3N4 Nanosheets Research Articles

Interfacial coupled engineering of plasmonic amorphous MoO3-x nanodots/g-C3N4 nanosheets for photocatalytic water splitting and photothermal conversion

Semiconductor-based plasmonic materials have attracted extensive attention for photocatalytic systems. However, their photocatalytic reactions are hindered by limited light-harvesting ability and the transfer rate of photo-generated electrons. Herein, vacancy engineering and phase engineering are rationally integrated to develop amorphous molybdenum oxide (a-MoO3−x) nanodots anchored on g-C3N4 as a highly active photocatalyst. Through high localized surface plasmon resonance (LSPR) effect of a-MoO3−x nanodots and tunable electrical properties induced by the heterostructural interface, the Z-scheme a-MoO3−x/g-C3N4 heterostructure demonstrates broadband absorption and the excited photo-generated electrons. Further theoretical calculations demonstrate that the enhancement of photocatalytic and photothermal performance is mainly attributed to the highly localized Anderson tail states of a-MoO3−x. Consequently, the a-MoO3−x/g-C3N4 heterostructure exhibits a photocurrent density of ∼36.5 μA cm−2, which is about 2.7 and 4.1 times higher than that of pure g-C3N4 nanosheets (∼13.5 μA cm−2) and a-MoO3−x nanodots (∼9 μA cm−2), respectively. The photocatalytic performance enhancement relying on defects and long-range disorder of a-MoO3−x in Z-scheme heterostructure is explored.

Construction of Zn0.2Cd0.8S/g-C3N4 nanosheet array heterojunctions toward enhanced photocatalytic reduction of CO2 in visible light

The efficiency of photocatalytic CO2 reduction is severely limited by slow surface reaction kinetics and poor structural stability. In this study, a three-dimensional Zn0.2Cd0.8S/g-C3N4 (ZnCdS/CN) nanosheet array with type Ⅱ-scheme heterojunction structures was prepared using a mild in situ method. This heterojunction structure exhibited greatly improved carrier separation and specific surface area (45 m2 g−1), excellent stability, and broad-spectrum visible-light sensitivity. Without the use of any sacrificial agent, ZnCdS/CN20% demonstrated the highest photocatalytic efficiency of all the samples, with a CH3OH yield of 700.5 μmol·g−1·h−1. The type-Ⅱ-scheme heterojunction structure was responsible for the remarkable activity and stability because the photogenerated holes were transmitted to g-C3N4 across the heterojunction interface for the oxidation reaction, while the photogenerated electrons accumulated on Zn0.2Cd0.8S for the reduction reaction. This structure prevented oxidative corrosion on Zn0.2Cd0.8S and significantly improved the photogenerated electron–hole separation. This synthetic strategy provides new perspectives on the design and construction of efficient heterojunction photocatalysts for the solar-driven catalytic conversion of CO2.

Constructing 0D/1D/2D Z-scheme heterojunctions of Ag nanodots/SiC nanofibers/g-C3N4 nanosheets for efficient photocatalytic water splitting

Efficiently constructing nanostructured Z-scheme heterojunctions with good interface contact is a desired route to optimize the photocatalytic property of the materials. In this work, novel 0D/1D/2D Z-scheme silver/silicon carbide/graphitic carbon nitride (Ag/SiC/CN) photocatalysts were prepared from Ag nanodots loaded on SiC nanofibers/CN nanosheets (SiC/CN) composite, using the calcination and chemical reduction routes. The Ag/SiC/CN composite with an optimal 3% Ag loading dose performs the best H2 evolution rate of 2971 μmol g−1 h−1, which is approximately 8.8, 1.5 and 4.5 times compared to CN, SiC/CN and 3% Ag/CN, respectively. Besides the Ag/SiC/CN composite presents a high apparent quantum efficiency (7.3%) and outstanding photo-corrosion resistance stability. The Ag nanodots are served as efficient carriers transfer center and cocatalyst to construct Z-scheme heterojunction interface, which can help to generate more photo-generated carries, shorten the electron transmission distance and increase the electron transfer rate, certifying that 0D/1D/2D Z-scheme photocatalytic system is high-efficiency and has great advantages in photocatalytic applications.

