g-C3N4 Composites Research Articles

Fabrication of g-C3N4/TiO2 hierarchical spheres with reactive {001} TiO2 crystal facets and its visible-light photocatalytic activity

Graphitic carbon nitride (g-C3N4) is a fascinating polymeric organic semiconductor and has attracted extensive interests from researchers during the past few decades. This work focused on a g-C3N4/TiO2 composite with high percentage of {001} facets. We confirmed that composites of g-C3N4/TiO2 with close interfacial connections between g-C3N4 and TiO2 had been formed and made up of reactive {001} TiO2 crystal facets. It also presented significantly enhanced photocatalytic ability toward to RhB degradation, gaseous acetone photoconversion and hydrogen evolution under visible light irradiation. Active species trapping experiments indicated that O2− played a most important part in catalytic process. It was also pointed out that the enhanced photocatalytic efficiency could be attributed to the interfacial connections between g-C3N4 and TiO2, which efficiently transferred the photocarriers.

G-C3N4/conductive carbon black composite as Pt-free counter electrode in dye-sensitized solar cells

The composites of g-C3N4 and conductive carbon black (CCB) were prepared by a simple ball-milling process and explored as the counter electrode for dye-sensitized solar cells (DSCs). The enhanced electrocatalytic activity for I3− reduction can be demonstrated when CCB was incorporated into g-C3N4. The charge-transfer resistance of g-C3N4/CCB (1:1, mass ratio) composite electrode was 2.4Ωcm2, which is much lower than those of the individual g-C3N4 and CCB electrodes, indicating predominant synergistic effect of g-C3N4 and CCB in electrocatalytic activity. Under illumination of 100mWcm−2, the DSC with g-C3N4/CCB (1:1) composite counter electrode achieved a conversion efficiency of 5.09%, which is comparable to that of the cell with Pt counter electrode.

ZIF-8 derived carbon (C-ZIF) as a bifunctional electron acceptor and HER cocatalyst for g-C3N4: construction of a metal-free, all carbon-based photocatalytic system for efficient hydrogen evolution

A ZIF-8 derived carbon (C-ZIF)/g-C3N4 composite was constructed for the first time and it displayed highly enhanced photocatalytic H2 evolution performance.

Graphitic carbon nitride as a photovoltaic booster in quantum dot sensitized solar cells: a synergistic approach for enhanced charge separation and injection

A binary hybrid composite of g-C3N4 and ZnO is introduced as a photoanodic material in QDSSC devices and ∼70% improvement in power conversion efficiency is achieved.

In-situ fabrication of Ag/g-C3N4 composite materials with improved photocatalytic activity by coordination-driven assembly of precursors

The incorporation of noble metals into semiconductors has been proven to be effective for the construction of highly efficient composite photocatalytic systems. In this work, the Ag/graphitic carbon nitride (g-C3N4) composite was in-situ fabricated by combining the coordination-driven assembly of precursors and calcination process. The interactions between precursors favor the formation of well-defined rod-like Ag-containing complex intermediates, the subsequent annealing of the obtained intermediates produces the Ag/g-C3N4 composite catalysts with improved photodegradation of rhodamine B (RhB). Although the composite differs in the morphology and nitrogen-containing precursor, the role of generated Ag component in the Ag/g-C3N4 composite is considered to be crucial for the enhancement both in light-harvesting ability and photocatalytic activity owing to its unique surface plasmonic effects. Holes and radicals trapping experiments imply that photo-induced active holes and superoxide radicals are predominant under visible light irradiation and make major contributions to improved photocatalytic performance. The finding provides an opportunity to design and in-situ synthesize noble metal-doped semiconductor heterojunctions for potential applications in photocatalysis, photovoltaic and photoelectronic devices.

Hydrothermal synthesis of α-Fe2O3/g-C3N4 composite and its efficient photocatalytic reduction of Cr(VI) under visible light

α-Fe2O3/g-C3N4 composites were fabricated by a facile hydrothermal method. The prepared composites were characterized by XRD, XPS, TEM, DRS, PL and photoelectrochemical measurement. Under visible light irradiation, α-Fe2O3/g-C3N4 composite displays higher photocatalytic activity than pure g-C3N4 and α-Fe2O3 for Cr(VI) reduction. The enhanced photocatalytic activity should be attributed to the well-matched band structure and intimate contact interfaces between g-C3N4 and α-Fe2O3, which lead to the effective transfer and separation of the photogenerated charge carriers. The decoration of α-Fe2O3 does not affect the morphology and size of g-C3N4. The lower photoluminescence intensity and higher photocurrent density indicate the effective transfer and separation of photogenerated charge carriers. α-Fe2O3/g-C3N4 composite shows more intense optical absorption compared with pure g-C3N4. The addition of hole scavengers can greatly facilitate the photocatalytic reduction of Cr(VI) and the α-Fe2O3/g-C3N4 composite shows excellent stability during the photocatalytic reduction of Cr(VI).

