N-doped Graphene Research Articles

Enhancement of Mechanical and Chloride Binding Properties in Seawater Cement Using a Novel Carbon Nanomaterial

Chloride binding technology can effectively reduce the content of free chloride ions in seawater (used for cementitious materials), thereby extending the service life of seawater concrete structures. Currently, affordable and highly dispersed nanomaterials that can enhance the chloride binding capability of seawater cement are finite. This paper presents the first experimental study on N-doped graphene quantum dots (NGQDs), an innovative carbon nanomaterial with low price and high dispersibility, to strengthen the mechanical and chloride binding capabilities of seawater cement. Concretely, NGQDs are prepared through the hydrothermal process. The morphology and structure of NGQDs are measured by TEM, AFM, FTIR, and XPS. And the strengths and chloride binding performance of different specimens are analyzed by compressive/flexural strength tests and chloride adsorption equilibrium tests. The phase compositions of various specimens are analyzed by XRD, TGA/DTG, and SEM. The consequences indicate that the unique structure of the prepared NGQDs endows them with excellent water solubility and dispersibility. Notably, the introduction of NGQDs enhances the mechanical performance of seawater cement and 0.05 wt.% NGQDs have the greatest improvement effect. The compressive and flexural strengths of seawater cement containing 0.05 wt.% NGQDs increase by 8.21% and 25.77% after 28 d curing, respectively. Additionally, the seawater cement containing 0.2 wt.% NGQDs have the best chloride binding capability and are 41.08% higher than the blank group. More importantly, the chloride binding mechanism is that NGQDs accelerate seawater cement hydration, resulting in an increased formation of hydrated calcium silicate (C–S–H) and Friedel’s salt (Fs), thereby strengthening the physisorption and chemical combination of chloride. This study highlights an inexpensive and highly dispersible nanomaterial to heighten the stability of seawater concrete structures, opening up a new path for the better utilization of seawater resources.

Blue Luminescence from N-doped Graphene

Abstract Blue luminescence (BL) has been observed in various astrophysical environments, such as the inner region of the Red Rectangle Nebula. It has been previously linked to small polycyclic aromatic hydrocarbons. In this study, we explore the potential of N- and O-doped graphene material as carriers of BL. Using vacuum ultraviolet irradiation, pristine single-layer graphene films were exposed to solid N2 and O2 at low temperatures, resulting in the formation of N- or O-doped graphene. The photoluminescence (PL) spectrum of the synthesized N-doped graphene exhibits an asymmetrical peak at 378 nm, which is nearly identical to the BL observed in the Red Rectangle. In contrast, the synthesized O-doped graphene shows a symmetrical PL band at 414 nm. Further Raman and X-ray photoelectron spectroscopy analyses reveal that nitrogen atoms substitute carbon atoms in the graphene lattice, introducing structural defects and sp2 regions responsible for the observed luminescence. The simplicity of the bonding structures in the N-doped graphene, dominated by pyrrolic-N and pyridinic-N groups, further supports its potential as a model system for studying BL.

Synergistic Effect of CNT and N-Doped Graphene Foam on Improving the Corrosion Resistance of Zn Reinforced Epoxy Composite Coatings

The synergistic effect of CNT and three-dimensional N-doped graphene foam (3DNG) on improving corrosion resistance of zinc-reinforced epoxy (ZRE) composite coatings was studied in this work. Although CNT itself was demonstrated to be effective to promote the anti-corrosion performance of the ZRE coating, the incorporation of additional 3DNG leads to further enhancement of its corrosion resistance under the synergistic effect of the hybrid carbon nanofillers with different dimensions. Both the content of the carbonaceous fillers and the ratio between them affected the performance of the coating. The optimal content of hybrid filler in the coating was determined to be only 0.1% with 3DNG:CNT = 1:3. With the modification of hybrid fillers, the corrosion current of the coating could be reduced by more than six orders of magnitude. Additionally, the immersion test of the pre-scratched coating directly demonstrated the evident contribution of the hybrid fillers to the sacrificial anode-based surface protection mechanism of the coating. These results confirmed the synergistic effect of the hybrid 1D and 3D carbonaceous fillers on promoting the corrosion inhibition of their coating, which could be promising for application in other functional composites.