2D/2D Boron/g-C3N4 Nanosheet Heterojunction Boosts Photocatalytic Hydrogen Evolution Performance

Photocatalysis clean hydrogen production is a modern technology for simultaneously addressing and solving energy and environmental issues, of which the most critical part is to develop a highly efficient photocatalyst. In this work, we rationally designed and synthesized a metal-free 2D/2D boron/g-C3N4 nanosheet heterojunction (B-CN) through an electrostatic self-assembly thermal induction combined with ultrasound-assisted technology. The optimized photocatalyst 3.0B-CN possesses a hydrogen generation rate 35 times that of g-C3N4, which provided an impressive H2 evolution photocatalytic activity. The tight heterojunction architecture via the coupling of two-dimensional boron nanosheets and g-C3N4 nanosheets realizes the enhanced visible light absorption, the increasing carrier concentration, and the rapid transfer of interfacial charge and thus hinders the electron–hole recombination. The coupling of two 2D metal-free nanosheet materials for constructing a 2D/2D layered heterojunction in our work offers pioneering tactics for the design and synthesis of green nonmetal 2D photocatalytic HER materials in the future.

Visible-light induced electron-transfer in MoO3 QDs/g-C3N4 nanosheets for efficient photocatalytic reduction of U(VI)

Visible light-driven photocatalytic technology has become an effective method to remove U(VI) from wastewater. Herein, MoO3 quantum dots (MQDs) were prepared by a one-step oxidation method using molybdenum disulfide as the precursor. The MQDs were used to modify g-C3N4 nanosheet photocatalysts (MQDn-C3N4, where n represents the mass percentage of MQDs) to enhance the photocatalytic performance of g-C3N4 nanosheets. The morphology, chemical composition and optical properties of the MQDn-C3N4 composites were investigated by a series of characterization methods. The MQD3-C3N4 could remove 96.4% of U(VI) after 150 min of illumination, which was about 1.9 times that of g-C3N4. The MQD3-C3N4 samples had excellent stability and recyclability after five cycles. The possible mechanism of the photocatalytic process was proposed through radical trapping experiments and electron spin-resonance, in which the reduction of U(VI) is facilitated by photogenerated e– and •O2– radicals. The MQDn-C3N4 photocatalyst is expected to provide new concepts for the treatment of wastewater containing radionuclides.

Facile synthesis of TiO2/g-C3N4 nanosheet heterojunctions for efficient photocatalytic degradation of tartrazine under simulated sunlight

In this study, TiO2/g-C3N4 nanosheet heterojunctions were successfully fabricated via a facile hydrothermal process and demonstrated to be effective catalyst for tartrazine (TTZ) degradation. The synthesized catalyst was characterized by several analytical methods, including TEM, XRD, UV-DRS, BET, FT-IR, PL, XPS and a series of electrochemical characterizations. The photodegradation of tartrazine (TTZ) under simulated sunlight by TiO2/g-C3N4 is reported for the first time. The TiO2/g-C3N4 composites displayed more excellent photocatalytic performance than pure g-C3N4 and TiO2. The effect of initial TTZ concentration, catalyst dosage, pH and impurity ions on the degradation efficiency were systematically investigated. Under the optimal experimental conditions, the degradation rate still remained about 93% even after 4 cycles, confirming the relatively stable activity of TiO2/g-C3N4. Besides, the free radical scavenging experiments demonstrated that superoxide radical (•O2−) and photogenerated holes (h+) were indispensable active substances for the TTZ degradation. Meanwhile, ultraviolet–visible spectroscopy analysis evidenced that the azo bond (NN) in the TTZ molecule was destroyed during the photocatalytic reaction. Finally, the reaction mechanism and specific steps of TTZ degradation have been inferred in detail. This study provided a valuable reference for the application of composite heterojunction materials in the degradation of pollutants under solar light.

