Graphene-like Structure Research Articles

Contorted hexabenzocoronene derivatives as a universal organic precursor for dimension-customized carbonization

This paper introduces contorted hexabenzocoronene (c-HBC) derivatives as a potential universal precursor for use in synthesis of sp 2 -crystalline carbon materials that have dimensionalities ranging from 1-D to 3-D. Carbon products with different dimensions and high crystallinity were synthesized by controlling the assembly dimensions and intermolecular interactions of c-HBC derivatives, which are largely affected by the edge element and the deposition conditions. Further control of crystallinity was achieved by involving copper vapor; the effect is shown to be limited by the thickness of the assembled c-HBC layer. Study of the carbonization of c-HBC allowed development of an effective strategy to grow graphene-like structure on arbitrary substrates. This ability is expected to be a foundation for designed synthesis of graphitic carbons that have optimum morphology and dimensions for targeted applications.

Preparation of Carbon Dots with Ultrahigh Fluorescence Quantum Yield Based on PET Waste.

Environmentally friendly polyethylene terephthalate-based carbon dots (PET-CDs) with ultrahigh fluorescence quantum yield were prepared with waste PET textiles as raw materials. First, oligomers were prepared from the reaction of waste PET textile and ethylene glycol by the microwave method. Then, the mixture without isolation and purification as well as pyromellitic acid and urea were adopted as precursors for the preparation of PET-CDs by the hydrothermal method. It was found that the as-prepared PET-CDs had a spherical structure with an average particle size of 2.8 nm. The carbon core of PET-CDs was a graphene-like structure doped with nitrogen atoms in the form of pyrrole nitrogen and the surface contained −NH2, which is convenient for modification and functionalization with various materials in the form of chemical bonds. The as-prepared PET-CDs exhibit excitation-independent emission properties in the range from 340 to 440 nm, and the best excitation and emission wavelengths of PET-CDs are 406 and 485 nm, respectively, while the fluorescence quantum yield is 97.3%. In terms of the application, the as-prepared PET-CDs could be adopted as a fluorescence probe for the detection of Fe3+, and the limit of detection is as low as 0.2 μmol/L. The mechanism of PET-CDs by Fe3+ was found to be the static quenching mechanism. In addition, PET-CDs can be used in LEDs and fluorescent anticounterfeiting.

Engineering the electronic structure of high performance FeCo bimetallic cathode catalysts for microbial fuel cell application in treating wastewater

The development of high-performance, strong-durability and low-cost cathode catalysts toward oxygen reduction reaction (ORR) is of great significance for microbial fuel cells (MFCs). In this study, a series of bimetallic catalysts were synthesized by pyrolyzing a mixture of g-C3N4 and Fe, Co-tannic complex with various Fe/Co atomic ratios. The initial Fe/Co atomic ratio (3.5:0.5, 3:1, 2:2, 1:3) could regulate the electronic state, which effectively promoted the intrinsic electrocatalytic ORR activity. The alloy metal particles and metal-Nx sites presented on the catalyst surface. In addition, N-doped carbon interconnected network consisting of graphene-like and bamboo-like carbon nanotube structure derived from g-C3N4 provided more accessible active sites. The resultant Fe3Co1 catalyst calcined at 700 °C (Fe3Co1-700) exhibited high catalytic performance in neutral electrolyte with a half-wave potential of 0.661 V, exceeding that of the commercial Pt/C (0.6 V). As expected, the single chamber microbial fuel cell (SCMFC) with 1 mg/cm2 loading of Fe3Co1-700 catalyst as the cathode catalyst afforded a maximum power density of 1425 mW/m2, which was 10.5% higher than commercial Pt/C catalyst with the same loading (1290 mW/m2) and comparable to the Pt/C catalyst with 2.5 times higher loading ( 1430 mW/m2). Additionally, the Fe3Co1-700 also displayed better long-term stability over 1100 h than the Pt/C. This work provides an effective strategy for regulating the surface electronic state in the bimetallic electro-catalyst.

