Bulk Graphitic Carbon Nitride Research Articles

Graphitic carbon nitride nanosheet supported silica nanochannel film for enhanced electrochemiluminescence sensing of 2,4,6-trichlorophenol and prochloraz.

The development of simple, rapid, and sensitive methods for detecting pesticide in environmental and food samples holds significant importance. Electrochemiluminescence (ECL) sensing platforms with high resistance to interference and contamination, and reduced consumption of ECL emitters, are highly desirable for such applications. In this work, we present an ECL sensing platform based on a graphitic carbon nitride nanosheets (CNNS) supported vertically ordered mesoporous silica film (VMSF) modified glassy carbon electrode (GCE) for the highly sensitive detection of the environmental pollutant 2,4,6-trichlorophenol (TCP) and the broad-spectrum insecticide prochloraz. Two-dimensional (2D) CNNS were synthesized by exfoliating bulk graphitic carbon nitride (g-C3N4) using concentrated sulfuric acid, serving as a novel conductive and adhesive layer for the growth of a stable VMSF on GCE via an electrochemical assistance self-assembly (EASA) method to prepare VMSF/CNNS/GCE. The electrostatic enrichment capability of VMSF nanochannels for the positively charged ECL emitter tris(2,2'-bipyridyl)ruthenium(ii) (Ru(bpy)3 2+) realized stable and significantly enhanced ECL signals at a low concentration of Ru(bpy)3 2+ (10 μM). Based on the quenching effect of TCP on the ECL signal of Ru(bpy)3 2+, highly sensitive ECL detection of TCP was achieved by the VMSF/CNNS/GCE with a linear range from 10 nM to 0.7 mM and a low detection limit (DL) of 2.2 nM. As the metabolic end product of prochloraz is TCP, indirect ECL detection of prochloraz was also accomplished by measuring the produced TCP. Combined with anti-fouling and anti-interference abilities, as well as signal amplification of VMSF, the developed VMSF/CNNS/GCE sensor enabled the sensitive ECL detection of TCP in pond water and prochloraz in orange peel extract.

Chlorine-Modified Soluble Melem-Based Graphitic Carbon Nitrite: Facile Synthesis, Catalytic Property and Ultrafast 2D IR Spectroscopic Characterization.

On the basis of thermal etching bulk graphitic carbon nitride (g-C3N4), a mild hydrochloric acid treatment method was used in this work to produce g-C3N4 nano-sheets (CNNS) and further carbon nitride with chloride-modification (CNCl). The latter has thinner layer and smaller particle size and exhibit greatly improved dispersibility and solubility in water, DMSO and other polar solvents. A typical photocatalytic reaction in solution driven by CNCl shows a significantly improved photocatalytic performance over bulk g-C3N4 and CNNS. Steady-state analytical tools including SEM, mass, UV-Vis and IR spectroscopies, and time-resolved two-dimensional infrared (2D IR) vibrational spectroscopy, were used together in this work. Better solubility, more flexible structure, smaller size, easier generation of free radicals and lower recombination rate of electron-hole pair, are believed to be reasons for the superior photocatalytic performance of CNCl.

Synergistic effect of light in piezocatalytic activation of peroxymonosulfate using graphtic carbon nitride nanosheets for degradation of organic pollutants

The objective of the study was to understand the photo-piezocatalytic response of graphitic carbon nitride nanosheets (CNNS) for the activation of peroxymonosulfate (PMS). Methylene blue (MB) dye was targeted by PMS activation using CNNS under ultrasonic-assisted piezocatalysis and photo-piezocatalysis in a batch reactor for 120 min. CNNS has shown 98.4% MB removal within 120 min in a batch study (PMS = 200 mg L-1, CNNS = 1 g L-1, ultrasonicator = 40 kHz, UV-A light = 250 W). CNNS (0.0157 min-1) showed 1.3 times higher photo-piezocatalytic activity compared to bulk graphitic carbon nitride (CNB) for PMS activation due to improvement in in-plane polarization. In the photo-piezocatalytic CNNS/PMS/MB system, a scavenging study revealed that the primary contributors for MB removal were hydroxyl radical (.OH) and sulfate radical (SO4.-). The piezoelectric effect combined with light at CNNS improved the excitation of charge carriers, followed by charge carrier separation due to band tilting. Finally, the effects of CNNS dose, PMS dose, and competitive anions were studied for MB removal using CNNS under photo-piezocatalysis. Overall, CNNS is a promising photo-piezocatalyst for the removal of emerging organic pollutants through PMS activation.