Construction of interface electric field by electrostatic self-assembly: enhancing the photocatalytic performance of 2D/2D Bi12O17Cl2/g-C3N4 nanosheets

Construction of interface electric field by electrostatic self-assembly: enhancing the photocatalytic performance of 2D/2D Bi12O17Cl2/g-C3N4 nanosheets

Solar energy-driven upcycling of plastic waste on direct Z-scheme heterostructure of V-substituted phosphomolybdic acid/g-C3N4 nanosheets

The increasingly massive consumption of plastics is becoming a global pollution disaster, with serious environmental and economic problems. Here we report an efficient and sustainable strategy for the visible-light-driven upcycling of various plastic wastes into high-value-added formic acid. We firstly design and fabricate a self-assembly Z-scheme heterostructure of V-substituted phosphomolybdic acid clusters/g-C3N4 nanosheets (VPOM/CNNS). The Z-scheme charge transfer process is unambiguously elucidated by transient absorption spectra and electron spin resonance studies, which endow VPOM/CNNS heterostructure with efficient charge separation and strong redox potentials. Consequently, VPOM/CNNS heterostructure displays a superior photocatalytic performance toward upcycling of various plastics. The optimal VPOM/CNNS composite exhibits a remarkable formic acid production rate of 24.66 μmol h−1 g−1 for upcycling of polyethylene, which is 262-fold higher than that of pristine CNNS. This work highlights the potential of Z-scheme heterojunction as an unusual tool for the photo-driven upcycling of plastic waste.

HNb3O8/g-C3N4 nanosheet composite membranes with two-dimensional heterostructured nanochannels achieve enhanced water permeance and photocatalytic activity

A photocatalytic membrane for water treatment is required to have an efficient photocatalytic functions and high membrane performances, therefore, it is necessary to design a functional membrane structure that achieves both requirements. Herein, we describe two-dimensional material engineering on heterostructured nanochannels comprising graphitic carbon nitride (g-C3N4) and HNb3O8 nanosheets and demonstrate their potential water treatment applications based on their enhanced water permeance and photocatalytic degradation of organic compounds. Laminar HNb3O8/g-C3N4 composite membranes were fabricated by vacuum filtration. The incorporation of g-C3N4 into the HNb3O8 membrane led to an eight-fold improvement in the membrane’s water permeance relative to that of the laminar HNb3O8 membrane, while maintaining high dye rejection performance. In addition, the HNb3O8/g-C3N4 composite membranes exhibited enhanced photocatalytic degradation of the cationic dye, rhodamine B, because of the formation of a heterojunction between g-C3N4 and HNb3O8 nanosheets with a suitable band-gap alignment. Furthermore, the permeance of an HNb3O8/g-C3N4 composite membrane could be completely restored via light irradiation after BSA fouling. Each type of nanosheet plays an important role as a membrane or photocatalyst component, thereby generating a synergistic effect based on the formation of two-dimensional heterostructured nanochannels in the photocatalytic nanosheet membrane.

A novel cathodic electrochemiluminescent sensor based on CuS/carbon quantum dots/g-C3N4 nanosheets and boron nitride quantum dots for the sensitive detection of organophosphate pesticide

In this project, a novel promising electrochemiluminescence probe based on ternary nanocomposite as CuS/CQDs/g-C3N4NS was demonstrated for the accurate monitoring of diazinon as a popular organophosphate pesticide. This nanocomposite as a promoted luminophore was synthesized by a simple microwave method. Carbon quantum dots and copper sulfide nanostructures displayed a good cooperative effect on the signal improvement. Also, boron nitride quantum dots were introduced as a new and effective co-reactant in the negative potential window for a carbon-based electrochemiluminescence system for the first time. The ultra-sensitive electrochemiluminescence platform was truly used for the analysis of diazinon. The broad linear dynamic range and low limit of detection were obtained from 1.0 × 10−15 to 5.0 × 10−9 M and 2.2 × 10−16 M, respectively. Owing to superior proficiency in accurate diazinon analysis, the developed sensor was used as a new applicable probe for quantitative analysis of diazinon in real samples.

Metal-free Sulfur-doped graphitic carbon nitride-modified GCE-based electrocatalyst for the enhanced electrochemical determination of Omeprazole in Drug formulations and Biological Samples.

