Synthesis Of Graphitic Carbon Nitride Research Articles

Graphitic Carbon Nitride Doped with the s-Block Metals: Adsorbent for the Removal of Methyl Blue and Copper(II) Ions.

The synthesis of graphitic carbon nitride (g-C3N4) doped with s-block metals is described. The materials were synthesized via thermal polycondensation of cyanamide and the appropriate metal chloride. The inclusion of the metal precursor strongly influenced the surface chemistry features as well as the textural, morphological, and structural properties of the g-C3N4. The doping of g-C3N4with s-block metals markedly enhanced its adsorption performance, which was studied during the removal of two model solutes (methyl blue and copper ions) from aqueous solutions. The maximum adsorption capacity for the organic dye was increased by 680 times after the doping process. The uptake of copper(II) increased ca. 30 times for the doped g-C3N4. The improvement of the adsorption performance is discussed in terms of the surface chemistry and textural features.

In-situ synthesis of graphitic carbon nitride/iron oxide−copper composites and their application in the electrochemical detection of glucose

A simple method was proposed for the synthesis of graphitic carbon nitride (g-C3N4)/iron oxide-copper nanostructures through a one-step pyrolysis of Cu3 [Fe(CN)6]2 and melamine. The iron oxide and copper nanostructures, derived from Cu3 [Fe(CN)6]2, were decorated onto g-C3N4 nanosheets, which can effectively protect the resultant graphitic carbon nitride nanosheets from restacking. The derived Fe2O3 and Cu nanostructures greatly enhance the electro-catalytic property of as-prepared composites. Three components including g-C3N4 nanosheets, Fe2O3 and Cu cooperatively enhance the electrochemical performance of non-enzymatic glucose detection. Modified electrodes based on g-C3N4/Fe2O3-Cu composites could detect glucose in the range of 0.6 μM─2.0 mM with a detection limit of 0.3 μM. The as-fabricated modified electrodes also demonstrated good stability and anti-interference performance.

Role of precursors on photocatalytic behavior of graphitic carbon nitride

Current study is about synthesis of graphitic carbon nitride (g-C3N4) photocatalyst by thermal condensation of various nitrogen rich precursors and their photocatalytic performance towards visible light induced degradation of acid violet 7 dye (AV 7). To understand the effect of precursors on degree of tri-s-triazine ring condensation and its electronic properties, we used different N-rich monomers (e.g. melamine (m), urea (u) and thiourea (t)) and their combinations. The structural, morphological and optical properties of the prepared samples were characterized by powder XRD, SEM and UV-DRS. The photocatalytic degradation of AV 7 (20 mg/L) under visible light irradiation over various g-C3N4 samples have exhibited substantial difference in photocatalytic activity, which is attributed to altered electronic structure and increased surface area. The photocatalytic activity for the degradation of AV7 follows the order: ug-C3N4 >tug-C3N4 >mug-C3N4 >mtug-C3N4 >mg-C3N4 >mtg-C3N4 >tg-C3N4.

Synthesis and photocatalytic properties of graphitic carbon nitride nanofibers using porous anodic alumina templates