Biocompatible Carbon Dots/Polyurethane Composites as Potential Agents for Combating Bacterial Biofilms: N-Doped Carbon Quantum Dots/Polyurethane and Gamma Ray-Modified Graphene Quantum Dots/Polyurethane Composites

Background: Pathogen bacteria appear and survive on various surfaces made of steel or glass. The existence of these bacteria in different forms causes significant problems in healthcare facilities and society. Therefore, the surface engineering of highly potent antimicrobial coatings is highly important in the 21st century, a period that began with a series of epidemics. Methods: In this study, we prepared two types of photodynamic polyurethane-based composite films encapsulated by N-doped carbon quantum dots and graphene quantum dots irradiated by gamma rays at a dose of 50 kGy, respectively. Further, we investigated their structural, optical, antibacterial, antibiofouling and biocompatibility properties. Results: Nanoelectrical and nanomechanical microscopy measurements revealed deviations in the structure of these quantum dots and polyurethane films. The Young’s modulus of elasticity of the carbon and graphene quantum dots was several times lower than that for single-walled carbon nanotubes (SWCNTs) with chirality (6,5). The electrical properties of the carbon and graphene quantum dots were quite similar to those of the SWCNTs (6,5). The polyurethane films with carbon quantum dots were much more elastic and smoother than the films with graphene quantum dots. Antibacterial tests indicated excellent antibacterial activities of these films against a wide range of tested bacteria, whereas the antibiofouling activities of both composite films showed the best results against the Staphylococcus aureus and Escherichia coli biofilms. Biocompatibility studies showed that neither composite film exhibited any cytotoxicity or hemolysis. Conclusions: Obtained results indicate that these composite films could be used as antibacterial surfaces in the healthcare facilities.

High-throughput screening of a transition metal single-atom electrocatalyst for the CH3NO2 reduction reaction

The hydrogenation reduction of nitro compounds involves the wide application of functional amines as important chemical intermediates in the fine chemical industry. However, the development of low-cost, mild reaction conditions and high-performance catalysts for the reduction of nitro compounds is challenging. In this study, the potential of electrocatalysts in which 26 transition metal atoms are anchored to the surface of N-doped graphene (TMN4@G) was explored to determine the mechanism of the electrocatalytic CH3NO2 reduction reaction (CNORR) via density functional theory. First, the stability of TMN4@G was evaluated to screen out the catalyst which is stable at 300 K via ab initio molecular dynamics. Second, the Gibbs free energy with all possible reaction pathways of the CNORR was calculated to search for high-performance catalysts. These results demonstrate that monodentate adsorbed CdN4@G, FeN4@G, CoN4@G and bidentate adsorbed MoN4@G exhibit excellent catalytic activity. The overpotential of MoN4@G is only 0.357 V. Finally, Finally, the role of central metal atom on the catalytic activity of single-atom catalysts in CNORR and the impact of hydrogen evolution reaction on the adsorption of CH3NO2 were further discussed. We hope that this theoretical simulation provides an effective scheme for the reduction of nitro compounds under mild conditions.

