytic activation and utilization of CO2 for N-formylation of amines promoted by a zinc(ii) phthalocyanine grafted on g-carbon nitride hybrid

Photochemical conversion of various amines to N-formamides using CO2 under ambient conditions with a hybrid photocatalyst composed of zinc phthalocyanine grafted to g-carbon nitride in high to excellent yields has been described.

Recent advancements of g-C3N4-based magnetic photocatalysts towards the degradation of organic pollutants: a review

Heterogeneous photocatalysis premised on advanced oxidation processes has witnessed a broad application perspective, including water purification and environmental remediation. In particular, the graphitic carbon nitride (g-C₃N₄), an earth-abundant metal-free conjugated polymer, has acquired extensive application scope and interdisciplinary consideration owing to its outstanding structural and physicochemical properties. However, several issues such as the high recombination rate of the photo-generated electron-hole pairs, smaller specific surface area, and lower electrical conductivity curtail the catalytic efficacy of bulk g-C₃N₄. Another challenging task is separating the catalyst from the reaction medium, limiting their reusability and practical applications. Therefore, several methodologies are adopted strategically to tackle these issues. Attention is being paid, especially to the magnetic nanocomposites (NCs) based catalysts to enhance efficiency and proficient reusability property. This review summarizes the latest progress related to the design and development of magnetic g-C₃N₄-based NCs and their utilization in photocatalytic systems. The usefulness of the semiconductor heterojunctions on the catalytic activity, working mechanism, and degradation of pollutants are discussed in detail. The major challenges and prospects of using magnetic g-C₃N₄-based NCs for photocatalytic applications are highlighted in this report.

Electrospun Functional Nanofiber Membrane for Antibiotic Removal in Water: Review

As a new kind of water pollutant, antibiotics have encouraged researchers to develop new treatment technologies. Electrospun fiber membrane shows excellent benefits in antibiotic removal in water due to its advantages of large specific surface area, high porosity, good connectivity, easy surface modification and new functions. This review introduces the four aspects of electrospinning technology, namely, initial development history, working principle, influencing factors and process types. The preparation technologies of electrospun functional fiber membranes are then summarized. Finally, recent studies about antibiotic removal by electrospun functional fiber membrane are reviewed from three aspects, namely, adsorption, photocatalysis and biodegradation. Future research demand is also recommended.