In the present study, we describe an effective method for the synthesis of Graphitic carbon nitride (GCN) nanostructures using porous anodic alumina (AAO) membrane as template by simple thermal condensation of cyanamide. Synthesized nanostructure was fully analysed by various techniques to detect its crystalline nature, morphology, luminescent properties followed by the evaluation of its photocatalytic activity in the degradation of Methylene blue dye. Structural analysis of synthesized GCNNF was systematically carried out using x-ray powder diffraction (XRD) and scanning electron microscope (SEM), and. The results confirmed the growth of GCN inside the nanochannels of anodic alumina templates. Luminescent properties of GCNNF were studied using photoluminescence (PL) spectroscopy. PL analysis showed the presence of a strong emission peak in the wavelength range of 350–600 nm in blue region. GCNNF displays higher photocatalytic performance in the photodegradation of methylene blue compare to the bulk GCN.Highlights1. In the present paper, we report the synthesis of graphitic carbon nitride nanofibers (GCNNF) using porous anodic aluminium oxide membranes as templates through thermal condensation of cyanamide at 500 °C.2. The synthesis of Graphitic carbon nitride nanofibers using porous andic alumina template is the efficient approach for increasing crystallinity and surface area.3. The high surface area of graphitic carbon nitride nanofibers has a good impact on novel optical and photocatalytic properties of the bulkGCN.4. AAO templating of GCN is one of the versatile method to produce tailorable GCN nanostructures with higher surface area and less number of structural defects.5. Towards photocatalytic degradation of dyes, the tuning of physical properties is very essential thing hence we are succeeded in achieving better catalytic performance of GCN nanostructures by making use of AAO templates.

Synthesis of graphitic carbon nitride from different precursors by fractional thermal polymerization method and their visible light induced photocatalytic activities

Graphitic carbon nitride(g-C3N4) polymer was successfully synthesized by a fractional thermal polymerization method using melamine, guanidine carbonate and dicyandiamide as precursors. The detailed characterization was carried out by TG-DTG, XRD, SEM, PL, DRS, XPS and BET. The photocatalytic performance was determined by degradation of methyl orange(MO) under visible light irradiation. g-C3N4 obtained from different raw materials and temperature showed different band gap, morphology and photocatalytic activities. The g-C3N4 could be obtained by the polymerization reaction of melamine, guanidine carbonate or dicyandiamide at 515, 550 or 515 °C, respectively. The treatment temperature affected the final properties of the g-C3N4 particles. The g-C3N4-M(melamine, 600 °C), g-C3N4-D(dicyandiamide, 590 °C) and g-C3N4-G (guanidine carbonate, 550 °C) particles showed the best MO degradation photocatalytic performances under visible light irradiation (>400 nm) for 120min.

The facile synthesis of graphitic carbon nitride from amino acid and urea for photocatalytic H2 production

We report on the facile synthesis of g-C3N4 based polymers by co-condensing urea with glycine for photocatalytic hydrogen evolution. The as-prepared photocatalysts were then characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence emission spectrometry, electron paramagnetic resonance spectrometry and transmission electron microscopy. Compared with pristine g-C3N4, obtained from direct pyrolysis of urea, the CNU-G5 photocatalyst showed largely enhanced photocatalytic H2 activities about 75 μmol h−1, which is 5 times higher than of the pristine CNU. The enhanced activities are ascribed to the larger specific area surface, strengthened optical absorption and improved electron transport ability. Our work opens up a new pathway for the synthesis graphitic carbon nitride photocatalysts with glycine modification to enhance photocatalytic activities.

Synthesis of graphitic carbon nitride by heating mixture of urea and thiourea for enhanced photocatalytic H2 production from water under visible light

In this study, the g-C3N4 was prepared by recrystallization and calcining the mixture of urea and thiourea. The obtained samples show high photocatalytic performance for H2 evolution under visible light (λ > 420 nm) irradiation in the presence of triethanolamine as sacrificial reagent. The g-C3N4 was characterized by X-ray diffraction (XRD), nitrogen physisorption, XPS, UV–visible spectroscopy, element analysis (EA), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopic (SEM) and photoluminescence (PL) spectroscopy analysis. The experimental results indicated that the samples derived from the mixture of urea and thiourea contributed to enlarge the specific surface area of g-C3N4 and decrease the recombination of photo-induced electron-hole pairs, consequently enhancing photocatalytic activity. The influence of different mass fraction of thiourea on the H2 evolution rate was explored in the presence of triethanolamine as sacrificial reagent under visible light (λ > 420 nm) irradiation. The photocatalytic results indicated that the sample with optimal photocatalytic activity is derived from the mixture with a thiourea's mass fraction of 2.44%. The optimal H2 evolution rate is 2.60 times and 6.17 times higher than that over g-C3N4 from urea and g-C3N4 from thiourea, respectively.