Au/PtO nanoparticle-modified g-C3N4 for plasmon-enhanced photocatalytic hydrogen evolution under visible light

Photocatalytic hydrogen evolution under visible light is of great potential for renewable energy development. In this work, unalloyed Au/PtO nanoparticle (NP) co-modified graphitic carbon nitride (g-C3N4) photocatalyst is fabricated through a simple photodeposition method. The obtained g-C3N4 composites with co-existed Au and PtO cocatalysts exhibit a considerable enhancement in the photocatalytic hydrogen evolution activity and possess good stability during cycling experiments. The optimal Au–PtO/g-C3N4 photocatalyst shows a H2 production rate of 16.9μmolh−1, which exceeds that of PtO/g-C3N4 and Au/g-C3N4 by a factor of 1.5 and 10.6, respectively. Further characterizations demonstrate that the synergetic action of electron-sink and catalytic effects of PtO along with surface plasmon resonance (SPR) effect of Au NPs, greatly improves the photocatalytic performance of g-C3N4 under visible light. Our study should bring in new insight into the design of effective g-C3N4-based photocatalysts for solar-to-fuel conversion.

Enhanced visible light photocatalytic H2-production of g-C3N4/WS2 composite heterostructures

As a clean and renewable solar H2-production system to address the increasing global environmental crisis and energy demand, photocatalytic hydrogen production from water splitting using earth abundant materials has received a lot of attention. In this study, WS2-graphitic carbon nitride (g-C3N4) composites were prepared using WO3 and thiourea as precursors through a gas–solid reaction. Different amount of WS2 were loaded on g-C3N4 to form the heterostructures and the composite samples exhibited enhanced photocatalytic activity for H2 production under visible light. The composite sample with 0.01wt% WS2 exhibited the highest H2-production rate of 101μmolg−1h−1, which was even better than that of the Pt-C3N4 sample with the same loading content. The high photocatalytic activity was attributed to the formation of heterojunction between g-C3N4 and WS2 cocatalyst which allowed for effective separation of photogenerated charge carriers. This work showed the possibility for the utilization of low cost WS2 as an efficient cocatalyst to promote the photocatalytic H2 production of g-C3N4.

Synthesis of g-C3N4/CeO2 nanocomposites with improved catalytic activity on the thermal decomposition of ammonium perchlorate

Novel g-C3N4/CeO2 nanocomposites were synthesized through a simple mixing-calcination method. The structure, morphology and composition of g-C3N4/CeO2 nanocomposites were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), as well as X-ray photoelectron spectroscopy (XPS). The results indicated that CeO2 nanoparticles with a diameter of 50–100nm were uniformly loaded on the surface of g-C3N4. Furthermore, the catalytic effect of our prepared novel g-C3N4/CeO2 nanocomposites on the thermal decomposition of ammonium perchlorate (AP) was investigated by utilizing thermogravimetric and differential thermal analyses (TG-DTA). Compared with pure g-C3N4 and CeO2, the g-C3N4/CeO2 nanocomposites were proved to catalyze the thermal decomposition of AP more effectively. Upon addition of g-C3N4/CeO2 nanocomposites, the high weight-loss decomposition temperature of AP was decreased by up to 74.6°C, which is quite more than that upon the addition of pure g-C3N4 and CeO2. The proposed mechanism demonstrated that this situation was presumably attributed to a synergistic effect between g-C3N4 and CeO2.

Enhanced visible light-driven photocatalytic performance of ZnO–g-C3N4 coupled with graphene oxide as a novel ternary nanocomposite

This article reports a novel ternary nanocomposite consisting of ZnO, g-C3N4, and graphene oxide (GO) that provides enhanced photocatalytic performance and stability. The ZnO nanospheres disperse evenly and embed themselves in the porous g-C3N4. Composites with various g-C3N4 and GO to ZnO weight ratios were synthesized and characterized systematically. The results indicated that the absorption of binary g-C3N4/ZnO nanocomposites shifted to a lower energy compared to pure ZnO in a fashion consistent with the loading content of g-C3N4. Notably, the loading content of GO in the ZnO–g-C3N4 composite resulted in increased absorption in the visible range and improved charge separation efficiency, thereby drastically improving photocatalytic activity. Successful hybridization of ternary nanocomposite was confirmed by drastic quenching of fluorescence and broader visible light absorption. The optimal content of g-C3N4 in the ZnO–g-C3N4 composite was 50%, which exhibited the effective hybridization between ZnO and g-C3N4, and high photocatalytic efficiency. However, the photocatalytic degradation of the ternary nanocomposite showed performance that was two times greater than ZnO–g-C3N4, exhibiting 99.5% degradation efficiency after just 15min of light irradiation. The combined heterojunction and synergistic effects of this composite account for the improved photocatalytic activity.