This study presents a novel sulfur-doped graphitic carbon nitride (S@g-C3 N4 ) with a wider potential range as electrocatalyst for electrochemical sensor application. The S@g-C3 N4 nanosheets were successfully prepared with a ball milling method by mixing appropriate molar concentration required precursors. The as-synthesized heteroatom-doped graphitic carbon nitride is characterized by spectroscopic techniques including PL, DRS-UV, FT-IR, and Brunauer-Emmett-Teller equation. The morphological features were studied by FE-SEM and HR-TEM analysis. Chit-S@g-C3 N4 -modified glassy carbon electrode (GCE) was employed for the electrochemical detection of omeprazole (OMZ) use in drug formulations. We have noted an oxidation peak current response at a potential of +0.8V versus Ag/AgCl in PBS medium (0.1M, pH 7.0). Differential pulse voltammetry amperometry experimental method can be used to measure the concentration of OMZ for quantitative studies in known samples. Under the optimized experimental condition, the calibration plot was constructed by plotting the peak currents versus OMZ in the linear ranges from 6.0×10-7 to 26×10-5 M. The linear regression equation is estimated to be Ip (μA)=0.9518 (C/μM)+0.3340 with a good correlation coefficient of 0.9996. The lower determination limit was found to be 20nM and the current sensitivity was calculated (31.722μAμM-1 cm-2 ). The developed sensor was utilized successfully to determine the OMZ concentration in drug formulations and biological fluids. These results revealed that the Chit-S@g-C3 N4 -modified GCE showed excellent electroanalytical performance for the detection of OMZ at a low LOD, wider linear range, high sensitivity, good reproducibility, long-term storage stability, and selectivity with an acceptable relative standard deviation value.

Z-scheme MoO3-2D SnS nanosheets heterojunction assisted g-C3N4 composite for enhanced photocatalytic hydrogen evolutions

In this work, the 2D SnS/g-C3N4 nanosheets have been successfully prepared by a facile ultrasonic and microwave heating approach, which formed intimate interfacial contact and suitable energy band structure. The optimized sample displayed enhanced photocatalytic hydrogen evolution from water assisted with Pt co-catalyst, which is much higher than that of pure g-C3N4. After loaded with MoO3 particles, the stability of photocatalysts displayed significate improvement due to the formed Z-scheme heterojunction. With the characterization, the enhanced hydrogen evolution reaction (HER) performance might be ascribed to the improved light-harvesting capability of the composite, lowered charge-transfer resistance, increased electrical conductivity and the co-catalyst effect of SnS. This study provides insights about SnS assisted HER photocatalysts and a new strategy to improve the stability of metal sulfides photocatalysts.

Improved visible-light activities of ultrathin CoPc/g-C3N4 heterojunctions by N-doped graphene modulation for selective benzyl alcohol oxidation

The interface modulation is the key factor affecting the photoactivity of metal phthalocyanine (MPc)/g-C3N4 heterojunctions for aerobic selective alcohol oxidation. Here, we have successfully fabricated the N-doped graphene-modulated CoPc/g-C3N4 nanosheets (CoPc/NG/CN) heterojunctions. Optimal CoPc/NG/CN photocatalyst demonstrates approximately fourfold photoactivity improvement for benzyl alcohol oxidation with ∼99% selectivity toward benzyl aldehyde and of approximately ninefold 2,4-dichlorophenol degradation rate compared with bare CN, using O2 as oxidant. By means of steady-state surface photovoltage responses in N2 atmosphere, time-resolved photoluminescence spectra, single-wavelength photocurrent action spectra, and electrochemical O2 reduction measurements, it is confirmed that the exceptional photoactivities of resulting CoPc/NG/CN heterojunction are attributed to the facilitated interfacial charge transfer between CoPc and CN by the modulation of NG with favorable electron-induced capacity. In addition, more enriched hydroxyl groups of NG by N doping could induce high dispersion of CoPc molecules via H-bonding effect, resulting in the increase of exposed number of CoPc as visible-light absorption units and single Co2+ sites as catalytic centers for O2 activation so as to further benefit the photocatalytic oxidation processes. This work provides a feasible interfacial modulation strategy to fabricate efficient supported MPc-based heterojunction photocatalyst nanomaterials.

