Amount Of Nitrogen Doping Research Articles

Polarity on adsorption and photocatalytic performances of N-GR/TiO2 towards gaseous acetaldehyde and ethylene

The surface adsorption is considered to be a very important factor in photodegradation process, especially in the removal of gaseous pollutants. In this work, nitrogen doped reduced graphene (N-GR)/TiO2 were synthesized to probe the polarity adsorption and photodegradation characteristics of acetaldehyde (polar) and ethylene (nonpolar). Morphology and properties of the samples were revealed by TEM, Raman spectra, photoluminescence spectra, photocurrent, electron spin resonance and so forth. Adsorption of flowing gas and TPD were used to indicate the adsorption ability of the composites towards acetaldehyde and ethylene. In experiments, the difference of nitrogen doping amount can adjust the polarity of N-GR/TiO2 composites efficiently and then influence their photodegradation performance. Specifically, the N-GR/TiO2 showed higher acetaldehyde adsorption capacity than GR/TiO2, while the GR/TiO2 possessed the highest adsorptive abilities in ethylene case. In the subsequent photodegradation tests of flowing acetaldehyde, all of the N-GR/TiO2 samples had removal efficiencies higher than that of GR/TiO2. The highest removal efficiency reached by the 2 N-GR/TiO2 is around 82%. In the ethylene to contrast, the removal efficiency was obtained as 93.8% by GR/TiO2, which is higher than that of the N-doped samples. It can be seen that the high polarity samples could improve the adsorption and photodegradation performance of polar molecules, which could propel the understanding and application of photodegradation technologies.

Highly fluorescent near-infrared emitting carbon dots derived from lemon juice and its bioimaging application

Fluorescent carbon dots (CDs) have gained intensive interests in the recent years due to their unique optical properties and widespread applications. However, the facile synthesis of highly efficient near-infrared emitting CDs (NIR-CDs) from renewable and low-cost natural resources is still a challenge to be addressed for their further applications, particularly in the bioimaging fields. Herein, NIR-CDs with a high quantum yield of 31% in water were synthesized by heating a formamide solution of pulp-free lemon juice. The as-obtained NIR-CDs possess an average size of 5.7 nm and a nitrogen content of approximately 20%, and exhibit an excitation-independent photoluminescence (PL) emission at 704 nm. Further studies suggest that the intense near-infrared emission of NIR-CDs is originated from their surface states, and that the energy gaps of these surface states are modulated by both the particle size and the nitrogen-doping amount. In addition, characterized with good photostability and low cytotoxicity, these NIR-CDs can be used as an excellent fluorescent probe for bioimaging both in vitro and in vivo.

In-situ growth of nitrogen-doped mesoporous carbon nanostructure supported nickel metal nanoparticles for oxygen evolution reaction in an alkaline electrolyte

Rational three-dimensional nitrogen doped mesoporous carbon nanostructured surfaced Nickel metal (Ni) nanoparticles (nps), NCNP composites have been developed using nickel organic complex and utilized as an electrocatalyst for oxygen evolution reaction. The NCNP composites of tunable physio-chemical characteristics, such as Ni nps size (∼18–∼42 nm), surface area (∼18–∼43 m2 g−1), pore size (3.23–3.84 nm) and nitrogen doping amount (1.20–3.87 wt%) have been achieved via controlled carbonization temperature. An optimized NCNP composite of favorable physio-chemical properties has delivered good oxygen evolution kinetics such as a lower overpotential value (370 mV) at 10 mA cm−2, a minimum Tafel slope value (55 mV dec−1), and relatively a higher electrochemical surface area (0.6325 cm−2) than the other NCNP composites. Moreover, the best NCNP electrocatalyst has shown a comparable overpotential value with the benchmarking catalyst at 10 mA cm−2, equivalent to ∼10% solar photoelectrical conversion efficiency. In addition, the best NCNP electrocatalyst has exhibited excellent accelerated degradation test for 24 h at a constant current density of 10 mA cm−2 with an increase overpotential value of 0.029 V.