Supercritical CH3OH-Triggered Isotype Heterojunction and Groups in g-C3N4 for Enhanced Photocatalytic H2 Evolution.

The structure tuning of bulk graphitic carbon nitride (g-C3N4) is a critical way to promote the charge carriers dynamics for enhancing photocatalytic H2-evolution activity. Exploring feasible post-treatment strategies can lead to effective structure tuning, but it still remains a great challenge. Herein, a supercritical CH3OH (ScMeOH) post-treatment strategy (250-300 °C, 8.1-11.8 MPa) is developed for the structure tuning of bulk g-C3N4. This strategy presented advantages of time-saving (less than 10 min), high yield (over 80%), and scalability due to the enhanced mass transfer and high reactivity of ScMeOH. During the ScMeOH post-treatment process, CH3OH molecules diffused into the interlayers of g-C3N4 and subsequently participated in N-methylation and hydroxylation reactions with the intralayers, resulting in a partial phase transformation from g-C3N4 into carbon nitride with a poly(heptazine imide)-like structure (Q-PHI) as well as abundant methyl and hydroxyl groups. The modified g-C3N4 showed enhanced photocatalytic activity with an H2-evolution rate 7.2 times that of pristine g-C3N4, which was attributed to the synergistic effects of the g-C3N4/Q-PHI isotype heterojunction construction, group modulation, and surface area increase. This work presents a post-treatment strategy for structure tuning of bulk g-C3N4 and serves as a case for the application of supercritical fluid technology in photocatalyst synthesis.

Construction of novel Ru-embedded bulk g-C3N4 photocatalysts toward efficient and sustainable photocatalytic hydrogen production

Novel Ru-embedded bulk graphitic carbon nitride (g-C3N4) photocatalysts containing different wt% of Ru (0.5–2 % wt) were synthesized by a simple mixing method of ruthenium complex with g-C3N4. The photocatalytic activity of the synthesized photocatalysts was assessed for hydrogen production in an aqueous solution containing methanol with and without Pt. The optimal hydrogen production rate of the most active photocatalyst (0.8 % Ru/CN) was 246 μmol/h without Pt and 1021 μmol/h with Pt, which was more than two times higher than pure g-C3N4. Various physiochemical techniques such as X-ray diffraction (XRD), N2 adsorption-desorption isotherms, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), photoluminescence spectroscopy (PL) and transition photocurrent response (PC) were applied to investigate the origin of activity of the Rux/CN photocatalysts. Results indicated that the loading of g-C3N4 with Ru nanoparticles enlarged its surface area and enhanced visible light absorption. Importantly, Ru nanoparticles promoted the charge carrier separation and transfer efficiency of g-C3N4 revealed by the PL and PC measurements, enhancing the photocatalytic activity of the embedded photocatalyst. Furthermore, XPS proved the existence of Ru (II) of RuO2 and metallic Ru0. The Ru-embedded g-C3N4 showed high photocatalytic activity, which makes them attractive materials for further applications in photocatalysis.