Biomass-Derived Mesoporous Nanoarchitectonics with Magnetic MoS2 and Activated Carbon for Enhanced Adsorption of Industrial Cationic Dye and Tetracycline Contaminants

Discharging industrial wastewater containing dyes and antibiotics will irreversibly damage the overall environment and human health and prosperity. In this study, magnetic Fe3O4 and MoS2 were loaded on biomass activated carbon (BAC) using co-precipitation and hydrothermal methods, respectively, to obtain MoS2 functionalized magnetic biomass activated carbon (MoS2-mBAC), which was used to remove tetracycline hydrochloride (TC) and crystal violet (CV) in wastewater. A series of characterization methods such as SEM, TEM, FT-IR, XRD, VSM and BET were used. The results showed that MoS2-mBAC has abundant oxygen-containing functional groups, high magnetic properties, large specific surface area (984.05[Formula: see text]cm2/g), and MoS2 nanoflowers with a graphene-like structure. Moreover, the whole adsorption process was endothermic, which can be well fitted by pseudo-second-order kinetic and Langmuir model. The maximum adsorption capacity for TC and CV at the optimum pH reached 286.53[Formula: see text]mg/g and 568.18[Formula: see text]mg/g. Compared to BAC and mBAC, the adsorption performance of MoS2-mBAC was greatly improved. After five cycles, the removal rate was still high. MoS2-mBAC has broad application prospects in wastewater treatment due to its unique advantages, such as wide source, simple process, good performance and high economical availability.

Soft-template-assisted synthesis of Petals-like MoS2 nanosheets covered with N-doped carbon for long cycle-life sodium-ion battery anode

The Petals-like N -doped carbon@MoS 2 (N–C@MoS 2 ) nanosheets are elaborately constructed by g-C 3 N 4 soft-template. As a remarkable anode for SIBs, the N–C@MoS 2 electrode has long-term stability properties, which delivers high capacities of 246 mA h/g at 1.5 A/g after 1000 cycles. • G-C 3 N 4 template inhibits the agglomeration of MoS 2 and realize nitrogen doping of carbon layer. • N -doped carbon layers can improve electronic conductivity and ionic diffusion rate. • The electrode can deliver the capacity of 246 mA h g −1 at 1.5 A/g after 1000 cycles. • The superior performance is ascribed to enhanced conductivity and alleviation volume variation. Molybdenum disulphide (MoS 2 ) is a promising anode material for sodium-ion batteries (SIBs) owing to its graphene-like layered structure and high-capacity (670 mAh/g). However, its inherent poor electrical conductivity and slow Na-ion transportation are the two vital factors limiting its application in SIBs. Herein, the petals-like N -doped carbon@MoS 2 (N–C@MoS 2 ) nanosheets anode are elaborately constructed by the MoS 2 host, g-C 3 N 4 soft-template and carbonated pyrrole conductive matrix. Particularly, the g-C 3 N 4 as a soft-template can effectively inhibit the agglomeration of MoS 2 nanosheets during high temperature treatment and realize nitrogen doped of carbon layer. Most importantly, N -doped carbon layers can improve the electronic ionic diffusion rate and conductivity as well as generate numerous active sites. The volume expansion of MoS 2 is also mitigated due to the constraint of carbon layer by improving the surface electrical property and surface activity. Therefore, the N–C@MoS 2 electrode displays excellent long cycle-life and high-capacity as SIBs anode, which delivers high-capacity of 399 and 246 mAh/g after 300 and 1000 cycles at 0.2 and 1.5 A/g, respectively. The idea of preparing N–C@MoS 2 composite material based on g-C 3 N 4 soft-template afford experimental origin for the further progress of Na-storage device and can be certainly stretched to other transition metal compounds that can form composite structure with g-C 3 N 4 .

Controllable and Gradient Wettability of Bilayer Two-Dimensional Materials Regulated by Interlayer Distance.

Surfaces with controllable and gradient wettability often require an elaborate design of the microstructure or its response under electrical, thermal, optical, pH, and other stimuli. Generally, the wettability change under these physical or chemical effects relies on a complex mechanism that is difficult to be quantitatively described. In this study, an online controlling strategy for surface wettability and the corresponding theoretical model are put forward based on a bilayer graphene-like atomic structure. Molecular dynamics results indicate that the surface wettability varies toward hydrophilicity after sticking a bottom material regardless of its wettability. But such an influence becomes weak with increasing interlayer distance, and the overall wettability approaches that of the upper layer material gradually. This variation is elucidated by the increase of the work of adhesion, providing new insight into the wetting transparency of graphene. A theoretical model of the governing relationship is established based on the work of adhesion, which correlates the overall surface wettability with the interlayer distance and the wettabilities of individual materials. Moreover, a surface with a uniform wettability gradient is achieved by inclining the bottom material. The spontaneous and steady motion of droplets can be induced by this gradient wettability. The relevant speedup behavior is evaluated through a theoretical model considering the varying interlayer distance, which reveals the critical role of the lower layer. This study proposes a novel strategy for controllable wetting and relevant gradient surfaces using prevailing two-dimensional materials, paving new routes to many applications such as microfluidic chips, virus diagnosis, and intelligent sensors.