Novel High Capacity Cathode Materials Based on Li-Rich Cathode Materials By Nitrogen-Doping

Introduction Lithium-rich materials are strong candidates for the next generation cathode because of their higher theoretical capacity over 300 mAh g-1[1]. It has been reported that the charge compensation mechanism of the lithium-rich cathode is consisted of both 3d and/or 4d transition metal cation and oxide anion redox reaction [1], and the use of anionic redox leads to the large capacity. The electrode performance is profoundly influenced by the electronic state of transition metals and oxide ions [2]. Stabilizing the anionic redox is a promising approach to design and develop the new cathode materials with high energy density. The previous researches are mainly focused on the effect of transition metals, like 3d-trantision metal Li2MnO3 and 4d-transition Li2RuO3 [3]. The difference of transition metal changes electronic states of oxide ions and cations, greatly affecting the electrode performance. This work offers different perspectives from previous works, doping another anion to the Li-rich cathode materials to control the electronic structure of anion. The cation-disordered rock salt type Li1.2Ti0.4Mn0.4O2 cathode [4] and new N-doped cathode materials Li1.2Ti0.4Mn0.4O1.93N0.05 and Li1.2Ti0.4Mn0.4O1.85N0.10 were synthesized and the electrochemical performance were measured to estimate the effect of nitrogen-doping to the Li-rich cathode materials. Experimental The cathode materials Li1.2Ti0.4Mn0.4O2-0.015xN0.01x (x=0, 5 and 10) were synthesized by dry mechanical ball-milling. The cathode was prepared from a paste by mixing 70 wt% of as-prepared active materials, 20 wt% of acetylene black and 10 wt% of polyvinylidene difluoride binder in 1-methyl-2-pyrrolidone solvent and then this paste was coated on the Al foil. Li foil used as the counter electrode material and 1 mol dm-3 LiPF6 in an acetonitrile solvent was used as an electrolyte. 2032-type coin cells were assembled in the Ar-filled glove box. The galvanostatic charge discharge measurements were operated at 50 °C or room temperature. Results and Discussion The XRD pattern confirmed that each cathode materials have single-phase cation-disordered rocksalt structure. The diffraction peaks are shifted to lower angle with increasing the amount of nitrogen doping, indicating the increasing of lattice constant. The 1st charge of Li1.2Ti0.4Mn0.4O2 exhibited a plateau about 4.5 V as previously reported [4], and about 280 mAh g-1 capacity at C/20 rate. In the subsequent discharge process, the cathode material exhibited 220 mAh g-1. On the other hand, the N-doped cathode Li1.2Ti0.4Mn0.4O1.85N0.10 exhibited about 350 mAh g-1 charge capacity and 280 mAh g-1 discharge capacity during 1st cycling. These results suggest that nitrogen doping improves practical capacity and cycle performance in the Li1.2Ti0.4Mn0.4O2 series. The improvement mechanism of the electrochemical performance will be discussed in the presentation. Reference s [1] M. Oishi, T. Fujimoto, Y.Takanashi, Y.Orikasa, A. Kawamura, T. Ina, H. Yamashige, D. Takamatsu, K. Sato, H. Murayama, H. Tanida, H. Arai, H. Ishii, C. Yogi, I,Watanabe, T. Ohta, A. Mineshige, Y. Uchimoto and Zempachi Ogumi, J. Power Sources, 222, (2013) 45 [2] K.Luo, M R. Roberts, R. Hao, N. Guerrini, D M. Pickup, Y-S. Liu, K. Edstroem, J. Guo, A V. Chadwick, L C. Duda and P G. Bruce, Nat. Chem. 2016, 8, 684. [3] M, Sathiya, K. Ramesha, G. Rousse, D. Foix, D. Gonbeau, A.S. Prakash, M. L. Doublet, K. Hemalatha and J-M. Tarascon, Chem. Mater., 25, (2013) 1121 [4] N.Yabuuchi, M.Nakayama, M. Takeuchi, S. Komaba, Y. Hashimoto, T. Mukai, H. Shiiba, K. Sato, Y. Kobayashi, A. Nakao, M. Yonemura, K. Yamanaka, K. Mitsuhara and T. Ohta, Nat. Commn. 7 (2016) 13814 Aknowledgement This work was supported by JSPS Grant-in-Aid for Scientific Research on Innovative Areas, “Mixed-Anion” (Grant Number JP16H6441).