Sugars induced exfoliation of porous graphitic carbon nitride for efficient hydrogen evolution in photocatalytic water-splitting reaction

Photocatalytic hydrogen evolution holds great promise for addressing critical energy and environmental challenges, making it an important area in scientific research. One of the most popular photocatalysts is graphitic carbon nitride (gCN), which has emerged as a noteworthy candidate for hydrogen generation through water splitting. However, ongoing research aims to enhance its properties for practical applications. Herein, we introduce a green approach for the fabrication of porous few-layered gCN with surface modifications (such as oxygen doping, carbon deposition, nitrogen defects) with promoted performance in the hydrogen evolution reaction. The fabrication process involves a one-step solvothermal treatment of bulk graphitic carbon nitride (bulk-gCN) in the presence of different sugars (glucose, sucrose, and fructose). Interestingly, the conducted time-dependent process revealed that porous gCN exfoliated in the presence of fructose at 180 °C for 6 h (fructose_6h) exhibits a remarkable 13-fold promotion of photocatalytic hydrogen evolution compared to bulk-gCN. The studied materials were extensively characterized by microscopic and spectroscopic techniques, allowing us to propose a reaction mechanism for hydrogen evolution during water-splitting over fructose_6h. Furthermore, the study highlights the potential of employing a facile and environmentally friendly fructose-assisted solvothermal process to improve the efficiency and stability of catalysts based on graphitic carbon nitride.

A novel method to synthesis of oxygen doped graphitic carbon nitride with outstanding photocatalytic efficiency for the degradation organic pollutants

Contamination of water sources with organic pollutants seriously threatens the environment and living organisms, so it is necessary to remove them from these sources with a proper method. Photocatalytic degradation of such pollutants can be an effective, low-cost and eco-friendly method. In this study, a new method, porous oxygen-doped Graphitic carbon nitride (POCN) photocatalyst was synthesized by pre-exfoliation of bulk graphitic carbon nitride in hydrogen peroxide followed by calcination of the resulting exfoliated and oxygenated sample at 550 °C. In fact, in this method, a combination of three strategies, nanostructure preparation, band gap engineering and defect introduction into the g-C3N4 were used to improve the efficiency of photocatalyst. The synthesized sample was characterized using XRD, FESEM, TEM, FTIR, DRS, PL, EDX, XPS, and BET-EJH. The efficiency of the prepared photocatalyst was evaluated with its ability to degrade Congo Red (CR) in aqueous solution under visible light using two light sources, LED lamp and daylight. POCN removed the CR in a short time. The degradation rate was higher under sunlight. The free radical trapping tests showed that superoxide radical anions (O2−) are the active species and are mainly responsible for color degradation.

Iron integrated carbon nitride: A recoverable heterogeneous catalyst for the construction of bis (hetero/homoarylidene)cycloalkanones

Iron integrated graphitic carbon nitride (GCN) was synthesized by adopting co‐precipitation method. No appreciable change in XRD main peak of both GCN and Fe(III)‐GCN indicates the lattice structure remains the same and there is no bulk doping of Fe(III). More sharp IR bands of Fe(III)‐GCN between 1000 and 1750 cm−1 compared with GCN reflect ordered packing of tri‐s‐triazine units in the nanosheets. Scanning electron microscopy (SEM) analysis reveals less thin and large two dimensional sheets have formed from bulk GCN during catalyst preparation. The absence of bright spots in transmission electron microscopy (TEM) indicates that there is no crystalline metal oxide phase confirming that iron(III) is present as ions. Fe(III)‐GCN was then exploited as an efficient heterogeneous catalyst for the synthesis of bis (hetero/homoarylidene)cycloalkanones from heteroaromatic/homoaromatic carbaldehydes and cycloalkanone through carbon–carbon double bond construction. The reaction effected well in water, a green solvent as a reaction medium at ambient temperature. The catalytic competency exposed good performance towards reusability. Added advantages include easy preparation and inexpensiveness.

Dimensionality effects of g-C3N4 from wettability to solar light assisted self-cleaning and electrocatalytic oxygen evolution reaction

