A simple approach for controlling the morphology of g-C3N4 nanosheets with enhanced photocatalytic properties (original) (raw)
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Separation and Purification Technology, 2020
Herein, we report a scalable, green and "bottom-up" approach for the synthesis of ultralight g-C 3 N 4 nanosheets. The ultralight g-C 3 N 4 nanosheets (9.6 mg cm −3) have been entirely synthesized in a wet atmosphere in one step without pretreatment or any other additives. The as-prepared material (UMCN-wet) appears as a foam-like exterior with ultrathin nanosheets (3.5 nm), short-order polymerization and sharp edges. The X-ray diffraction (XRD), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses confirm the formation of melon units with edge-enriched active sites. UMCN-wet exhibits a higher specific surface area (137.44 m 2 g −1) and pore volume (0.2076 cm 3 g −1), compared with that of the as-synthesized materials in the air (MCN-air) and nitrogen (MCN-N 2) atmospheres. The optical and electrochemical analyses reveal that UMCN-wet manifests fast photogenerated charge separation and transfer with slow decay kinetics. As a result, UMCN-wet nanosheets exhibit superb photocatalytic degradation of rhodamine B (RhB), methylene blue (MB) and methyl orange (MO) under visible light irradiation with photodegradation rate constant (k) of 0.17687, 0.02409 and 0.00537 min −1 , respectively. Moreover, UMCN-wet exhibits excellent stability and reusability performance. Such a sustainable approach does not only overcome the prolonged time processing, extra energy consumption and utilization of hazardous chemicals for synthesis ultrathin g-C 3 N 4 nanosheets, but also paves a new pathway for industrial upscale production with numerous expected environmental applications.
Synthesis of g-C3N4 from Various Precursors for Photocatalytic H2 Evolution under the Visible Light
Crystals
Graphitic carbon nitride (g-C3N4) fabricated from different precursors exhibits unique microstructures and photocatalytic performance under visible light. Herein, we synthesized five different microstructures of g-C3N4 by the thermal poly condensation method using guanidine hydrochloride, melamine, urea, dicyandiamide and thiourea as the precursors. The results indicated that g-C3N4 prepared from urea precursor (UCN) has a nanostructure, porous layered structure, large specific surface area, and high separation efficiency of photo generated hole-electron pairs, which showed the best photocatalytic activity among all of the as-prepared samples. As for the lowest cost among the above five precursors, urea is an ideal candidate material for preparing g-C3N4 photocatalyst for a huge potential of wide industrial applications. In addition, Pt or Ni were used as the co-catalyst and loaded onto the g-C3N4 surface for photocatalytic hydrogen production. In comparison with noble metal Pt co-c...
Ag loaded B-doped-g C3N4 nanosheet with efficient properties for photocatalysis
Journal of Environmental Management, 2019
Three material engineering strategies in the form of doping (Boron-doping), nanostructuring (nanosheet (NS) formation) and decorating with plasmonic nanoparticles (loading with Ag metal), were integrated to improve the photocatalytic activity of graphitic carbon nitride (gC 3 N 4). Concentrations of B-doping and Ag-loading were optimized to maximize the catalytic performance in the final nanocomposite of Ag-loaded B-doped gC 3 N 4 NS. Combined effect of all three strategies successfully produced over 5 times higher rate towards degradation of organic dye pollutant when compared to unmodified bulk gC 3 N 4. Detailed characterization results revealed that incorporation of B in gC 3 N 4 matrix reduces the band gap to increase the visible light absorption, while specific surface area is significantly enhanced upon formation of NS. Decoration of Ag nanoparticles (NPs) on B-doped gC 3 N 4 NS assists in fast transfer of photogenerated electrons from gC 3 N 4 to Ag NPs owing to the interfacial electric field across the junctions and thus reduces the recombination process. Investigations on individual strategies revealed that decoration of Ag NPs to induce better charge separation, is the most effective route for enhancing the photocatalytic activity.
Applied Catalysis A: General, 2011
Enhanced photocatalytic degradation of methylene blue (MB) using graphitic carbon nitride/titanium dioxide (g-C 3 N 4 /TiO 2 ) catalyst films has been demonstrated in this present work. The g-C 3 N 4 /TiO 2 composites were prepared by directly heating the mixture of melamine and pre-synthesized TiO 2 nanoparticles in Ar gas flow. The g-C 3 N 4 contents in the g-C 3 N 4 /TiO 2 composites were varied as 0, 20, 50 and 70 wt%. It was found that the visible-light-induced photocatalytic degradation of MB was remarkably increased upon coupling TiO 2 with g-C 3 N 4 and the best degradation performance of $70% was obtained from 50 wt% g-C 3 N 4 loading content. Results from UV-vis absorption study, Electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggest that the improved photoactivity is due to a decrease in band gap energy, an increased light absorption in visible light region and possibly an enhanced electron-hole separation efficiency as a result of effective interfacial electron transfer between TiO 2 and g-C 3 N 4 of the g-C 3 N 4 /TiO 2 composite film. Based on the obtained results, the possible MB degradation mechanism is ascribed mainly to the generation of active species induced by the photogenerated electrons.