A high-performance supercapacitor based on N-doped TiO2 nanoparticles

Titanium dioxide (TiO2) is one of the most commercialized metal oxides due to its abundance, low cost, and environmental friendliness. However, its potential for application in electrochemical energy storage devices especially as an electrode material for supercapacitors is limited. In this study, Nitrogen-doped TiO2 (N-doped TiO2) nanoparticles are synthesized through a sol–gel method and their supercapacitive performance is compared with that of TiO2 nanoparticles. X-ray photoelectron spectroscopy (XPS) analysis of N-doped TiO2 proves successful doping of nitrogen into the crystal lattice of the TiO2 nanoparticles with a concentration of 4.1 atom%. Electrochemical properties of the synthesized materials are investigated with a three-electrode system in 3.0 M KCl as the aqueous electrolyte. Electrochemical characterizations proved that nitrogen doping of TiO2 nanoparticles provided an enhanced supercapacitive performance including, specific capacitance of 311 F g−1 at 1 A g−1, 98.9% capacitance retention after 4000 cycles, and a better rate capability than that of bare TiO2 nanoparticles. Results of this study clearly demonstrate that small amount of nitrogen doping into the crystal lattice of TiO2 nanoparticles significantly improves their supercapacitive performance.

Hollow Nitrogen Rich Carbon Nanowire Array Electrode for Application in Lithium-Ion Battery

The anodic aluminum oxide template was prepared and used to fabricate polyacrylonitrile (PAN) nanowire arrays by mechanical hydraulic method, which provides a new idea for the preparation of polymer nanowires. By further carbonize the PAN nanowires at elevated temperatures, the porous nitrogen-rich carbon nanowires could be directly obtained and used as lithium-ion batteries anode material. The nitrogen-rich carbon nanowire based anode exhibited high initial capacities and maintained an outstanding reversible lithium storage capacity of 317.12 mAh g-1 after 50 cycles at a current density of 30 mA g-1, combined with an excellent rate capability of 317.17, 296.70, 265.02, 234.71, 177.02 mAh g-1 under the current density of 30, 50, 100, 200, 500 mA g-1 respectively. Further, this nitrogen-rich carbon nanowire material also has unique advantages in catalysis, supercapacitors and hydrogen storage application potential due to the porous carbon nanowire structure and the large amount of nitrogen doping.

Exploration of the synthesis of three types of multicolor carbon dot originating from isomers.

Currently, the synthesis of carbon dots (CDs) exhibiting long-wavelength emission is still challenging. Herein, we have synthesized for the first time three types of CD with multicolor emission derived from isomers. Importantly, their particle size, nitrogen-doping amount and band gaps collectively regulate the fluorescence emission of the proposed CDs.

Effects of nitrogen doping on surface-enhanced Raman scattering (SERS) performance of bicrystalline TiO 2 nanofibres

Abstract In this work, we successfully synthesized bicrystalline anatase/TiO2(B) nanofibre and used it as active substrate for surface-enhanced Raman scattering (SERS) applications. The bicrystalline structured TiO2 substrates provide additional charge transfer across the anatase-TiO2(B) interface and thus enhanced activity compared to the pure single crystalline phase. With an effort to further increase the sensitivity of SERS, nitrogen element was doped into bicrystalline anatase/TiO2(B) nanofibres (N-TiO2) and higher SERS enhancement was achieved. The nitrogen content was controlled by tuning the calcination temperature of titanate precursor at 500, 600 and 700 °C, respectively. The sample calcined at 600 °C (NT600) acquires the highest percentage of nitrogen element due to its open pore structure that facilitates the diffusion of nitrogen during calcination. Raman intensity depends on the amount of nitrogen doping, thus NT600 exhibited the best SERS activity. The doped nitrogen in TiO2 facilitates the charge transfer between TiO2 and probing molecules and thus suppresses the electron–hole recombination. This work provides a new perspective on the design of efficient TiO2 SERS active substrate and is expected to be valuable for adsorbate detection on semiconductor surface.