Construction of defective MoxW1-xS2/Cu7.2S4 polyhedral heterostructures for fast sodium storage

Molybdenum disulfide (MoS2) has great potential applications for Na+-storage mainly for its high capacity and layered graphene-like structure. However, large volume changes and poor electrochemical kinetics restrict the electrochemical performances of metal chalcogenides. Thus, defective MoxW1-xS2/Cu7.2S4 (MWS/CS) polyhedrons (DPs) composed of heterostructured MWS/CS nanosheets have been synthesized by a liquid chemical technique. The heterointerface formed between MWS and CS is mainly ascribed to its high and stable performance by stabilizing the electrochemical reaction products, promoting the electrons and Na+ ions migration and buffering the volume expansion. Eventually, MWS/CS DPs displays a high reversible capacity (566 mAh/g at 0.2 A/g) with upper initial coulombic efficiency of 96.4 %, good rate capability (459.9, 419.2 and 417.2 mAh/g at 1.0, 5.0, 10.0 A/g, separately) and excellent cycling stability (553.1 mAh/g at 5.0 A/g after 1000 cycles).

Fabricating Graphene Oxide/h-BN Metal Insulator Semiconductor Diodes by Nanosecond Laser Irradiation.

To employ graphene’s rapid conduction in 2D devices, a heterostructure with a broad bandgap dielectric that is free of traps is required. Within this paradigm, h-BN is a good candidate because of its graphene-like structure and ultrawide bandgap. We show how to make such a heterostructure by irradiating alternating layers of a-C and a-BN film with a nanosecond excimer laser, melting and zone-refining constituent layers in the process. With Raman spectroscopy and ToF-SIMS analyses, we demonstrate this localized zone-refining into phase-pure h-BN and rGO films with distinct Raman vibrational modes and SIMS profile flattening after laser irradiation. Furthermore, in comparing laser-irradiated rGO-Si MS and rGO/h-BN/Si MIS diodes, the MIS diodes exhibit an increased turn-on voltage (4.4 V) and low leakage current. The MIS diode I-V characteristics reveal direct tunneling conduction under low bias and Fowler-Nordheim tunneling in the high-voltage regime, turning the MIS diode ON with improved rectification and current flow. This study sheds light on the nonequilibrium approaches to engineering h-BN and graphene heterostructures for ultrathin field effect transistor device development.

High-Performance Monolayer BeN2 Transistors With Ultrahigh On-State Current: A DFT Coupled With NEGF Study

Conventional field-effect transistors (FETs) based on silicon downscaling are approaching physical limits, and thus, it is urgent to explore additional novel solutions to address this issue. The 2-D semiconductors have unique advantages as the channel material and provide a promising prospect for high-performance FETs in the post-Moore era. In this work, a new 2-D semiconductor, monolayer BeN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , is studied for the FET performance limits through first-principle quantum-transport simulations. Monolayer BeN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> exhibits a graphene-like planar structure with a direct bandgap of 1.3 eV. Transfer characteristics of sub-10-nm BeN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> FETs are thoroughly assessed through scaling gate length. In particular, 2-D BeN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> FETs with 10-nm gate present the ultrahigh ON-state current above <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4500\,\, \mu \text{A}/\mu \text{m}$ </tex-math></inline-formula> for high-performance applications. Also, we realize the significant reduction of gate length (only 2.5 nm) against the International Technology Roadmap for Semiconductors (ITRS) requirements through introducing underlap structures. In addition, the performance of single devices based on monolayer BeN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is evaluated and compared with some of the recently proposed 2-D devices.