A highly efficient (Mo, N) codoped ZnIn2S4/g-C3N4 Z-scheme photocatalyst for the degradation of methylene blue

Fabricating a Z-scheme heterostructure is an effective strategy for the highly efficient photocatalyst. However, the conscious modulation of Z-scheme charge transfer is still a great challenge. Herein, Mo, N (co) doped ZnIn2S4/g-C3N4 nanosheets are successfully synthesized by a sol–gel method. The systematic investigations show that the heterostructure construction and codoping can extend the optical absorption edge and provide more active sites. More importantly, the separation and transfer of photoinduced electron-hole pairs are greatly improved between (Mo, N) codoped ZnIn2S4 and g-C3N4 by the photoelectrochemical and PL spectra results, and forming a Z-scheme charge transfer mechanism in the (Mo, N) codoped ZnIn2S4/g-C3N4. Under the intense synergy among the internal electric field of heterostructure and (Mo, N) codoping, the optimized (0.35% Mo, 2.4 % N) codoped ZnIn2S4/g-C3N4 Z-scheme photocatalyst exhibits an outstanding photocatalytic activity and cyclic stability for methylene blue degradation with the visible light illumination, The degradation rate of (Mo, N) codoped ZnIn2S4/g-C3N4 reaches to 97% after 120 min irradiation, which is 1.3 and 2.6 times higher that of ZnIn2S4/g-C3N4 and ZnIn2S4, respectively. These codoping atoms modulation strategy of Z-scheme charge transfer presents a facile and promising pathway to enhance photocatalytic activity.

Designing S-scheme Au/g-C3N4/BiO1.2I0.6 plasmonic heterojunction for efficient visible-light photocatalysis

A novel S-scheme Au/g-C3N4/BiO1.2I0.6 plasmonic heterojunction was constructed by calcining a mixture of flower-like BiOI and Au/g-C3N4 nanosheets for the first time. This Au/g-C3N4/BiO1.2I0.6 heterojunction exhibited excellent photocatalytic activity in bisphenol AF (BPAF) degradation and Cr(VI) reduction with high cycle stability under visible light irradiation. In particular, the photocatalytic performance of the optimum material developed (4-Au/g-C3N4/BiO1.2I0.6) can reach 0.0174 min−1 (apparent rate of BPAF degradation) and 0.0204 min−1 (apparent rate of Cr(VI) reduction), which were 6.5 and 3.7 times that of pristine g-C3N4, respectively. The high photocatalytic performance was due to the high efficiency of charge separation, the excellent light absorption of localized surface plasmon resonance (LSPR) caused by the Au deposition, and the formation of S-scheme heterojunctions, which maintained strong photocatalytic reduction and oxidation activity. Noticeably, the charge density difference and band offsets of the g-C3N4/BiO1.2I0.6 were calculated. The results revealed that an internal electric field (IEF) was created, which further demonstrated the formation of an S-scheme photocatalytic mechanism.

Enhanced carriers separation in novel in-plane amorphous carbon/g-C3N4 nanosheets for photocatalytic environment remediation

Although carbon-based materials/g-C3N4 heterostructure with an up-down structure in space can inhibit the recombination of charge carriers, the electron transfer is still suppressed by the interlayer van der Waals force. Herein, amorphous carbon is successfully introduced into the g-C3N4 nanosheet (CNS) by a self-conversion process to form an in-plane heterostructure of amorphous carbon/g-C3N4 (CNSC1). Kelvin probe atomic force microscopy (KPFM) and density functional theory (DFT) confirm that g-C3N4 and amorphous carbon are in the same plane, which can generate the surface electric field of CNSC1, providing a driving force for the transfer of electrons from g-C3N4 to amorphous carbon. Meanwhile, the sp2-hybridized π conjugation bond of amorphous carbon can rapidly capture and store photogenerated electrons, inhibiting charge carrier recombination and thus generating more electrons to facilitate the yield of hydroxyl radicals. The photocatalytic activity of CNSC1 for the degradation of tetracycline and rhodamine B is 2.7 times and 4.8 times higher than that of CNS, respectively, due to the efficient interface charge separation. This work is expected to provide a new idea for the combination of carbon materials and g-C3N4.