A method for adjusting nitrogen doping amount in anatase TiO2 single crystals with well-faceted shape and micron size

A new approach was developed to adjust N doping amount in anatase single crystals with well-faceted shape and micron size, using a novel liquid dopant from the chemical recycling of the wasted supernatant solution in our previous experiments. The dependence of microstructure and property evolution on N doping amount was investigated systematically. The results show that all prepared N-doped samples are pure anatase with the morphology of truncated octahedral bipyramid including both {001} and {110} reactive facets. With the increase of N doping, the single crystals become angular and the thickness decreases, the aggregation of crystals increases, the photo-absorption capacity in visible region is enhanced and the absorption band edge is gradually red-shifted. The photocatalytic efficiency of the samples for the degradation of methylene blue (MB) or phenol under visible light irradiation gradually increases, but when the volume of dopant increases to 2ml, the photoactivity of TiO2 decreases. The optimal volume of N dopant is 1ml and A(6:1) shows the highest photodegradation rate. The effective N doping of wasted supernatant is mainly due to the previously formation of Ti-N linkage, and hence a N doping mechanism is proposed. This work provides a new opportunity for in-situ modification of anatase single crystals with well-faceted shape and micron size, and hence, a basis for development of some advanced materials, for example porous single crystals.

Enhanced Chemoselective Hydrogenation through Tuning the Interaction between Pt Nanoparticles and Carbon Supports: Insights from Identical Location Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy

Ultrasmall-sized platinum nanoparticles (Pt NPs) (∼1 nm) supported on carbon nanotubes (CNTs) with nitrogen doping and oxygen functional groups were synthesized and applied in the catalytic hydrogenation of nitroarenes. The advanced identical location transmission electron microscopy (IL-TEM) method was applied to probe the structure evolution of the Pt/CNT catalysts in the reaction. The results indicate that Pt NPs supported on CNTs with a high amount of nitrogen doping (Pt/H-NCNTs) afford 2-fold activity to that of Pt NPs supported on CNTs with oxygen functional groups (Pt/oCNTs) and 4-fold to that of the commercial Pt NPs supported on active carbon (Pt/C) catalyst toward nitrobenzene. The catalytic performance of Pt/H-NCNTs remained constant during four cycles, whereas the activity of the Pt/oCNTs was halved at the second cycle. Compared with Pt/oCNTs, Pt/H-NCNTs exhibited a higher selectivity (>99%) in chemoselective hydrogenation of halonitrobenzenes to haloanilines due to the electron-rich chemical ...

Spectroscopic Analysis of Nitrogen-Doped Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared By Coaxial Arc Plasma Deposition

Ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) is a new candidate carbon semiconductor applicable to electrical devices. It has been investigated that nitrogen-doping for diamond is ineffective for realizing n-type conduction at room temperature, because nitrogen form a deep donor level of 1.7 eV below the bottom of a conduction band in diamond. For a-C:H, n-type conduction is realized by nitrogen doping, however it is difficult for the carrier density to be controlled widely. On the other hand, it has been reported that nitrogen doping is effective for UNCD/a-C:H prepared by chemical vapor deposition (CVD) and pulsed laser deposition (PLD)1), 2), the doping mechanism for UNCD/a-C:H seems to differ from those for diamond and a-C:H. In this study, UNCD/a-C:H films were prepared by coaxial arc plasma deposition (CAPD) with nitrogen atmosphere and the effects of the nitrogen doping on the UNCD crystallite formation were structurally investigated. X-ray photoemission spectra (XPS), which were measured with MgKα line, of the UNCD/a-C:H films prepared at different inflow ratio of nitrogen and hydrogen (IN/H ). N1s peaks strengthened with an increase in the IN/H , which evidently indicates that the nitrogen content in the film increased with the IN/H . The nitrogen contents of the films deposited at IN/H of 0.25, 0.5, 1.0 and 1.5 were estimated to be 3, 5, 6 and 8 at. %, respectively. Near-edge X-ray absorption fine structure (NEXAFS), spectral shape of the nitrogen-doped films different from the undoped film were obtained. By increasing the doping amount, the intensity of the π*C=N increased, while the intensity of the σ*C-C is decreased. Which refers to strengthen in sp2 bonds and weaken in sp3 bonds. Furthermore, increasing the electrical conductivity by increasing the nitrogen-doping amount can be ascribed to contribute of sp2bonds. The details will be reported at the conference. 1) Dai, et al.: Phys. Rev. B 71, 075421 (2005). 2) T. Yoshitake, et al.: Jpn. J. Appl. Phys 49, 015503 (2010).