Mechanistic insight into the catalytic activities of metallic sites on nitrogen-doped graphene quantum dots for CO2 hydrogenation

The origin of selectivity and activity of the CO2 hydrogenation reaction on single-atom catalysts composed of three adjacent 3d transition metals (Fe, Co, and Ni) supported on N-doped graphene quantum dots were systematically investigated and compared using density functional theory (DFT) calculations, natural bond orbital (NBO), and quantum theory of atoms in molecules (QTAIM) analysis. This study reveals that π-backbonding between the metal and CO2* does not occur and [CO2]δ+ species drive the reaction. The CO2* reacts with H2 via the Eley-Rideal (ER) mechanism by using the synergistic effects of the N site. The higher the partial positive charge on the C atom, the lower the Ea of the reaction. Subsequently, a tautomerization reaction, which is facilitated by hydrogen bonding, occurs and hydrogen is transferred to HCOO* resulting in the formation of CHOOH*. This study shows the selective formation of formic acid from CO2 is accessible on these SACs and Fe-SAC is the best one between these three catalysts. Although CO2 is more inert than formic acid the H2 molecule reacts with the adsorbed formic acid more difficult than the adsorbed CO2. It is because the hydrogenation of formic acid causes C-H bond formation resulting in failure of the coordinated O atom's octet and the unstable H2COOH* is formed. This step is the rate-determining step of HOCH2OH formation from CO2, with Ea of 1.94, 2.03, and 2.23 eV for Fe, Co, and Ni, respectively. Finally, the system undergoes another tautomerization reaction resulting in the formation of HOCH2OH (formaldehyde monohydrate).

Single-Entity Electrochemistry of N-Doped Graphene Oxide Nanostructures for Improved Kinetics of Vanadyl Oxidation.

N-doped graphene oxides (GO) are nanomaterials of interest as building blocks for 3D electrode architectures for vanadium redox flow battery applications. N- and O-functionalities have been reported to increase charge transfer rates for vanadium redox couples. However, GO synthesis typically yields heterogeneous nanomaterials, making it challenging to understand whether the electrochemical activity of conventional GO electrodes results from a sub-population of GO entities or sub-domains. Herein, single-entity voltammetry studies of vanadyl oxidation at N-doped GO using scanning electrochemical cell microscopy (SECCM) are reported. The electrochemical response is mapped at sub-domains within isolated flakes and found to display significant heterogeneity: small active sites are interspersed between relatively large inert sub-domains. Correlative Raman-SECCM analysis suggests that defect densities are not useful predictors of activity, while the specific chemical nature of defects might be a more important factor for understanding oxidation rates. Finite element simulations of the electrochemical response suggest that active sub-domains/sites are smaller than the mean inter-defect distance estimated from Raman spectra but can display very fast heterogeneous rate constants >1cms-1. These results indicate that N-doped GO electrodes can deliver on intrinsic activity requirements set out for the viable performance of vanadium redox flow battery devices.

Synergistic effects of metal single atoms and clusters on graphene-supported electrocatalysts: Insights into the mechanism of oxygen reduction reaction

In recent years, non-precious-metal-doped single-atom catalysts have emerged as promising alternatives to Pt-based catalysts due to their high active site density and excellent oxygen reduction reaction (ORR) activity. However, challenges arise in precisely controlling the doping precision of metal atoms during experimental preparation, often resulting in clustering of metal atoms. The impact of these metal clusters on catalytic activity remains unclear. Here employing density functional theory, we investigated a series of N-doped graphene based catalysts, including MN4, MN4@M4˗Py, MN4@M4˗Qu (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Ir, Pt), to elucidate changes in catalyst properties upon metal cluster loading and assess how different configurations of metal clusters influence ORR activity. Our findings reveal synergistic interactions between metal clusters and single atoms, which can either enhance or inhibit catalytic activity depending on elemental types and cluster configurations. Remarkably, the CoN4@Co4˗Py catalyst exhibits superior ORR catalytic performance, with an overpotential of 0.277 V. This study not only sheds light on the synergistic effects between metal clusters and catalysts, but also offers theoretical insights for the experimental preparation of catalysts.