Visible-Light Induced Electron-Transfer in Moo3 Qds/G-C3n4 Nanosheets for Efficient Photocatalytic Reduction of U(Vi)

Visible-Light Induced Electron-Transfer in Moo3 Qds/G-C3n4 Nanosheets for Efficient Photocatalytic Reduction of U(Vi)

Ultra-thin graphene/g-C3N4 nanosheets with in-plane heterojunction for enhanced visible-light photocatalytic hydrogen evolution performance

ABSTRACT Ultra-thin graphene/g-C3N4 nanosheets (CN/G) with in-plane heterojunction were prepared by facial two-step thermal condensation of urea and glucose under mild conditions to improve photocatalytic hydrogen evolution under visible-light irradiation. The characterisation indicated that graphene was connected to the end of g-C3N4. The thermal exfoliation process can transform the bulk structure of g-C3N4 into ultra-thin nanosheets. Consequently, photocatalytic activity for hydrogen evolution rate of CN/G-0.1 was 704 µmol g–1 h–1, about 14 times higher than that of pure g-C3N4 under visible light irradiation (λ > 420 nm). CN/G-0.1 also exhibited high stability from the cycling tests for 18 h and superior photocatalytic properties at 500 nm. In-plane graphene modification can significantly enhance visible-light absorption and promote photogenerated electron-hole pair separation. On the other hand, ultra-thin nanosheets can increase specific surface area (153.8 m2 g–1) and provide abundant active sites. This study provides a suitable method to prepare g-C3N4 based on highly efficient photocatalysts for metal-free photocatalytic hydrogen evolution.

Nanostructuring Nickel–Zinc–Boron/Graphitic Carbon Nitride as the Positive Electrode and BiVO4-Immobilized Nitrogen-Doped Defective Carbon as the Negative Electrode for Asymmetric Capacitors

Rationally designed compounds with exceptional surface functionalities are greatly necessary for efficient energy-storage technologies. Herein an aqueous battery-type hybrid supercapacitor device is fabricated based on amorphous nickel–zinc–boron/graphitic carbon nitride (Ni–Zn–B/g-C3N4) nanosheet network structures as the cathode and a bismuth vanadate-anchored carbon nanotube matrix with nitrogen dopants and defect sites (BiVO4/NC) as the anode. Interconnected nanosheet-assembled Ni–Zn–B/g-C3N4 porous networks are developed via a scalable liquid-phase reduction method, while the BiVO4/NC nanocomposite frameworks are prepared by a simple chemical precipitation route and annealing treatment. Because of the unique compositional and structural features as well as enhanced electrochemical properties, the as-assembled Ni–Zn–B/g-C3N4//BiVO4/NC aqueous alkaline device with a large working potential of 1.6 V exhibits a remarkable energy-storage capability with a high energy density of 78.4 Wh kg–1 and a power density of 907.7 W kg–1 together with a good cyclic performance (85.3% retention after 8000 cycles). Considering the intriguing results and reasonable design of the cathode and anode materials, this work provides a significant prospect for designing a high-performance energy-storage system. The intrinsically enhanced electrochemical performances of heterostructured Ni–Zn–B/g-C3N4 and BiVO4/NC demonstrate their potential utilization in energy-storage systems.

Multifunctional Ni nanoparticles decorated SiC nanofibers/g-C3N4 nanosheets heterojunctions for drastically increased LED-light-driven hydrogen generation

The development of hydrogen (H2) production photocatalyst with low cost, non-precious metal and high-activity for commercial application is a long-term target and challenge. In this work, novel silicon carbide (SiC) nanofibers/graphitic carbon nitride (g-C3N4) nanosheets (SiC/CNNS) decorated via multipurpose nickel (Ni) nanoparticles were prepared by an easy heat treatment followed byhydrothermalmethod. The tight Ni interface layers as cocatalyst and electron transfer mediator can significantly enhance the H2 production property over SiC/CNNS nanoheterojunctions under light-emitting diode (LED) illumination. The optimal Ni/SiC/CNNS with a massfraction of 10% Ni loading shows the mostsuperior H2-generation rate of 6183 μmol g−1h−1, which is approximately 53, 3 and 227 times compared to CNNS, 10 %Ni/CNNS and SiC/CNNS, respectively. The metallic Ni nanoparticles play the leading and multifunctional roles in improving photocatalyticactivity, includingcollecting the photo-generated electrons efficiently, transferring and separating the charge carriers rapidly, facilitating the H2-production kinetics and decreasing the overpotentials of surface reactions for H2-production. It is highly expected that the multipurpose and non-preciousmetal cocatalyst to form tight interface layers can supply a simple and universal strategy to design high-efficiency cocatalyst-semiconductor–semiconductor photocatalysts for H2 production.