Synthesis of TiO2/g-C3N4 nanocomposites as efficient photocatalysts dependent on the enhanced photogenerated charge separation

We have synthesized different mass ratios of effectively-contacted TiO2/bulk g-C3N4 composites (T/CN) by a wet chemical method, and evaluated their photocatalytic activities for degrading acetaldehyde and producing H2. It is clearly demonstrated by means of surface photovoltage responses and photoluminescence spectra that the photogenerated charge carriers in the T/CN nanocomposites with a proper mass ratio of T display much higher separation in comparison to CN alone. This is well responsible for the enhanced photocatalytic activities of CN after coupling with nanocrystalline anatase TiO2. Interestingly, it is also applicable to the resulting CN nanosheet (about 3nm) with higher photoactivity than the bulk one. As a result, the TiO2/CN-nanosheet composites as efficient photocatalysts have been successfully developed. Moreover, it is confirmed that the enhanced photoactivity for resulting nanocomposites are attributed to the promoted charge transfer and separation from CN to TiO2.

Synthesis of Ordered Mesoporous Carbon/Graphitic Carbon Nitride (g-C3N4) Composites with Enhanced Visible-light-driven Photocatalytic Activity

Abstract In this paper, ordered mesoporous carbon (OMC)/graphitic carbon nitride (g-C3N4) composites were synthesized by a simple low-temperature thermal method. The structural properties of the OMC/g-C3N4 composites were characterized by XRD, N2 adsorption–desorption isotherms, and UV–vis diffuse reflectance spectroscopy. It was found that the addition of OMC slightly affected the graphitic stacking structures of g-C3N4, but strongly enlarged the surface area and total pore volume of OMC/g-C3N4 composites. The photodegradation of rhodamine B (RhB) and 2,4-dichlorophenol (2,4-DCP) under visible light irradiation was tested. The photocatalytic efficiencies of the 0.04-OMC/g-C3N4 composite over RhB and 2,4-DCP were about 2.41 times and 3.68 times as high as those of g-C3N4, respectively. It is deduced that the enhanced photocatalytic activity should be attributed to the larger specific surface area and favorable optical property.

Fast and facile preparation of metal-doped g-C3N4 composites for catalytic synthesis of dimethyl carbonate

Zn-doped g-C3N4 materials (Zn-g-C3N4) were prepared by a simple mixing and calcination, using dicyandiamide as a precursor and zinc halide as a dopant. The characterization results of CO2 temperature-programmed desorption and elemental analysis revealed that the introduction of Zn species enhanced the overall basic quantity of g-C3N4. In the transesterification of ethylene carbonate with CH3OH to dimethyl carbonate (DMC), the Zn-g-C3N4 catalysts showed superior catalytic activity to the pure g-C3N4, and the highest DMC yield reached 83.3%, along with stable catalytic reusability and reproducibility. Furthermore, other transition-metal halides (including FeCl3, CuCl2, NiCl2, etc.) could be utilized as dopants for g-C3N4, and the obtained doped g-C3N4 materials also showed high EC conversions above 70%. The upgradation of basic quantity of g-C3N4 was attributed to the reaction between metal halide and the active amine species of g-C3N4. Despite their low surface areas, under the same catalytic conditions, Zn-g-C3N4 catalysts demonstrated remarkably higher catalytic activity than other mesoporous carbon nitride materials.

Fabrication of α-Fe2O3/g-C3N4 composites for cataluminescence sensing of H2S

α-Fe2O3/g-C3N4 composites catalysts were prepared through a facile method of refluxing. Thermogravimetric analysis (TG), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were employed to characterize the as prepared α-Fe2O3/g-C3N4, which displayed distinguished cataluminescence (CTL) properties in the process of detecting H2S gas. When the α-Fe2O3 content in the composite reaches 5.97%, the most outstanding CTL responses are observed. Under the optimized conditions, the linear detection range of the H2S gas sensor was 0.88–7.01μgmL−1 (r=0.998) with the detection limit of 0.5μgmL−1 (S/N=3). Furthermore, the H2S gas sensor showed superior selectivity to H2S gas compared with other fourteen kinds of common volatile organic compounds (VOCs), as well as fast response (0.1s) and recovery (0.6s). These properties render α-Fe2O3/g-C3N4 composite promising candidate for applications in various fields.