Chemical changes from N-doped graphene and Metal-Organic Frameworks to N-G/MOF composites for improved electrocatalytic activity

Integrating N-doped graphene (N-G) with Metal-Organic Frameworks (MOFs) enhances catalytic activity for oxygen reduction reaction (ORR), often exceeding both the performances of their precursors and, in some cases, even Platinum group metal (PGM)-based catalysts. However, the factors driving this improved catalytic activity in N-G/MOF composites remain unexplored, particularly from the perspective of the chemical changes. To investigate the chemical changes in N-G and MOF upon their integration and the implications of these changes on ORR catalytic activity, an N-G/MOF was synthesized from N-G with a MOF (ZIF-8) following a mechanochemical wet ball milling process. The N-G, ZIF-8, and N-G/MOF samples were examined for changes in elemental composition, chemical state of carbon, different nitrogen and carbon bonds, and other chemical interactions. In the N-G/MOF catalyst, compared to its N-G and ZIF-8 precursors, the relative oxygen content increased, indicating the formation of additional oxygen-containing groups. The C 1s peak shifted to a lower binding energy in N-G/MOF, suggesting changes in the overall chemical or oxidation state of the carbon atoms. Besides, the increase in pyridinic-N functional groups in N-G/MOF points to the formation of additional active sites. Furthermore, the formation of C–Zn bonds in N-G/MOF suggests the probable emergence of single-atom Zn sites, while the increase in CO bonds points to the formation of carboxyl or carbonyl groups. These chemical changes could be linked to the enhanced electrocatalytic activity of the N-G/MOF composite for ORR. This study may also be beneficial for other research focused on developing composite catalysts involving various N-G and MOFs-based materials.

Fe3O4 nanoparticles decorated on N-doped graphene oxide nanosheets for elimination of heavy metals from industrial wastewater and desulfurization

Finding an effective and excellent pertinent single catalyst material for multipurpose application for the purification of hydrocarbons in fuels (desulfurization), and for efficient removal of heavy metals from industrial effluent is greatly endowed. In the present work, a hybrid nanocomposite of ultrafine magnetite (Fe3O4) nanoparticle embedded on the surface of in-situ nitrogen doped layered GO (NGO) sheets were fabricated by sol-gel method and treatment with microwave irradiation technique is reported for the first time. The results show a high removal efficiency of 97 % for multiple heavy metals (Pb2+, Cd2+, Cu2+, Cr+2, Mn+2etc.) in industrial effluent and as well as in synthetic water with a very good retention performance of 99 %. The composites were tested against the elimination of sulfur from thiophene is 1.495 mmol g−1 is reported high is due to coupling and coordination of nitrogen with FeO and C. Recycling studies showed that the developed composites had excellent recyclability, with <82 % removal at the 5th cycle; its feasibility was evaluated using industrial effluent water and in synthetic water. Surface phenomena studies presented here revealed that the adsorptive removal processes of heavy metals involved π electron donor-acceptor interactions, ion exchange, and electrostatic interactions, along with surface complexation that showed an excellent synergism. A high stability, and retention performance is better than the pure Fe3O4 and NGO sheets. We hope that this study will motivate and give further scope for scientists working on magnetite-based graphene nanocomposites.

Interface engineering of heterostructural quantum dots towards high-rate and long-life lithium-sulfur full batteries

Despite being as next-generation energy storage systems with ultra-high theoretical energy density of 2600 Wh kg−1, lithium-sulfur (Li-S) batteries face serious hurdles due to the sluggish redox kinetics in S cathodes and uncontrollable growth of dendrites in Li anodes. To simultaneously address such issues, herein, we present an interface engineering strategy to develop a dual-functional host for S cathode and Li anode, which is constructed by heterostructural WC-WN0.67 quantum dots homogeneously embedded in N-doped graphene nanosheets (WC-WN0.67@NG). As a result, the Li-S full batteries deliver a high reversible capacity of 704 mA h g−1 even at a high rate of 4 C, and demonstrate a long-term cycling stability even at 2 C with a low degradation rate of 0.027 % over 1200 cycles. This work paves the way to facilitate the practical applications of Li-S batteries through interface engineering of dual-functional heterostructural quantum-dot host.

