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Markus Antonietti - One of the best experts on this subject based on the ideXlab platform.

  • boron Carbon Nitride thin films from disordered to ordered conjugated ternary materials
    Journal of the American Chemical Society, 2020
    Co-Authors: Paolo Giusto, Daniel Cruz, Tobias Heil, Hiroki Arazoe, Paola Lova, Takuzo Aida, Markus Antonietti
    Abstract:

    We present an innovative method for the synthesis of boron Carbon Nitride thin film materials in a simple furnace setup, using commonly available solid precursors and relatively low temperature compared to previous attempts. The as-prepared structural and optical properties of thin films are tuned via the precursor content, leading to a sp2-conjugated boron Nitride-Carbon Nitride mixed material, instead of the commonly reported boron Nitride-graphene phase segregation, with tunable optical properties such as band gap and fluorescence.

  • influence of thiazole modified Carbon Nitride nanosheets with feasible electronic properties on inverted perovskite solar cells
    Journal of the American Chemical Society, 2019
    Co-Authors: Daniel Cruz, Baris Kumru, Bernhard V K J Schmidt, Jose Garcia Cerrillo, Jose Dario Perea, Iver Lauermann, Christoph J Brabec, Markus Antonietti
    Abstract:

    Effective, solution-processable designs of interfacial electron-transporting layers (ETLs) or hole-blocking layers are promising tools in modern electronic devices, e.g., to improve the performance, cost, and stability of perovskite-based solar cells. Herein, we introduce a facile synthetic route of thiazole-modified Carbon Nitride with 1.5 nm thick nanosheets which can be processed to a homogeneous, metal-free ETL for inverted perovskite solar cells. We show that thiazole-modified Carbon Nitride enables electronic interface enhancement via suppression of charge recombination, achieving 1.09 V in Voc and a rise to 20.17 mA/cm2 in Jsc. Hence, this report presents the successful implementation of a Carbon-Nitride-based structure to boost charge extraction from the perovskite absorber toward the electron transport layer in p-i-n devices.

  • electrostatic stabilization of Carbon Nitride colloids in organic solvents enables stable dispersions and transparent homogeneous cn films for optoelectronics
    Journal of the American Chemical Society, 2018
    Co-Authors: Baris Kumru, Bernhard V K J Schmidt, Daniel Cruz, Tobias Heil, Markus Antonietti
    Abstract:

    Covalent modification of phenyl-modified Carbon Nitride with vinylthiazole groups via visible light induced grafting is reported. Modified structures express negative charge migration to the thiazole edges while the Carbon Nitride sheet remains positively charged in organic solutions. Such a phenomenon provides electrostatic stabilization of modified Carbon Nitride particles in organic media leading to highly organodispersible and colloidally stable Carbon Nitrides. The resulting structures can be homogeneously dispersed in organic solvents and can be cast to transparent films. The usefulness of such a processable colloidal Carbon Nitride building block is exemplified here by its high luminescence and inkjet printing of films.

  • Graphitic Carbon Nitride “Reloaded” Emerging Applications Beyond (Photo)Catalysis
    ChemInform, 2016
    Co-Authors: Jian Liu, Hongqiang Wang, Markus Antonietti
    Abstract:

    Review: renaissance of graphitic Carbon Nitride (g-C3N4) as a highly active photo/electrocatalyst, and diverse applications of the metal-free polymer; 94 refs.

  • phenyl modified Carbon Nitride quantum dots with distinct photoluminescence behavior
    Science & Engineering Faculty, 2016
    Co-Authors: Qianling Cui, Markus Antonietti, Xiaoyu Wang, Menny Shalom
    Abstract:

    A novel type of quantum dot (Ph-CN) is manufactured from graphitic Carbon Nitride by “lining” the Carbon Nitride structure with phenyl groups through supramolecular preorganization. This approach requires no chemical etching or hydrothermal treatments like other competing nanoparticle syntheses and is easy and safe to use. The Ph-CN nanoparticles exhibit bright, tunable fluorescence, with a high quantum yield of 48.4 % in aqueous colloidal suspensions. Interestingly, the observed Stokes shift of approximately 200 nm is higher than the maximum values reported for Carbon Nitride based fluorophores. The high quantum yield and the large Stokes shift are related to the structural surface organization of the phenyl groups, which affects the π-electron delocalization in the conjugated Carbon Nitride networks and induces colloidal stability. The remarkable performance of the Ph-CN nanoparticles in imaging is demonstrated by a simple incubation study with HeLa cells.

Xinchen Wang - One of the best experts on this subject based on the ideXlab platform.