Nanostructured carbon-based membranes: nitrogen doping effects on reverse osmosis performance

Ultrathin, flexible and highly water-permeable nanostructured carbon (NC)-based membranes are formed on porous polymer supports by plasma high-power impulse magnetron sputtering in order to fabricate carbon-based membranes for water desalination. The carbon membranes are produced at room temperature using mixtures of argon (Ar), nitrogen (N2) and methane (CH4) as precursors, and this procedure constitutes a simple solvent-free, waste-free scalable process. Structural characterization, molecular simulation, water permeation and salt rejection assessments are used to correlate the performance and membrane structure. Molecular simulations indicate that nitrogen doping on the carbon-based membranes drastically modifies the pore distribution and avoids the formation of clustered regions of high-density carbons. The optimum NC-based membrane has up to 96% salt rejection rate for 0.2 wt% NaCl saline water, with high water permeability ca. 25 l m−2 h−1 MPa−1. The NC-based membranes as active layers for desalination membranes exhibit attractive characteristics which render them a potential alternative to current polymeric technology used in reverse osmosis processes. An ultrathin and flexible carbon-based membrane for desalination can reject up to 96% of salt impurities with high flow rates. Amorphous carbon thin films have a mix of diamond-like and graphite-like chemical bonds that give rise to intriguing applications in semiconductors and designer coatings. Now, Morinobu Endo of Shinshu University in Japan and colleagues has developed a procedure to induce special nanostructure into amorphous carbon membranes for use in water treatment. The team formed sputtered carbon layers by using a mixture of argon, nitrogen and methane gases onto a porous ultrafiltration polymer film using a rapid, high-powered plasma technique. Desalination tests showed that this simple and scalable technique produced robust membranes with high salt rejection rates, particularly when nitrogen dopants were incorporated into the amorphous carbon structure. Nitrogen doping of nanostructured carbon-based membranes allows to produce ultrathin reverse osmosis membranes, which exhibit high robustness for water desalination applications. Structural and chemical characterization, water permeation and salt rejection tests, and computational modeling of these carbon-based membranes is discussed. Their salt rejection performance and degradation resistance reveal a strong dependency on the amount of nitrogen doping within the carbon structure. The properties shown by our nanostructured carbon membranes render them a potential alternative to current polymer-based membranes.

High capacity and high rate capability of nitrogen-doped porous hollow carbon spheres for capacitive deionization

In this work, nitrogen-doped porous hollow carbon spheres (N-PHCS) were well prepared by using polystyrene (PS) spheres as hard templates and dopamine hydrochloride as carbon and nitrogen sources. Field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images demonstrate that the N-PHCS have a uniform, spherical and hollow structure. Nitrogen adsorption–desorption analysis shows that the N-PHCS have a high specific area of 512m2/g. X-ray photoelectron spectroscopy result reveals that the nitrogen doping amount is 2.92%. The hollow and porous structure and effective nitrogen doping can contribute to large accessible surface area, efficient ion transport and good conductivity. In the electrochemical tests, we can conclude that the N-PHCS have a high specific capacitance value, a good stability and low inner resistance. The N-PHCS electrodes present a high salt adsorption capacity of 12.95mg/g at a cell voltage of 1.4V with a flow rate of 40mL/min in a 500mg/L NaCl aqueous solution. Moreover, the N-PHCS electrodes show high salt adsorption rate and good regeneration performance in the CDI process. With high surface specific area and effective nitrogen doping, the N-PHCS is promising to the CDI and other electrochemical applications.