Unique interfacial properties of 2D materials make them more functional than their bulk counterparts in a catalytic application. In the present study, bulk and 2D graphitic carbon nitride nanosheet (bulk g-C3N4 and 2D-g-C3N4 NS) coated cotton fabrics and nickel foam electrode interfaces have been applied for solar light-driven self-cleaning of methyl orange (MO) dye and electrocatalytic oxygen evolution reaction (OER), respectively. Compared to bulk, 2D-g-C3N4 coated interfaces show higher surface roughness (1.094 > 0.803) and enhanced hydrophilicity (θ ∼ 32° < 62° for cotton fabric and θ ∼ 25° < 54° for Ni foam substrate) due to oxygen defect induction as confirmed from morphological (HR-TEM and AFM) and interfacial (XPS) characterizations. The self-remediation efficiencies for blank and bulk/2D-g-C3N4 coated cotton fabrics are estimated through colorimetric absorbance and average intensity changes. The self-cleaning efficiency for 2D-g-C3N4 NS coated cotton fabric is 87%, whereas the blank and bulk-coated fabric show 31% and 52% efficiency. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis determines the reaction intermediates for MO cleaning. 2D-g-C3N4 shows lower overpotential (108 mV) and onset potential (1.30 V) vs. RHE for 10 mA cm−2 OER current density in 0.1 M KOH. Also, the decreased charge transfer resistance (RCT = 12 Ω) and lower Tafel's slope (24 mV dec−1) of 2D-g-C3N4 make it the most efficient OER catalyst over bulk-g-C3N4 and state-of-the-art material RuO2. The pseudocapacitance behavior of OER governs the kinetics of electrode-electrolyte interaction through the electrical double layer (EDL) mechanism. The 2D electrocatalyst demonstrates long-term stability (retention ∼94%) and efficacy compared to commercial electrocatalysts.

Photocatalytic Degradation of Diclofenac by Nitrogen-Doped Carbon Quantum Dot-Graphitic Carbon Nitride (CNQD)

In this study nitrogen-doped carbon quantum dots/graphitic carbon nitride nanosheet (CNQD) composites with different contents of nitrogen-doped carbon quantum dots (NCQDs; 2, 4, 6, and 8 wt%) were synthesized. The morphological, physicochemical, and photoelectrochemical properties were investigated using complementary methods such as scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectroscopy in diffuse reflectance (DRS), photoluminescence (PL), nitrogen physisorption (BET), photocurrent response, and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the synthesized materials was assessed during diclofenac (DCF) degradation in an aqueous solution under visible light irradiation. As a result, improved photocatalytic efficiency in DCF degradation was observed for all the CNQD composites compared with bulk graphitic carbon nitride (bCN) and nanosheet g-C3N4 (CNS). The fastest DCF degradation was observed for the 6 wt% NCQD on the surface of CNS (CNQD-6), which removed 62% of DCF in 3 h, with an associated k value of 5.41 × 10−3 min−1. The performance test results confirmed the contribution of NCQDs to enhancing photocatalytic activity, leading to an improvement factor of 1.24 over bCN. The morphology of the CNS and the synergistic interaction between NCQDs and CNS were essential elements for enhancing photocatalytic activity. The photoelectrochemical data and photoluminescence analyses showed the efficient migration of photoexcited electrons from NCQDs to the CNS. The reduced charge recombination rates in CNQD photocatalysts might be due to the synergistic interaction between NCQDs and CNS and the unique up-conversion photoluminescence properties of NCQDs. Further investigations revealed that the photogenerated superoxide radicals (•O2−) predominated in the degradation of DCF, and this photocatalyst had good reusability and toxicity reduction abilities. This work provides insight into the effects of NCQDs on the CNS surface to enhance its potential to remove emerging organic pollutants from water and wastewater.

Cyano-2-oxopyridines: Green synthesis, cytotoxicity evaluation and molecular docking study