Controlled synthesis of graphitic carbon nitride and its catalytic properties in Knoevenagel condensations

Graphitic carbon nitride (g-C3N4) with high nitrogen content and surface area was synthesized by the thermal condensation of dicyandiamide and urea. This method gave a much higher product yield than the direct thermal decomposition of urea. The prepared g-C3N4 is active for the Knoevenagel condensation of an aldehyde or ketone with methylenic compounds, but the activity depends on the structure of basic nitrogen species. Fourier transform infrared and X-ray photoelectron spectroscopy show that at least four types of nitrogen species are present in g-C3N4, including primary amines (NH2), secondary amines (NH), tertiary nitrogen (N(C)3), and pyridinic nitrogen (CNC). The amounts and types of these nitrogen species in g-C3N4 are closely related to the urea/dicyandiamide ratio in its precursor mixture. The catalytic activity of these nitrogen species in the inactivated Knoevenagel condensation system decreases in the order of NH2>NH>N(C)3>CNC, while it is similar for the NH2 and NH species in the activated reaction system. This trend provides strong evidence for the abstraction of a proton from the methylenic compounds as the rate-determining step. The prepared g-C3N4 is highly stable and reusable in the Knoevenagel condensation reactions.

High temperature promoted synthesis of graphitic carbon nitride with porous structure and enhanced photocatalytic activity

Graphitic carbon nitride (g-C3N4) was prepared by the polycondensation of melamine at 650 °C for 2 h, then thoroughly characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, elemental analysis, transmission electron microscopy, N2 adsorption–desorption isotherms, UV–Vis diffuse reflectance spectra and photoluminescence spectra. The photocatalytic activity of g-C3N4 catalyst was evaluated by the degradation of Rhodamine B, Methylene blue and phenol solution under visible-light irradiation, which showed that g-C3N4 calcined at 650 °C increased the degree of condensation, thus led to the decreased band gap and exhibited better photocatalytic activity than the reference sample treated at 520 °C and P25. The integrated positive effects of porous structure, larger surface area, stronger visible-light absorption and higher separation efficiency for photoinduced electron–hole pairs over g-C3N4 treated at 650 °C resulted in its improved photocatalytic activity for degrading pollutants. Additionally, the as-prepared g-C3N4 possessed good structural and catalytic stability after three recycles.

Graphitic carbon nitride nanosheets: one-step, high-yield synthesis and application for Cu2+ detection.

In this article we report on the one-step, rapid, high-yield synthesis of graphitic carbon nitride (g-C3N4) nanosheets for the first time. The nanosheets were obtained by pyrolyzing a melamine-KBH4 mixture under Ar. As a fluorosensor for Cu(2+), the g-C3N4 nanosheets exhibit a detection limit as low as 0.5 nM and high selectivity in buffer solutions, and this sensor was applied to the analysis of lake water samples. The electrogenerated chemiluminescence (ECL) behavior of the g-C3N4 nanosheets using Na2S2O8 as the coreactant was also studied. Results suggest that the ECL intensity of the g-C3N4 nanosheets was linear over concentrations of 0-45 nM, with a detection limit of 1.2 nM for Cu(2+).