Graphene-based chemiresistive hydrogen sensor for room temperature operation

Taking advantage of ultraviolet (UV) irradiation to clean the surface and tuning the charge carriers of graphene, n-doped graphene shows excellent hydrogen sensing capabilities. With assistance of a 265 nm UV light irradiation, the response time of sensor reaches 3 s to 5 ppm hydrogen. And after being relented in ambient condition for a year, it still maintains nearly identical performance. Furthermore, by adding PMMA layer as molecular sieve, the sensor can effectively shield against humidity changes, exhibiting high selectivity towards hydrogen. When the relative humidity varies within the range in 20–70 %, the sensor basically maintains similar response performance. This work streamlines the preparation process of hydrogen sensors and introducing exceptional selectivity with the help of a molecular sieve, facilitating the practical application of hydrogen sensors.

Preparation of bifunctional oxygen evolution reaction and oxygen reduction reaction catalyst CoO-TiO2@NG by high gravity-hydrothermal method for rechargeable Zn air battery

For rechargeable Zn air batteries (ZABs), the low cost and scalable preparation method for the catalyst with favorable bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalytic properties is a critical influence factor for its large-scale application. In this paper, the composites (preTiO2@hG) consisting of the precursor of titanium dioxide and hydrophilic graphene were successfully prepared in a Rotating Packed Bed by high-gravity technology. Then, N and Co elements were doped by hydrothermal-reduction method to obtain composite catalyst CoO-TiO2@NG, which had excellent catalytic performances of both OER/ORR. The value of ΔE is 0.685 V for CoO-TiO2@NG. When used as the catalyst on the air cathode of rechargeable ZABs, the device exhibits a high power density of 146.8 mW/cm2 and a large specific capacity of 815.8 mAh/g. It also has good cycle stability, the ZAB capacity using CoO-TiO2@NG as catalyst does not significantly decrease after more than 110 h of charging-discharging cycles. The improvement of OER and ORR catalytic performance of CoO-TiO2@NG is due to the synergistic effect of CoO, TiO2 and N-doped graphene. This article provides a new method for low-cost and scalable preparation of bifunctional OER/ORR non-precious metal catalysts with novel component and high performances.

Ultrafine Mo2N Quantum Dots Embedded in N-Doped Graphene Sheets Enable Efficient Adsorption-Catalytic Transformation of Polysulfides.

Because of the high theoretical energy density of 2600 Wh kg-1, lithium-sulfur batteries (LSBs) are anticipated to be among the next generation of high-energy-density storage technologies. However, the practical application of LSBs has been severely hampered by the significant shuttle effect and slow redox kinetics of polysulfides (LiPSs). To address the above problems, in this paper, the concept of quantum dots (QDs) was introduced to design and synthesize Mo2N QD-modified N-doped graphene nanosheets (marked as Mo2N-QDs@NG), which were used as separator modification materials for LSBs. The experimental results demonstrated that the introduction of Mo2N QDs avoids stacking of graphene sheets and provides more active sites for the conversion of LiPSs. Moreover, Mo2N enhances the chemical fixation and catalyzes the liquid-solid conversion of soluble LiPSs by forming Mo-S and Li-N bonds with LiPSs. Additionally, establishing Mo-C bonds with Mo2N, N-doped graphene sheets can facilitate the transport of electrons and ions and physically prevent the diffusion of LiPSs, thus creating a highly conducting carbon structure to support electrochemical reactions. Benefiting from the synergistic effect of chemical immobilization and catalysis of Mo2N QDs with the physical confinement of NG, Mo2N-QDs@NG-PP batteries exhibit enhanced electrochemical performance.