Synthesis of g-C3N4 with heating acetic acid treated melamine and its photocatalytic activity for hydrogen evolution

The g-C3N4 is synthesized by directly heating the acetic acid treatment melamine. A combination of XRD, SEM, TEM, PL and UV–vis are utilized to characterize the composition, morphology and optical properties of g-C3N4. This method synthesized g-C3N4 shows smaller particles and some holes which high up the photocatalytic activity compared with the bulk g-C3N4.

High-yield synthesis and optical properties of g-C3N4.

Graphitic carbon nitride (g-C3N4), a metal-free semiconductor with a band gap of 2.7 eV, has received considerable attention owing to its fascinating photocatalytic performances under visible-light. g-C3N4 exhibits high thermal and chemical stability and non-toxicity such that it has been considered as the most promising photocatalyst for environmental improvement and energy conservation. Hence, it is of great importance to obtain high-quality g-C3N4 and gain a clear understanding of its optical properties. Herein, we report a high-yield synthesis of g-C3N4 products via heating of high vacuum-sealed melamine powder in an ampoule at temperatures between 450 and 650 °C. Using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), the chemical composition and crystallization of the as-produced g-C3N4 are demonstrated. A systematic optical study of g-C3N4 is carried out with several approaches. The optical phonon behavior of g-C3N4 is revealed by infrared and Raman spectroscopy, and the emission properties of g-C3N4 are investigated using photoluminescence (PL) spectroscopy, while the photocatalytic properties are explored by the photodegradation experiment.

Visible light photoactivity enhancement via CuTCPP hybridized g-C3N4 nanocomposite

Cu (II) meso-Tetra (4-carboxyphenyl) porphyrin (CuTCPP) hybridized g-C3N4 (CuTCPP/g-C3N4) composites have been facilely synthesized through the ethanol dispersion method. CuTCPP molecules as a sensitizer could easily assemble on the surface of g-C3N4 nanosheets mainly through π–π stacking interaction. The CuTCPP/g-C3N4 composites show much higher photocatalytic activity for phenol degradation than pure g-C3N4 under visible light irradiation. The optimum photocatatlytic activity of the CuTCPP/g-C3N4 composites with weight ratio of CuTCPP at 0.75% is almost 2.2 times as high as that of pure g-C3N4 under the visible light. The enhancement of the visible light photocatalytic activity comes from the efficient electrons transfer from photoexcited CuTCPP molecules to g-C3N4 sheets and more efficiently visible-light harvesting due to the CuTCPP sensitization. Both the holes and ·O2− are main oxidative species of CuTCPP/g-C3N4 for phenol degradation under visible light irradiation. Finally, the possible charge transfer mechanism of enhanced visible light photocatalytic activity was proposed.

Synthesis of graphene with both high nitrogen content and high surface area by annealing composite of graphene oxide and g-C3N4

In this paper, we propose a facile, catalyst-free thermal annealing approach for synthesis of N-doping graphene (NG) using graphitic carbon nitride (g-C3N4) as the nitrogen source. Graphene with nitrogen content up to 13.9 % (atom %) and Brunauer–Emmett–Teller (BET) surface area of 419.6 m2/g can be achieved via thermal annealing composite of graphene oxide (GO) and g-C3N4. The transmission electron microscopy indicates that the NG synthesized by annealing GO/g-C3N4 composite is compact and stacked with large sheets. The atomic force microscopy reveals that the NG was less than three single graphene layers nanosheets with an apparent thickness of about 1.0 nm. This improved synthesis method for producing high nitrogen content and high BET surface area can be extended to prepare multi-element (such as B and N) doping graphene nanosheets.

Synthesis of carbon-doped g-C3N4 composites with enhanced visible-light photocatalytic activity

Novel visible-light-active carbon-doped graphitic carbon nitride composites (C/g-C3N4) were prepared by hydrothermal treatment of the mixture of g-C3N4 and glucose solution. The products were characterized by X-ray diffraction, transmission electron microscopy (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflection spectroscopy (UV–vis), and photocurrent–time measurement (PT). Compared to g-C3N4, the C/g-C3N4 showed enhanced visible-light absorption, adsorptivity and improved photocurrent response. C/g-C3N4 composites also showed enhanced performance for Methylene Blue (MB) photodegradation. The enhanced activity of the C/g-C3N4 composites is attributed to the synergistic effect between the doped carbon and g-C3N4.

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.