One-step hydrothermal synthesis of nitrogen-doped carbon nanotubes as an efficient electrocatalyst for oxygen reduction reactions.

A high amount of heteroatom doping in carbon, although favorable for enhanced density of catalytically active sites, may lead to substantially decreased electroconductivity, which is necessary for the electrochemical oxygen reduction reaction. Herein, a relatively low amount of nitrogen was successfully doped into carbon nanotubes (CNTs) by a hydrothermal approach in one step, and the synthesized nitrogen-doped CNT (CNT-N) materials retained most of the original, excellent characteristics, such as the graphitic structure, tubular morphology, and high surface area, of CNTs. The resultant CNT-N materials, although containing a relatively low amount of nitrogen doping, exhibited high electrocatalytic ORR activity, comparable to that of 20 wt% Pt/C; long durability; and, more importantly, largely inhibited methanol crossover effect.

Preparation of functionalized water-soluble photoluminescent carbon quantum dots from petroleum coke

Abstract Here we report a new strategy for preparation of water-soluble photoluminescent carbon quantum dots (CQDs) from petroleum coke. Petroleum coke was oxidized first in mixed concentrated H2SO4 and HNO3, and then functionalized by hydrothermal ammonia treatment. The as-made CQDs and nitrogen-doped CQDs (N-CQDs) were characterized by UV–Vis absorption spectroscope, fluorescence spectroscope, transmission electron microscope, atomic force microscope, Raman spectrometer, X-ray powder diffractometer, X-ray photoelectron spectroscope and Fourier transform infrared spectrometer. The results show that the quantum yield of CQDs increases greatly from 8.7 to 15.8%, and the fluorescent lifetime increases from 3.86 to 6.11 ns after the hydrothermal treatment in ammonia. Moreover, the fluorescent color of N-CQDs can be tuned through the amount of doped nitrogen. Both CQDs and N-CQDs are water-soluble, and have uniform particle distribution, strong luminescence, and highly fluorescent sensitivity to pH in a range of 2.0–12.0. The uniform size distribution and nitrogen-doping of N-CQDs help to lead to high yield of radiative recombination, resulting in improved fluorescence properties. This work offers a simple pathway to produce high quality and enhanced photoluminescent CQDs from petroleum coke.

Photodegradation of benzene, toluene and xylenes under visible light applying N-doped mixed TiO2 and ZnO catalysts

N-doped TiO2/ZnO catalysts were prepared by sol–gel technique and calcined at 380 and 500°C. Its photocatalytic activity was evaluated in the photodegradation of benzene, toluene and xylenes (BTX) under visible-LED light and compared with the undoped TiO2/ZnO activity. The amount of doped nitrogen was found to be 0.64at%. Concentrations of BTX were analysed by gas chromatography applying the headspace technique. The NTiO2/ZnO catalyst calcined at 500°C led to reductions of benzene, toluene and xylenes concentrations greater than 80wt% after 120min of irradiation. The photocatalytic reactions followed the first order kinetics.

Control of work function of graphene by plasma assisted nitrogen doping

Nitrogen doping is expected to provide several intriguing properties to graphene. Nitrogen plasma treatment to defect-free and defective highly oriented pyrolytic graphite (HOPG) samples causes doping of nitrogen atom into the graphene layer. Nitrogen atoms are initially doped at a graphitic site (inside the graphene) for the defect-free HOPG, while doping to a pyridinic or a pyrrolic site (edge of the graphene) is dominant for the defective HOPG. The work function of graphene correlates strongly with the site and amount of doped nitrogen. Nitrogen atoms doped at a graphitic site lower the work function, while nitrogen atoms at a pyridinic or a pyrrolic site increase the work function. Control of plasma treatment time and the amount of initial defect could change the work function of graphite from 4.3 eV to 5.4 eV, which would open a way to tailor the nature of graphene for various industrial applications.