Single-Atom Underpotential Deposition at Specific Sites of N-Doped Graphene for Hydrogen Evolution Reaction Electrocatalysis

Single-atom catalysts (SACs) have the advantages of good active site uniformity, high atom utilization, and high catalytic activity. However, the study of its controllable synthesis still needs to be thoroughly investigated. In this paper, we deposited Cu SAs on nanoporous N-doped graphene by underpotential deposition and further obtained a Pt SAC by a galvanic process. Electrochemical and spectroscopic analyses showed that the pyridine-like N defect sites are the specific sites for the underpotential-deposited SAs. The obtained Pt SAC exhibits a good activity in a hydrogen evolution reaction with a turnover frequency of 25.1 s−1. This work reveals the specific sites of UPD of SAs on N-doped graphene and their potential applications in HERs, which provides a new idea for the design and synthesis of SACs.

Electrochemical CO2 reduction on Single-Atom aluminum catalysts supported on graphene and N-doped Graphene: Mechanistic insights and hydration effects

By means of periodic density functional theory calculations, we have investigated the electrochemical reduction of carbon dioxide (CO2RR) on single-atom aluminum catalysts anchored on graphene substrates (Al-3C-graphene and Al-3N-graphene). The predominant path of CO2RR on Al-3C-gra proceeds via the HCOO* intermediate, with the possible products HCOOH* and CH3OH* tightly controlled at the Al site until the formation of CH4. The potential determining step (PDS) is the conversion of HCOOH* to CH2OOH*, an endergonic process requiring 0.33 eV. The Al site of Al-3N-gra exhibits strong binding with the COOH* and HCOO* intermediates; however, the formation of HCOO* still prevails. The PDS becomes the conversion of HCOO* to H2COO*, with a limiting potential (UL) of –0.22 V, resulting in the formation of an OH* species occupying the Al site. Regardless of whether it is on Al-3C or Al-3N, the water molecules generated during CO2RR will be firmly adsorbed onto the aluminum center. Therefore, we also considered CO2RR on hydrated Al-3C and Al-3N-gra. After three water molecules bind with Al-3C and Al-3N, the former will maintain a (H2O*)3-Al-3C-gra complex, while the latter will release a proton and form a (H2O*)2(OH*)-Al-3N-gra complex, which is highly exothermic. The UL of CO2RR on (H2O*)3-Al-3C-gra is reduced to –0.26 V compared to clean Al-3C-gra, indicating that the adsorption of water effectively regulates the relative Gibbs free energy of the intermediates. The UL of CO2RR on (H2O*)2(OH*)-Al-3N-gra becomes –0.72 V, which is higher than the clean Al-3N-gra counterparts. However, the hydrated Al-3N-gra still maintains a great CO2 capture ability.

Modality-Tunable Exfoliated N-Doped Graphene as Effective Electrolyte Additive for High-Performance Lithium-Sulfur Batteries.

While chemically doped graphene has shown great promise, the lack of cost-effective manufacturing has hindered its use. This study utilizes a facile fabrication approach for modality-tunable N-doped graphene via thermal annealing of aqueous-phase-exfoliated few-layered graphene from a Taylor-Couette reactor. This method demonstrates a high level of N-doping (27 atom % N) and offers modality tunability of the C-N bond without foregoing scalability and green chemistry principles. The resulting N-doped graphene, with varying N content and doping modality, is utilized in the lithium-sulfur battery electrolyte to address low ionic conductivity, lithium polysulfide (LiPS) shuttling, and Li anode instability. The study reveals that higher N content and pyridinic N modality graphene in the electrolyte positively influence battery performance. The results are 2-fold: higher overall N content improves capacity retention (73%) after 225 cycles at 0.2 C, and pyridinic-type nitrogen demonstrates the best performance at high C rates, exhibiting a 4-fold capacity increase relative to the reference cell at 2 C. Further, the computational study validates the adsorption affinity of LiPS to pyridinic nitrogen and improved Li+ mobility on the graphene backbone observed experimentally. This first experimental study on the impact of N-dopant concentration and modality on electrochemical performance provokes insights into tailoring N functionalization to achieve superior electrochemical performance.