Optical Properties of 1D ZnO/MoS\(_2\) Heterostructures Synthesized by Thermal Evaporation Method

MoS2 material attracts a great attention from researchers due to its graphene-like structure and the bandgap difference between its hexagonal monolayer and bulks. Recently, ZnO/MoS2 heterostructures have been received significant interest due to their distinguished properties. In this study, one-dimensional ZnO and ZnO/MoS2 heterostructures were successfully synthesized by a thermal co-evaporation method. Compare with ZnO, the band-to-band emission of ZnO/MoS2 heterostructures establishes a “blueshift” towards a shorter wavelength. It could be explained by the lattice strain in ZnO/MoS2 heterostructures due to the difference of primitive cell of ZnO and MoS2. Additionally, the quench in the visible region of the PL spectrum of ZnO/MoS2 heterostructures also explains the reduction of the defect in ZnO due to the presence of MoS2.

HiPIMS obtained carbon nano-coatings on copper foil and their thermal conductivity

To prevent overheating of high-power electronic devices, effective cooling and thermal management is a key issue. Owing to the extraordinarily high thermal conductivity of graphene structure in nature, an approach for growth of carbon nano-coating with multiplex layer architecture on copper foil by using high power impulse magnetron sputtering (HiPIMS), as an alternative to the conventional chemical vapor deposition process, is reported for heat-spreading purposes. For successful deposition, a high peak current of 600 A with a short pulse of 30 μs at a relatively low substrate temperature of 600 °C was applied. Moreover, growth mechanisms without and with applying copper for Cu/carbon (Cu/C) nano-coating periodic deposition are revealed and discussed. Based on the measurement results using Angstrom's method, under optimum deposition time, the HiPIMS prepared carbon nano-coating with multiplex layer architecture, which contains in-plane-oriented multilayer graphene structure and the following out-of-plane-oriented turbostratic graphene structure, can enhance the heat spreading ability of the copper foil, reaching a thermal diffusivity value of 1.05 cm2/s. For Cu/C nano-coating periodic deposition, copper can act as catalyzing ingredient to inhibit amorphous carbon formation and promote the crystalline graphene-like structure growth, resulting in a further increase in the thermal diffusivity up to 1.21 cm2/s, twice that of the bare copper foil.

Investigation of the adsorption properties of cyclic C6 molecules on h-BN/Rh(111) surface, efforts to cover the boron nitride nanomesh by graphene

The 2D atomic structure of h-BN would be an excellent dielectric layer to complement graphene electronics. When grown sequentially on metal substrates to create GR/h-BN/metal sandwich structures, these nanomaterials can be used in various applications. To this end, in this project we studied the adsorption and dissociation of cyclohexene and benzene on clean and h-BN covered Rh(111) surfaces at low and at high temperatures. Although we observed that both molecules adsorb on the h-BN/Rh(111) surface at 160 K, there is only a weak interaction between these molecules and h-BN. Moreover, h-BN proved to be completely inert to the split of cyclohexene and benzene after low temperature exposures. In our high temperature experiments, we tested the stability of h-BN towards oxygen, hydrogen and we also followed the effects of high exposure adsorption of the C6 molecules on the nanomesh. We observed a different behavior following the decomposition of the two hydrocarbon species. In one case we developed a graphene-like carbon structure in parallel with BN, while in the other process the carbon layer formed on top of the surface of h-BN/Rh(111). Our results were evidenced by Auger Electron Spectroscopy (AES), High Resolution Electron Energy Loss Spectroscopy (HREELS) and Mass Spectrometry (MS).

Thin Film Coatings from Aqueous Dispersion of Graphene-Based Nanocarbon and Its Hybrids with Metal Nanoparticles

Shungite carbon (ShC) nanoparticles in the form of stable aqueous dispersions represent a promising solution for optical and biomedical applications. The dispersion is an interesting phenomenon from the point of view of stabilization of ShC nanoparticles and their structural constituents up to the basic structural unit, namely a graphene fragment. Herein, we used these aqueous dispersions with easily released structural components to study laser irradiation with various durations and obtain hybrids of ShC with Ag and Au nanoparticles. The main role in the stabilization of ShC nanoparticles belongs to the graphene fragments and their stacks, which display a considerable dipole moment. Newly prepared aqueous dispersions of ShC–metal hybrid nanoparticles retained the stability inherent in the original nanoparticles both of ShC and metals. Changes in the size distribution pattern of nanoparticles in dispersions upon ablation were studied by dynamic light scattering (DLS). Raman with UV-Vis spectroscopy methods were applied to trace structural changes in ShC upon the formation of hybrid nanoparticles. Films obtained by condensation of the dispersions on glass substrates display periodic structures, as was revealed by SEM microscopy. There, the conditions under which nanoparticles lose their ability to disperse in water and retain a graphene-like structure in a film were revealed.