Facile in situ synthesis of graphitic carbon nitride (g-C3N4)-N-TiO2 heterojunction as an efficient photocatalyst for the selective photoreduction of CO2 to CO

A series of composites of graphitic carbon nitride and in situ nitrogen-doped titanium dioxide (g-C3N4-N-TiO2) were prepared by a simple pyrolysis process of urea and Ti(OH)4. The obtained products were characterized by means of X-ray diffraction, FT-IR transmission spectroscopy, electron microscopy, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, etc. Compared with g-C3N4 and commercial P25, the as-prepared photocatalysts exhibit enhanced photocatalytic performance for photoreduction of CO2 in the presence of water vapor at room temperature. It was found that the mass ratios of urea to Ti(OH)4 in precursors play a role in formation of the composites, and the high ratios of urea to Ti(OH)4 result in the composites of g-C3N4 and N-doped TiO2, while low ratios only result in N-doped TiO2. An interesting selectivity of photocatalytic products displayed that N-doped TiO2 samples were related to CH4 and CO generation, while g-C3N4 and N-TiO2 composites were related to CO generation, and the product selectivity may originate from the formed g-C3N4. The highest amount of CO (14.73μmol) was obtained on the optimized photocatalyst under 12h light irradiation, which is four times of that over commercial P25. Based on these results, a possible mechanism for the enhanced photocatalytic performance was proposed.

Synthesis of graphitic carbon nitride through pyrolysis of melamine and its electrocatalysis for oxygen reduction reaction

Graphitic carbon nitride (g-C3N4) was synthesized via direct pyrolysis of melamine and its electrocatalysis toward oxygen reduction reaction was studied. The morphology and structures of the products were characterized by scanning electron microscope and X-ray powder diffractometer. It was found that higher pyrolysis temperature resulted in more perfect crystalline structure of the graphitic carbon nitride product. Electrochemical characterizations show that the g-C3N4 has electrocatalytic activity toward ORR through a two-step and two-electron process.

Synthesis of graphitic carbon nitride by directly heating sulfuric acid treated melamine for enhanced photocatalytic H 2 production from water under visible light

Herein we report the synthesis of graphitic carbon nitride (g-C 3N 4) by directly heating sulfuric acid treated melamine precursor. Thermoanalytical methods (TG-DSC) in combination with XRD, XPS and elemental analysis were used to characterize the condensation steps of the precursor. The TG-DSC curves clearly show significant difference in thermal behavior between the treated and untreated melamine. The sublimation of melamine during condensation was significantly suppressed by treating melamine with sulfuric acid. The decomposition of melamine sulfuric acid and the condensation of melamine occur simultaneously. The N/C ratio of the prepared carbon nitride (1.53) is slight higher than that of the ideal crystal g-C 3N 4 (1.33), indicating the incomplete condensation of amino groups in the material. The XPS and elemental analysis show that there is no sulfur residue in the final product. The sample synthesized from sulfuric acid treated melamine shows relatively higher BET surface area. The photocatalytic performance of the as prepared carbon nitride was evaluated under visible light irradiation ( λ > 420 nm). The photocatalytic H 2 production rate on sample synthesized from sulfuric acid treated melamine is 2 times higher than that on sample synthesized from untreated melamine.

Synthesis of graphitic carbon nitride by reaction of melamine and uric acid

Graphitic carbon nitrides were synthesized starting from melamine and uric acid. Uric acid was chosen because it thermally decomposes, and reacts with melamine by condensation at temperatures in the range of 400–600 °C. The reagents were mixed with alumina and subsequently the samples were treated in an oven under nitrogen flux. Alumina favored the deposition of the graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in situ chemical vapor deposition (CVD). Infrared (IR) spectra, as well as X-ray diffraction (XRD) patterns, are in accordance with the formation of a graphitic carbon nitride with a structure based on heptazine blocks. These carbon nitrides exhibit poor crystallinity and a nanometric texture, as shown by transmission electron microscopy (TEM) analysis. The thermal degradation of the graphitic carbon nitride occurs through cyano group formation, and involves the bridging tertiary nitrogen and the bonded carbon, which belongs to the heptazine ring, causing the ring opening and the consequent network destruction as inferred by connecting the IR and X-ray photoelectron spectroscopy (XPS) results. This seems to be an easy and promising route to synthesize graphitic carbon nitrides. Our final material is a composite made of an alumina core covered by carbon nitride layers.