A facile and low-cost g-C 3 N 4 surface modification approach using a biomass-derived liquid product is proposed in this work. Through the incorporation of renewable and sustainable bio-oil that is generated from a solar powered waste biomass pyrolysis, the surface functionality of a pristine g-C 3 N 4 material is modified with functional groups that are of electron-withdrawing character, leading to the improvement of the photocatalytic hydrogen evolution rate for the modified C 3 N 4 sample. At low reaction temperature (120 °C), the sample is modified through a cleavage of C-N bonds between three heptazine fragments and tertiary nitrogen, followed by the bonding of oxygenated functional groups. As the reaction temperature increases further to a higher temperature (180 °C), a partial de-aromatization of the triazine network in the C 3 N 4 sample due to the intercalation of functional groups from this post-synthesis bio-oil modification is further observed. The remarkable hydrogen evolution rate of the modified C 3 N 4 sample higher than that of pristine g-C 3 N 4 is observed, attributed to the synergistic effects of the extended visible light response, better separation of the photogenerated charge carriers and the enlarged specific surface area.
Materials Letters, 2019
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Advances in Materials Science and Engineering, 2021
In situ g-C 3 N 4 @ZnO nanocomposites (with 0, 1, 3, 5, and 7 wt.% of g-C 3 N 4 in nanocomposite) were synthesized via a one-pot hydrothermal method using precursors of urea, zinc nitrate hexahydrate, and hexamethylenetetramine. e g-C 3 N 4 @ZnO nanocomposites were characterized by X-ray diffraction, scanning electron microscope, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. e photocatalyst activity of g-C 3 N 4 @ZnO nanocomposites was evaluated via methylene blue degradation experiment under visible light irradiation. e g-C 3 N 4 @ZnO nanocomposites showed an enhancement in photocatalytic activity in comparison to pure ZnO which increased with the g-C 3 N 4 content (1, 3, 5, and 7 wt.%) in nanocomposites. e photocatalytic activity reached the highest efficiency of 96.8% when the content of g-C 3 N 4 was 7.0 wt.%. Nanocomposite having 7.0 wt.% of g-C 3 N 4 also showed good recyclability with degradation efficiency higher than 90% even in the 4 th use. e improvement of photocatalytic activity could be attributed to the adsorption ability and effective separation of electron-hole pairs between g-C 3 N 4 and ZnO. is work implies a simple method to in situ prepare the nanocomposite material of g-C 3 N 4 and semiconductors oxide for photocatalyst applications with high efficiency and good recyclability.
Advanced Powder Technology, 2018
Porous graphitic carbon nitride with a high surface area was successfully synthesized without using any template or other substances like metals, just by placing melamine powder into a muffle furnace which was heated to 550°C in advance. To evaluate the structure, morphology, and optical properties, the high performance g-C 3 N 4 (HPCN) was analyzed by XRD, SEM-EDX, TEM, N 2 physisorption, FT-IR analysis, UV-Vis DRS, PL, and Zeta potential. HPCN was able to completely degrade rhodamine B under visible light with the rate constant of 0.086 min À1 , which is 3.5 times higher than the traditional g-C 3 N 4. The possible mechanism of RhB photodegradation was discussed in detail, which illustrated the reaction is performed in acidic media much better than neutral and basic solutions, and Å O 2 À and h + are the key reactive species during the reaction. Moreover, the stability of the photocatalyst was investigated and turned out its photocatalytic activity has not considerably changed after 6 cycles, so it was a highly stable photocatalyst.
Journal of Metals, Materials and Minerals, 2022
In this study, the g-C3N4/Ag-TiO2 composite photocatalysts were prepared to enhance the efficient utilization of solar energy. The g-C3N4 was synthesized by facile heat treatment of urea at 600℃ for 4 h, and 0.05 wt% to 3 wt% Ag-TiO2 were obtained through the chemical reduction method. The composite photocatalysts were prepared by mixing the g-C3N4 and Ag-TiO2 with a weight ratio of 50:50 at room temperature. The photocatalytic efficiency was carried out by using 0.05 g of photocatalysts with 10 mg•L-1 of rhodamine B 120 mL under 60 min of visible light irradiation. The experimental results indicated that a sample with 0.1 wt% Ag-TiO2 could degrade rhodamine B up to 21.21%. The g-C3N4/(0.1 wt% Ag-TiO2) and g-C3N4 showed rhodamine B degradation efficiency up to 100%, which was 10.4 times and 4.7 times of pure TiO2 and 0.1 wt% Ag-TiO2, respectively. It can be suggested that the Ag deposited on TiO2 played an important role in the absorption capability under the visible light through the surface plasmon resonance effect. In addition, heterojunction between g-C3N4 and TiO2 could reduce the recombination of electron-hole pairs.