Synthesis of Ag/N-TiO2/SBA-15 Photocatalysts and Photocatalytic Reduction of CO2under Visible Light Irradiation

Silver-loaded together with nitrogen-doped highly dispersed TiO2/SBA-15 mesoporous catalysts were success- fully synthesized through solvothermal treatment and calcination method by using titanium n-butoxide (TB), carboxy- late-modified SBA-15 (COOH/SBA-15), urea and silver nitrate as raw materials. The detailed preparation procedure was as follows: 1.0 g COOH/SBA-15 powder was dispersed in solution containing 0.82 mL titanium n-butoxide (TB) and 20.0 mL acetic ether. The mixture was stirred for 30 min at room temperature, then 0.031 g AgNO3 was added into the solution by further stirring for 30 min and a certain amount of urea was added. After being stirred continuously for 3 h, the resultant solu- tion was transferred into a teflon-lined stainless autoclave and solvothermally treated at 220 ℃ for 12 h. After naturally cooling to room temperature, the resultant product was washed three times with absolute ethanol and then dried under vac- uum at 80 ℃ for 12 h. Finally the solids were calcined in air at 550 ℃ for 4 h at a heating rate of 1.5 ℃/min. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), UV-Visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence spectra (PL), inductively coupled plasma atomic emission spectrum (ICP) and elemental analysis (EA). It was revealed that the highly dispersed samples consist of anatase crystalline phase were mesoporous structure. The anatase phase was retained without phase change after silver loading and nitrogen doping. Silver was deposited on the surface of catalysts in the form of metallic silver and served as an effective electron trapper which could prevent the fast recombination of the photo-generated electrons and holes, at the same time, visible light absorption of samples were enhanced by silver nanoparticle based on its surface plasmon resonance effect. Nitrogen was doped into TiO2 matrix in the form of both interstitial nitrogen and substitu- tional nitrogen, nitrogen dopants might be presented in the chemical environment of Ti-O-N and O-Ti-N. On one hand, nitro- gen doping could extend the adsorption of catalysts to the visible light region (λ>400 nm); on the other hand, appropriate amount of nitrogen doping could inhibit the recombination of the photo-generated charge carriers and increase the efficiency of the photocurrent carriers. The high photocatalytic performance could be attributed to the synergistic effect of nitrogen doping and the loaded silver nanoparticles over TiO2. The nitrogen doping concentration had an optimal value. When the loading amount of Ag was 2 wt% and the theoretical mole ratio of nitrogen to Ti was 3, the photocatalyst had the highest photocatalytic activity. The methanol yield was 45.7 μmolg -1 •h -1 .

Plasma synthesis of nitrogen-doped porous graphene supporting Pd nanoparticles as a new catalyst for C–C coupling reactions

We report an environmentally-friendly approach to the synthesis of hybrids based on porous graphene and metal nanoparticles. The nitrogen-doped porous graphene (N-PG) and Pd nanoparticles decorated N-PG (Pd/N-PG) was synthesized by a plasma method. The N-PG was characterized by X-ray photoelectron spectroscopy and Raman spectroscopy, and the results clearly indicate that the amount of nitrogen doping was 6.65 wt%. The synthesized Pd/N-PG hybrid materials were confirmed by transmission electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy mapping. The hybrid material based on Pd/N-PG as a new catalyst was applied in Suzuki reaction. This catalyst offers a number of advantages such as high stability, easy removal from the reaction mixture and reusability with minimal loss of activity, showing better performance than the well-known commercial Pd/C catalyst.

Charge‐Transport Tuning of Solution‐Processable Graphene Nanoribbons by Substitutional Nitrogen Doping

Novel nitrogen‐doped graphene nanoribbons (GNR‐Ns) are synthesized by the coupling reaction between a pyrazine (or benzene) derivative and naphthalene followed by cyclodehydrogenation. The amount of nitrogen doping in the GNR‐Ns is controlled by changing the monomer feed ratio of pyrazine to benzene for polymerization. The electron mobility of the GNR‐Ns increases while the hole mobility decreases, as the amount of nitrogen doping in the GNR increases, indicating that the charge‐transport behavior of GNRs is changed from ambipolar to an n‐type semiconductor. The threshold voltage of the GNR‐Ns also shifts from 20 to −6 V as the amount of nitrogen doping increases. image