An efficient four-component and one-pot synthesis of 1,6-diamino-3,5-dicyano-2-oxopyridine compounds were investigated in the presence of three catalysts such as bulk and nanosheet graphitic carbon nitride and IS@SMNPs (piperazinium ionic salt attached on silica-coated magnetic nanoparticle) as recyclable heterogeneous catalysts. From the results, the magnetic nanocatalyst was the best among examined catalysts. The highest yield (85%) and the shortest reaction time (40 min) were obtained (for the four-component reaction between benzaldehyde, malononitrile, ethyl cyanoacetate and hydrazine hydrate) in the presence of 50 mg of‏ ‏IS@SMNPs at room temperature. Recycling of IS@SMNPs was tested, and after the fifth cycle, 80% yield was obtained. Good yields in a short time, simple recycling, and being environmentally friendly are advantages of the magnetic catalyst. MTT assay screened the cytotoxicity of 6a, 6b, 6e, and 6h derivatives against two carcinoma cell lines, such as HeLa and MCF-7 (estrogen receptor-dependent). 6h and 6b exhibited the most potent cytotoxicity, respectively, and 6b showed the lowest one against both cell lines. The interactions of selected derivatives and Genistein (an estrogen receptor inhibitor) in the active site of estrogen receptor-α were predicted using molecular docking. The docking results of synthetic compounds illustrated similar interactions to redocked Genistein in the active site, and compounds 6e and 6h had the highest binding affinity.

UV light-induced oxygen doping in graphitic carbon nitride with suppressed deep trapping for enhancement in CO2 photoreduction activity

• Oxygen (O) element is introduced in the bulk graphitic carbon nitride (CN) for the first time through a precursor pretreatment by ultraviolet (UV) light irradiation. • The doped O non-metal photocatalyst of CN increased visible light absorption and enhanced carrier density. • The optimized sample has lower charge recombination and suppressed electron deep trapping. • The optimized sample shows enhanced photoreduction activity of CO2 to CH4. While photoreduction of CO 2 to CH 4 is an effective means of producing value-added fuels, common photocatalysts have poor activity and low selectivity in photocatalytic CO 2 -reduction processes. Even though creating defects is an effective photocatalyst fabrication route to improve photocatalytic activity, there are some challenges with the facile photocatalyst synthesis method. In this work, an O element is introduced into a graphitic carbon nitride (CN) skeleton through a precursory ultraviolet light irradiation pretreatment to increase the visible light absorption and enhance the carrier density of this modified non-metal CN photocatalyst; the charge transfer dynamics thereof are also studied through electrochemical tests, photoluminescence spectroscopy, and nanosecond transient absorption. We verify that the optimized sample exhibits lower charge recombination and a suppressed 84 ns electron-trapping lifetime, compared to the 103 ns electron-trapping lifetime of the CN counterpart, and thereby contributes to robust detrapping and a fast transfer of active electrons. Through density functional theory calculations, we find that the improved light absorption and increased electron density are ascribed to O-element doping, which enhances the CO 2 adsorption energy and improves the CO 2 -to-CH 4 photoreduction activity; it becomes 17 times higher than that of the bare CN, and the selectivity is 3.8 times higher than that of CN. Moreover, the optimized sample demonstrates excellent cyclic stability in a 24-hour cycle test.

Efficient Photodegradation of Methylene Blue using WLED with Nanosphere Graphitic Carbon Nitride Compared with its Bulk Counterpart

Herein, a simple solvothermal synthesis of graphitic carbon nitride nanosphere (g-CNN) at 180 ºC is reported. The photocatalytic activity of g-CNN was studied under an in-house developed white light emitting diode (WLED) reactor and characterized by FESEM, PXRD, FTIR, EDX, UV-visible spectroscopy and BET isotherm. The g-CNN has absorbance in visible light region and exhibits enhanced photocatalytic activity compared to bulk graphitic carbon nitride (BGCN) for photodegradation of methylene blue, which attributes to its lower surface area. The photocatalytic performance of g-CNN as function of pH of dye solution and catalyst amount were also studied. The g-CNN can be used for three repeated cycles with minimal change in photocatalytic efficiency. The solvothermal synthesis method at relative low temperature introduces terminal oxygen functionalities in g-CNN, which enhance light absorption and accelerate electron transfer results in improvement of photocatalytic efficiency of g-CNN. The results demonstrated the effectiveness of g-CNN as a photocatalyst for the treatment of water using visible light from WLED.

Architecting Ultrathin Graphitic C3N4 Nanosheets Incorporated PVA/Gelatin Bionanocomposite for Potential Biomedical Application: Effect on Drug Delivery, Release Kinetics, and Antibacterial Activity.