Rare-earth metal neodymium anchored into graphene as a promising CO2 reduction electrocatalyst by regulating the coordination environment

Carbon-based single atom catalysts (SACs) are promising electrocatalysts in the field of carbon dioxide reduction reactions (CO2RR) due to their high efficiency and environmental friendliness, in which the coordination environment is the key factor determining their intrinsic catalytic activity. Furthermore, rare-earth-based SACs have shown great potential on CO2RR in recent years. Meanwhile, various studies have focused on combining metals with N-doped graphene, which together form potential Mx-Ny-C active sites. This work systematically investigates the impact of varying N/C coordination numbers on Nd atoms in graphene (Nd-NxC6-x, x = 0–5) on the CO2RR reaction mechanism and catalytic performance through density functional theory methods. Detailed Gibbs free energy calculation results indicate that most catalysts undergo a two-electron reduction pathway. For Nd-N3C3, Nd-N3C3–1, Nd-N3C3–2, Nd-N4C2, Nd-N4C2–1, Nd-N4C2–2, and Nd-N5C, HCOOH is the main product, with low UL values of -0.18, -0.17, -0.03, -0.10, -0.11, -0.09, and -0.10 V, respectively. In summary, our research results not only indicate that N atoms with different coordination numbers can improve the product selectivity and catalytic activity of catalysts, but also may provide valuable theoretical insights for studying the application of rare-earth-based SACs.

First-principles study of O3 molecule adsorption on pristine, N, Ga-doped and -Ga-N- co-doped graphene

The adsorption of O3 molecules (ozone) on graphene, N-doped graphene, Ga-doped graphene, and -Ga-N- co-doped graphene with an emphasis on O3 detection was examined in this work. The physical characteristics of -Ga-N-co-doped graphene are significantly altered upon O3 adsorption, which makes it a suitable choice for O3 detection molecular sensors. The interaction between the O3 molecule and the adsorbent is explained on the basis of their adsorption energy, adsorption distance and charge transfer. It was found that the adsorption of ozone molecules on the -Ga-N- co-doped graphene was more favorable in energy than that on the pristine one, representing the superior sensing performance of -Ga-N- co-doped system. In our work, we estimated the charge transfer between the O3 molecule and doped graphene nanostructures based on Mulliken population analysis. The calculated adsorption energy value shows the ozone molecule more firmly adsorbs on the surface of -Ga-N- co-doped graphene nanostructures (Eads = –1.74 eV) than that of pristine graphene (Eads = –0.41 eV), deriving from a stronger covalent bond between the ozone molecule and the -Ga- N- co-doped graphene nanostructures. Our findings thus suggest that -Ga-N- co-doped graphene could be a highly efficient gas sensor device for O3 detection in the environment.

Fibrous catalyst based on atomic Pd and N-doped holey graphene functionalized cotton fiber for continuous-flow reaction

Continuous-flow catalysis bridges the gap between bench-scale laboratories and production-scale factories and thus should be a green and promising technology for the manufacture of value-added chemicals. Here, we present the construction of a continuous-flow catalytic system by integrating a tubular reactor with novel catalytic fibers, which are comprised of single-atomic Pd (Pd1) and nitrogen-doped holey graphene (NHG) functionalized cotton fibers (CFs). Due to the loosely packed structure, highly exposed dual-active sites (i.e., single-atomic PdN4 sites and activated C sites in the NHG carbocatalyst) of the CF@(Pd1/NHG) catalytic fibers, the corresponding flowing system exhibites remarkably high catalytic performance (activity and durability) and processing rate in organic reactions, including oxidative hydroxylation of phenylboronic acid and reduction of nitroarenes. Typically, the processing rate of the catalytic system toward 4-nitrophenol (a representative nitroarene) reduction can reach up to 2.46 × 10−3 mmol·mg−1·min−1, significantly higher than that of those packing catalysts reported in recent years.