Defect-independent migration of Li on C3B for Li-ion battery anode material

Two dimensional C3B has attracted a lot of attentions due to its graphene-like structure. In this work, the potential of monolayer C3B as anode material of lithium-ion battery are systematically studied through first-principles calculations. The results show that pristine C3B has high stiffness (Young's modulus is 255.65 N/m), good binding strength of Li (−2.55~−2.66 eV), high capacity (1139.96 mA h/g) and good electronic (band gap is 0.64 eV) and ionic conductivity (diffusion barrier is 0.40 eV). It is also found that C3B-VC and C3B-VB has similar cohesive energy and formation energy. Interestingly, C3B shows good defect-independent Li migration capability. The migration barrier of Li on defect C3B was affected slightly by the vacancy, without the trap of Li. Moreover, the vacancy in C3B could improve conductivity and the adsorption ability of Li without the sacrifice of migration ability of Li. These interesting properties indicate that C3B has great potential for the application of anode material for LIBs.

Insight into the effect of clay mineral structure on clay-derived N-doped carbon materials and their efficient electrocatalytic performance

This study aimed to use clay-organic pollutants complex as precursor to fabricate clay-derived N-doped carbon materials, which would reduce the environmental risk of the complex. Kaolinite, sepiolite, montmorillonite as well as iron-saturated montmorillonite were chosen as of the representative clay minerals source. And organic pollutant (tetracycline, TC) was chosen as carbon source. The results revealed the effect of the types of clay minerals and the interaction between TC and clay mineral on the structure and electrocatalytic performance of clay-derived N-doped carbon materials. With the template of layered structural montmorillonite and kaolinite, the obtained carbon materials (NC-MT and NC-KL) possess typically mesoporous structure. With the template of tunnel-like structural sepiolite, NC-SEP exhibited abundant hollow carbon bubbles and mesoporous structure features. Owing to the synergistic effect of iron oxide and montmorillonite in iron-saturated montmorillonite, NC-FEMT showed a graphene-like carbon nanosheet structure with abundant wrinkles and pores. TC might be more easily converted into N-doped clay-derived carbon material, which was partly intercalated into the interlayer of montmorillonite. Besides, the presence of Fe was good for the enhancement of graphitization degree and the generation of active nitrogen species. Moreover, the clay-derived N-doped carbon material presented good oxygen reduction reaction (ORR) electrocatalytic performance.

Heterostructured ZIF-8/lamellar talc composites incorporated polydimethylsiloxane membrane with enhanced separation performance for butanol recovery

In this study, heterostructured MOF/lamellar talc composites was successfully synthesized by in-situ growth of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles on acidified black talc (ABT) and introduced into polydimethylsiloxane (PDMS) matrix to prepare high-performance mixed matrix membranes (MMMs) via spin coating and thermal cross-linking. The submicron-size natural lamellar black talc (BT) was first explored as stable carrier to synthesize laminated composite with continuous MOF phase. Owing to its silica-oxygen tetrahedral structure, the resultant laminated composite presented good compatibility with PDMS matrix, avoiding the formation of interfacial defect between polymer and nanoparticles. Moreover, well-dispersed and continuous ZIF-8 nanoparticles on lamellar nanosheets had preferential adsorption effect for alcohol, enhancing the selectivity of membranes. The coupling effects of graphene-like lamellar structure from talc and sequential transport channels from ZIF-8 attributed to greatly enhance permeation flux. Various techniques such as FESEM, TEM, FTIR, XRD and EDS were applied to investigate the morphology and structure of composites and membranes, and pervaporation experiments were applied to probe the behavior of polymer-based composite membranes. High performance defect-free ZIF-8@ABT/PDMS MMMs exhibited excellent total permeate flux of 1711 g m−2 h−1 with very competitive separation factor of 41 for low concentration n-butanol recovery.

Research on Preparation Methods of Carbon Nanomaterials Based on Self-Assembly of Carbon Quantum Dots.