Planar (2D) nanomaterials are garnering broad recognition in diverse scientific areas because of their intrinsic features. Herein, bulk graphitic carbon nitride (g-C3N4) was prepared from melamine, which was exfoliated to produce g-C3N4 nanosheets. The prepared g-C3N4 nanosheets were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), photo luminescence (PL) spectroscopy, and dynamic light scattering (DLS). The stable dispersion of a g-C3N4 nanosheet was incorporated into a PVA/Gelatin matrix to explore its efficacy as a promising drug carrier. A remarkable 42% increase in tensile strength for 1% g-C3N4/PVA/Gelatin was attained compared with that of the PVA/Gelatin film. Thermal stability increased due to addition of g-C3N4 nanosheet in the PVA/Gelatin film, where the maximum thermal degradation temperature increased by 9.5 °C when the 1% nanosheet was added to the PVA/Gelatin film. Moreover, the g-C3N4 nanosheets and g-C3N4/PVA/Gelatin showed no cytotoxicity against HeLa and BHK-21 cells. To investigate the in vitro drug releasing efficacy, ciprofloxacin was incorporated into g-C3N4/PVA/Gelatin. Experimental results showed a 62% drug release within 120 min at physiological pH 7.4. The data was curve fitted by different kinetic models of drug release to understand the drug release mechanism. The experimental data was found to fit best with the Higuchi model and revealed the diffusion control mechanism of drug release. Additionally, antibacterial study confirmed the drug release potency from g-C3N4/PVA/Gelatin film on both Gram-positive and Gram-negative bacteria. The above-mentioned promising findings might lead to an opportunity of using g-C3N4 as a potential drug carrier.

Luminescent and Photocatalytic Properties of Bulk and Crystalline Graphitic Carbon Nitride

Luminescent and Photocatalytic Properties of Bulk and Crystalline Graphitic Carbon Nitride

Enhanced photocatalytic organic pollutant degradation and H2 evolution reaction over carbon nitride nanosheets: N defects abundant materials

Post thermal treatment of bulk graphitic carbon nitride (g-C3N4) by ammonia gas acts as a significant structure regulation approach, while pure ammonia-assisted g-C3N4 synthesis from precursors like melamine is rarely investigated. Here we prove the synthesis of N-defects abundant carbon nitride nanosheets (ACN) through a one-pot thermal polymerization of melamine in pure ammonia gas, for photocatalytic organic pollutant removal in water and H2 evolution applications. Compared to bulk g-C3N4 (BCN), ACN-550 (ACN prepared at 550 °C) exhibited thin-layered porous morphology with higher surface area and abundant N defects, resulting in wider distribution of active sites. Moreover, the abundant N defects in the heptazine heterocycle structure could change the electronic structure of g-C3N4, leading to more efficient transport of photogenerated charge carriers and enhanced photoreduction potential, which gives rise to notable improvement activities in photocatalytic reaction. With superoxide ion radical and photoinduced holes as the predominant reactive species, ACN-550 realized efficient photocatalytic bisphenol A (BPA) degradation, which is 1.6- and 4.7-fold high over commercial TiO2 (P25) and BCN, respectively. ACN-550 exhibited excellent reusability and stability in five consecutive photocatalytic BPA degradation tests. In photo-reductive H2 production system by ACN-550, 761.8 ± 4.3 μmol/h/g H2 was produced, which was 11.6-fold as high as that by BCN.

Synthesis of Highly Active Doped Graphitic Carbon Nitride using Acid‐Functionalized Precursors for Efficient Adsorption and Photodegradation of Endocrine‐Disrupting Compounds

AbstractA highly active non‐metallic doped bulk graphitic carbon nitride (g‐C3N4) was synthesized via acid‐functionalized melamine decomposition. Specifically, melamine was treated with acetic acid, sulfuric acid, and phosphoric acid to obtain oxygen, sulfur, and phosphorus‐doped g‐C3N4 derivatives. Sulfur‐doped g‐C3N4 exhibited remarkable photocatalytic activity to degrade two environmentally harmful hormones, 17β‐estradiol, and 17α‐ethinylestradiol, due to its narrow energy bandgap and high surface area. The hormones were removed entirely in 30–45 min by adsorption in the dark, followed by photodegradation under visible light (430 nm). Furthermore, the pseudo‐second‐order kinetic model fitted the adsorption kinetics well, and photocatalytic degradation followed the exponential decay model. LC–MS identified the intermediate products for the photodegradation of 17β‐estradiol (E2). This study provides a simple one‐step method to synthesize highly reactive metal‐free doped bulk g‐C3N4 photocatalysts to remove harmful water pollutants.

