Fabrication of highly efficient TiO2/C3N4 visible light driven photocatalysts with enhanced photocatalytic activity

Investigation of TiO2/PPy nanocomposite for photocatalytic applications; synthesis, characterization, and combination with various substrates: a review

The use of photocatalysis technology, specifically visible light photocatalysis that relies on sustainable solar energy, is the most promising for the degradation of contaminants. The interaction of conducting polymer and titanium dioxide (TiO2) leads to the exchange that enhances the alteration of the semiconductor's surface and subsequently decreases the bandgap energy. Polypyrrole (PPy) and TiO2 nanocomposites have promising potential for photocatalytic degradation. Chemically and electrochemical polymerization are two predominant methods for adding inorganic nanoparticles to a conducting polymer host matrix. The most commonly utilized method for producing PPy/TiO2 nanocomposites is the in-situ chemical oxidative polymerization technique. Immobilizing PPy/TiO2 on substrates causes more charge carriers (electron/hole pairs) to be produced on the surface of TiO2 and enhances the rate of photocatalytic degradation compared to pure TiO2. The increased surface charge affects how electron/hole pairs are formed when visible light is used. This study provides a comprehensive investigation into the synthesis, characterization, application, efficiency, and mechanism of PPy/TiO2 nanocomposites in the photocatalytic degradation process of various pollutants. Furthermore, the effect of stabilizing the TiO2/PPy nanocomposite on various substrates will be investigated. In conclusion, the review outlines the ongoing challenges in utilizing these photocatalysts and highlights the essential concerns that require attention in future research. Its objective is to help researchers better understand photocatalysts and encourage their use in wastewater treatment.

Porous graphitic carbon nitride with high concentration of oxygen promotes photocatalytic H2 evolution

Porous structure design and the content regulation of heteroelements have been proved to be effective strategies to boost photocatalytic H₂ generation activity of graphitic carbon nitride (g-C₃N₄) based photocatalyst. Herein, a series of porous graphitic carbon nitride with high concentration of oxygen (g-C₃N₄-O) photocatalysts were synthesized via in situ polymerization process using colloidal SiO₂ as oxygen source. The content of oxygen within the g-C₃N₄-O photocatalysts could be tuned by adjusting the amount of added colloidal SiO₂ during the preparation procedure. The introduced oxygen replaced two-coordinated nitrogen atom, influencing band edge position and localized electron distribution, thereby enhancing visible light harvesting and photoelectric conversion. As a result, the g-C₃N₄-O photocatalyst with an optimal oxygen content (8.39 wt%) showed 10.5 fold enhancement in H₂ evolution rate compared to that of bulk g-C₃N₄, attributed to the porous structure and high concentration of incorporated oxygen.

Au nanoparticles decorated polypyrrole-carbon black/g-C3N4 nanocomposite as ultrafast and efficient visible light photocatalyst

Modification and bandgap engineering are proposed to be extremely significant in improving the photocatalytic activity of novel photocatalysts. The current research focused on the fabrication of ultrafast and efficient visible light-responsive ternary photocatalyst containing g-C₃N₄ nanostructures in conjugation with polypyrrole doped carbon black (PPy-C) and gold (Au) nanoparticles by highly effectual, simple, and straightforward methodology. Various analytical techniques like XRD, FESEM, TEM, XPS, FTIR, and UV-Vis spectroscopy were applied for characterization purposes. The XRD and XPS results confirmed the successful creation of a nanocomposite framework among Au, PPy-C and g-C₃N₄. The TEM images revealed that bare g-C₃N₄ holds sheets or layered graphitic structure with sizes ranging from 100 to 300 nm. The sponge-like PPy-C network intermingled perfectly with g-C₃N₄ sheets along with homogeneously distributed 5-15 nm Au nanoparticles. The band gap energy (E_g) for bare g-C₃N₄, PPy-C/g-C₃N₄ and Au@PPy-C/g-C₃N₄ nanocomposites were found to be 2.74, 2.68, and 2.60 eV, respectively. The photocatalytic activity for all newly designed photocatalysts have been assessed during the degradation of insecticide Imidacloprid and methylene blue (MB) dye, where Au@PPy-C/C₃N₄ was found to be extremely efficient with ultrafast removal of both imidacloprid and MB in just 25 min of visible light irradiation. It was revealed that the Au@PPy-C/g-C₃N₄ ternary photocatalyst removed 96.0% of target analyte imidacloprid, which is ⁓ 2.91 times more efficient than bare g-C₃N₄ in treating imidacloprid. This report provides a distinctly promising, highly effectual and straightforward route to destruct extremely toxic and notorious pollutants and opens a new gateway in the present challenging scenario of environmental concerns.