Here, based on self-assembly of carbon quantum dots (CDs), an innovative method to prepare nanomaterials under the action of a metal catalyst was presented. CDs were synthesized by a one-step hydrothermal method with citric acid (CA) as the carbon source, ethylenediamine (EDA) as the passivator and FeSO4•7H2O as the pre-catalyst. In the experiment, it was found that the nano-carbon films with a graphene-like structure were formed on the surface of the solution. The structure of the films was studied by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR), etc. The results demonstrated that the films were formed by the self-assembly of CDs under the action of the gas–liquid interface template and the metal catalyst. Meanwhile, the electrochemical performance of the films was evaluated by linear cyclic voltammetry (CV) and galvanostatic charge discharge (GOD) tests. In addition, the bulk solution could be further reacted and self-assembled by reflux to form a bifunctional magnetic–fluorescent composite material. Characterizations such as X-ray diffractometer (XRD), fluorescence spectra (FL), vibrating sample magnetometer (VSM), etc. revealed that it was a composite of superparamagnetic γ-Fe2O3 and CDs. The results showed that self-assembly of CDs is a novel and effective method for preparing new carbon nanomaterials.

Hydrothermal functionalization of graphene quantum dots extracted from cellulose

Functionalization is a promising approach to modify the physical and chemical properties of graphene quantum dots (GQDs). However, the synthesis of functionalized GQDs (F-GQDs) is usually conducted with strong acids. Thus, the sustainable synthesis route of F-GQDs remains a challenge. This is important for suitable optimization of GQDs to be applied in sustainable photovoltaic applications, especially dye-sensitized solar cells owing to the strong attachment of functional group elements. This study presents a detailed study of optical, structural, and chemical changes that occurred in GQDs during the functionalization process by adding an ionic liquid, 1-ethyl-1-methylpyrrolidium bis(trifluoromethylsulfonyl)imide via hydrothermal synthesis approach using an eco-friendly route comprising only cellulose and deionized (DI) water. The presence of ionic liquid provides fundamental elements (nitrogen (N), fluorine (F), and sulfur (S)), which are added to GQDs producing F-GQDs. The optimum result shows that the 20 wt% N, F, S functionalized GQDs have the largest UV–vis absorption and photoluminescence emission. The F-GQDs also revealed a single crystalline hexagonal graphene-like honeycomb structure in transmission electron microscopy and increased roughness relatively from atomic force microscopy. Moreover, the Fourier transform infrared and x-ray photoelectron spectroscopy have also confirmed the presence of C-N, C=S, C-F, and N-H functional groups in the F-GQDs produced.

Improvement in Structure and Visible Light Catalytic Performance of g-C3N4 Fabricated at a Higher Temperature

A highly-efficient graphitic carbon nitride (g-C3N4) photocatalyst for visible light photodegradation of rhodamine B (RhB) and methyl orange (MO) simulating dyeing wastewater was synthesized by the thermal polycondensation of melamine. The photocatalysts were characterized by TG-DTG-DSC, XRD, EA, XPS, FT-IR, SEM, TEM, BET, PL and UV-vis DRS. The results showed that the photocatalytic performance of g-C3N4 at a higher calcination temperature was significantly enhanced, and its photocatalytic activities for the photodegradation of RhB and MO were remarkably improved by 64.91% and 41.83%, respectively, which was mainly attributed to the satisfactory crystallinity, stable graphene-like structure, large surface area, and excellent optical properties. It was found that •O2− radicals and •OH radicals were the main active species for the photodegradation process by the free radicals trapping experiments and ESR analysis. The photodegradation mechanism of g-C3N4 was proposed predicated using the characterization results.

Zn and N co-doped porous carbon nanosheets for photothermally-driven CO2 cycloaddition

Solar energy is considered as the cleanest, cheapest, and most sustainable energy source, and CO2 cycloaddition that is drove by solar energy has unique advantages in the aspect of energy and environmental. Therefore, Zn and N co-doped porous carbon nanosheets (ZNCs), which were synthesized by a simple one-step pyrolysis method, as catalysts and photothermal material to photothermally drive cycloaddition of CO2. The prepared ZNCs show graphene-like layered structure, uniformly distributed Lewis acid (Zn atoms) sites and Lewis base (N atoms) sites, full spectrum absorption and high photothermal conversion efficiency. More importantly, ZNCs have a higher catalytic efficiency than traditional heating methods because it can be quickly in-situ heated by light, hence the yield of cyclic carbonate reached 91.1% (0.1 MPa CO2, 1000 mW·cm−2 full-spectrum irradiation, 12 h). ZNCs were recycled five times without significant reduction in catalytic efficiency, and have high activity to other series of epoxides. A possible CO2 cycloaddition mechanism which is catalyzed by ZNCs is proposed, including the step of adsorption, ring opening, insertion and cyclic carbonates formation.