Efficient charge transfer in Co-doped CeO2/graphitic carbon nitride with N vacancies heterojunction for photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution is a promising and environmentally friendly strategy to prepare renewable energy sources thus addressing the energy crisis and environmental issues, and it is crucial to develop an ideal photocatalytic for highly efficient H2 production. Herein, the Co-doped CeO2 decorated on graphitic carbon nitride with N vacancies (NVs) heterostructure photocatalyst (Co-CeO2/DCN) is prepared via a simple self-assembly method. Due to the extended light absorption range, and efficient charge separation and migration derived from the introduction of NVs and the heterojunction structure, the photocatalytic activity of the Co-CeO2/DCN is largely promoted. The optimal sample 20-Co-CeO2/DCN shows a high H2 evolution rate of 1077.02 μmol g−1h−1 (λ > 400 nm), which is 113 and 33 times higher than the bare bulk graphitic carbon nitride (BCN) and CeO2, respectively. This work will provide a new strategy to develop high-performance photocatalysts using defect engineering and heterojunction engineering for H2 evolution.

Graphitic carbon nitride/few-layer graphene heterostructures for enhanced visible-LED photocatalytic hydrogen generation

Few-layer graphene (FLG, 2–7 nm thickness) prepared by catalytic chemical vapour deposition (c-CVD), and bulk graphitic carbon nitride (g-C3N4; GCN) were assembled to develop novel 2D/2D xFLGy/GCN heterostructures. The impact of FLG loading and morphology on the activity of GCN has been evaluated towards H2 generation from water splitting under visible-LED irradiation. The heterostructures, characterised by UV–vis DRS, photoluminescence, EPR, Raman, AFM, XRD, XPS, SEM/TEM/STEM and photocurrent, present strong interfacial interaction and show higher photocatalytic activity than pure GCN. The best performing material, 2FLG10/GCN, generated 1274 g−1 h−1 of H2, i.e., 4-times higher than pure GCN. The improved photoactivity was ascribed to a synergistic effect between GCN and FLG, owing to: i) efficient charge separation of photoinduced electron-hole pairs through electron transfer from GCN to FLG, ii) increased surface area, and iii) enhanced visible light absorption. Moreover, the best performing composite presents high stability after four successive cycles with no significant change in its activity.

One-Dimensional P-Doped Graphitic Carbon Nitride Tube: Facile Synthesis, Effect of Doping Concentration, and Enhanced Mechanism for Photocatalytic Hydrogen Evolution.

P-doped graphitic carbon nitride tubes (P-CNTS) with different P concentrations were successfully fabricated via a pre-hydrothermal in combination with a calcination process under a nitrogen atmosphere. The as-prepared samples exhibited excellent photocatalytic performance with a hydrogen production rate (HPR) of 2749.3 μmol g−1 h−1, which was 17.5 and 6.6 times higher than that of the bulk graphitic carbon nitride (CNB) and graphitic carbon nitride tube (CNT). The structural and textural properties of the P-CNT samples were well-investigated via a series of characterization methods. Compared with the bulk g-C3N4, the tubular structure of the doped samples was provided with a larger specific surface area (SSA) and a relatively rough interior. Besides the above, surface defects were formed due to the doping, which could act as more active sites for the hydrogen production reaction. In addition, the introduction of the P element could effectively adjust the band-gap, strengthen the harvest of visible-light, and boost the effective separation of photogenerated charges. More interestingly, these findings can open up a novel prospect for the enhancement of the photocatalytic performance of the modified g-C3N4.