Heterojunction of N/B/RGO and g-C3N4 anchored magnetic ZnFe2O4@ZnO for promoting UV/Vis-induced photo-catalysis and in vitro toxicity studies

To promote the low photocatalytic efficiency caused by the recombination of electron/hole pairs and widen the photo-response wavelength window, ZnFe₂O₄@ZnO-N/B/RGO and ZnFe₂O₄@ZnO-C₃N₄ ternary heterojunction nanophotocatalysts were designed and successfully prepared through a sol-gel technique. In comparison to bare ZnFe₂O₄ and ZnO, the ZnFe₂O₄-ZnO@N/B/RGO and ZnFe₂O₄@ZnO-C₃N₄ ternary products showed highly improved photocatalytic properties in the degradation of methyl orange (MO) under ultra-violet (UV) and visible light irradiation. Various physicochemical properties of the photocatalysts were evaluated through field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM) techniques. The observations indicated that the ternary heterojuncted ZnFe₂O₄@ZnO-N/B/RGO absorbs lower energy visible light wavelengths, which is an enhancement in the photocatalytic properties of ZnFe₂O₄@ZnO loaded on reduced graphene oxide (RGO) nanosheets and graphite-like carbon nitride (g-C₃N₄). This gives the catalyst photo-Fenton degradation properties.

Soft and hard templates assisted synthesis mesoporous CuO/g-C3N4 heterostructures for highly enhanced and accelerated Hg(II) photoreduction under visible light

Herein, triblock copolymer surfactant (F127) and mesoporous silica (MCM-41) as soft and hard templates were employed to synthesize of mesoporous CuO/g-C₃N₄ heterostructures with large surface areas for Hg(II) photoreduction in existence of formic acid as a holes sacrificial. TEM image for mesoporous CuO/g-C₃N₄ indicated that CuO NPs are homogeneously distributed with spherical shape in particle size ~5 nm onto the surface of g-C₃N₄. Mesoporous 2%CuO/g-C₃N₄ heterostructure was achieved a high Hg(II) photoreduction rate of 628.74 µmolg^-1h^-1 and high photoreduction efficiency of ~100% within 50 min compared with the pure either mesoporous CuO NPs (130.11 µmolg^-1h^-1, 21%) and g-C₃N₄ (88.54 µmolg^-1h^-1, 14%). The highest Hg(II) photoreduction rate achieved was 628.74 µmolg^-1h^-1, which is 4.83 and 7.1 magnitudes stronger than mesoporous CuO NPs and g-C₃N₄. The excellent photocatalytic performance of mesoporous CuO/g-C₃N₄ heterostructures for Hg(II) photoreduction is referred to highly dispersed mesoporous CuO NPs with small particle size onto g-C₃N₄, narrow bandgap, large surface area, a rapid transfer of Hg(II) ions and HCOOH to easily reach the active sites due to the facile penetration through the mesostructure, thus promoting the utilization of porous structure of CuO/g-C₃N₄ heterostructures for efficient diffusion of Hg(II) ions. The intense interaction between mesoporous CuO NPs and porous g-C₃N₄ confirms the durability of the CuO/g-C₃N₄ heterostructures during recyclability for five times.

Solar light harvest: modified d-block metals in photocatalysis

With solar light, modified d-block metal photocatalysts are useful in areas where electricity is insufficient, with its chemical stability during the photocatalytic process, and its low-cost and nontoxicity.

Photocatalytic Applications of Heterostructure Graphitic Carbon Nitride: Pollutant Degradation, Hydrogen Gas Production (water splitting), and CO2 Reduction

Fabrication of the heterojunction composites photocatalyst has attained much attention for solar energy conversion due to their high optimization of reduction-oxidation potential as a result of effective separation of photogenerated electrons-holes pairs. In this review, the background of photocatalysis, mechanism of photocatalysis, and the several researches on the heterostructure graphitic carbon nitride (g-C3N4) semiconductor are discussed. The advantages of the heterostructure g-C3N4 over their precursors are also discussed. The conclusion and future perspectives on this emerging research direction are given. This paper gives a useful knowledge on the heterostructure g-C3N4 and their photocatalytic mechanisms and applications. IMPACT STATEMENTS: The paper on g-C3N4 Nano-based photocatalysts is expected to enlighten scientists on precise management and evaluating the environment, which may merit prospect research into developing suitable mechanism for energy, wastewater treatment and environmental purification.