  • Functional Carbon Nitride materials design strategies for electrochemical devices
    Nature Reviews Materials, 2017
    Co-Authors: Fabian K. Kessler, Xinchen Wang, Yun Zheng, Dana Schwarz, Christoph Merschjann, Wolfgang Schnick, Michael J. Bojdys
    Abstract:

    In the past decade, research in the field of artificial photosynthesis has shifted from simple, inorganic semiconductors to more abundant, polymeric materials. For example, polymeric Carbon Nitrides have emerged as promising materials for metal-free semiconductors and metal-free photocatalysts. Polymeric Carbon Nitride (melon) and related Carbon Nitride materials are desirable alternatives to industrially used catalysts because they are easily synthesized from abundant and inexpensive starting materials. Furthermore, these materials are chemically benign because they do not contain heavy metal ions, thereby facilitating handling and disposal. In this Review, we discuss the building blocks of Carbon Nitride materials and examine how strategies in synthesis, templating and post-processing translate from the molecular level to macroscopic properties, such as optical and electronic bandgap. Applications of Carbon Nitride materials in bulk heterojunctions, laser-patterned memory devices and energy storage devices indicate that photocatalytic overall water splitting on an industrial scale may be realized in the near future and reveal a new avenue of ‘post-silicon electronics’. Carbon Nitrides are potentially cheap and metal-free alternatives for catalysts, semiconductors, battery materials and memory devices. In this Review, we discuss the synthesis, design and morphology of these materials, and reflect on the ability of methods such as templating, etching, dye sensitization, heteroatom doping and co-polymerization, as well as the assembly of various heterojunctions, to improve device performance.

  • sulfur doped Carbon Nitride polymers for photocatalytic degradation of organic pollutant and reduction of cr vi
    Molecules, 2017
    Co-Authors: Yun Zheng, Feng Lin, Fangsong Guo, Khalid A Alamry, Layla A Taib, Abdullah M Asiri, Xinchen Wang
    Abstract:

    As a promising conjugated polymer, binary Carbon Nitride has attracted extensive attention as a metal-free and visible-light-responsive photocatalyst in the area of photon-involving purification of water and air. Herein, we report sulfur-doped polymeric Carbon Nitride microrods that are synthesized through thermal polymerization based on trithiocyanuric acid and melamine (TM) supramolecular aggregates. By tuning the polymerization temperature, a series of sulfur-doped Carbon Nitride microrods are prepared. The degradation of Rhodamine B (RhB) and the reduction of hexavalent chromium Cr(VI) are selected as probe reactions to evaluate the photocatalytic activities. Results show that increasing pyrolysis temperature leads to a large specific surface area, strong visible-light absorption, and accelerated electron-hole separation. Compared to bulk Carbon Nitride, the highly porous sulfur-doped Carbon Nitride microrods fabricated at 650 °C exhibit remarkably higher photocatalytic activity for degradation of RhB and reduction of Cr(VI). This work highlights the importance of self-assembly approach and temperature-control strategy in the synthesis of photoactive materials for environmental remediation.

  • photocatalytic reduction of co2 by graphitic Carbon Nitride polymers derived from urea and barbituric acid
    Applied Catalysis B-environmental, 2015
    Co-Authors: Jiani Qin, Sibo Wang, He Ren, Yidong Hou, Xinchen Wang
    Abstract:

    Abstract Conjugated Carbon Nitride nanosheets modified with barbituric acid (BA) were synthesized by a facile one-pot chemical condensation of urea. The obtained BA-modified Carbon Nitride samples were termed as CNU-BA X and were fully characterized by XRD, FTIR, XPS, NMR, EPR, FESEM, TEM, DRS, PL, BET and photocurrent measurements. The performance of the developed Carbon Nitride based semiconductors was investigated by applying them as polymeric photocatalysts for the reduction of CO 2 under visible light illumination. Results revealed that the copolymerization of urea with BA co-monomer strongly alternated the physical and chemical properties of Carbon Nitride polymer by improving optical absorption and creating surface molecular heterojunction that promoted charge separation, and consequently the enhanced photocatalytic performance was achieved. Various reaction parameters were investigated and optimized for the reaction system, and we found that under the optimal reaction condition, the best sample (CNU-BA 0.03 ) could effectively photocatalyze the CO 2 -to-CO conversion reaction with 15-fold-enhanced catalytic activity, compared to the non-modified sample derived from urea (named as CNU). Other typical comonomers were also selected to polymerize with urea to study the beneficial effect of copolymerization on the development of efficient Carbon Nitride based nanostructures for CO 2 photoreduction.

  • mesoporous Carbon Nitride tungsten oxide composites for enhanced photocatalytic hydrogen evolution
    Chemsuschem, 2015
    Co-Authors: Kamalakannan Kailasam, Anna Fischer, Michael Schwarze, Guigang Zhang, Xinchen Wang, Marc Schröder, Jinshui Zhang, Arne Thomas
    Abstract:

    Composites of mesoporous polymeric Carbon Nitride and tungsten(VI) oxide show very high photocatalytic activity for the evolution of hydrogen from water under visible light and in the presence of sacrificial electron donors. Already addition of very small amounts of WO3 yields up to a twofold increase in the efficiency when compared to bulk Carbon Nitrides and their composites and more notably even to the best reported mesoporous Carbon Nitride-based photocatalytic materials. The higher activity can be attributed to the high surface area and synergetic effect of the Carbon Nitrides and the WO3 resulting in improved charge separation through a photocatalytic solid-state Z-scheme mechanism.

  • the effect of the pore wall structure of Carbon Nitride on photocatalytic co2 reduction under visible light
    Journal of Materials Chemistry, 2014
    Co-Authors: Kazuhiko Maeda, Xinchen Wang, Mingwen Zhang, Ryo Kuriki, Osamu Ishitani
    Abstract:

    Carbon Nitride (C3N4) polymers work as a vital component in a photocatalytic CO2 reduction assembly that operates under visible light when modified with a ruthenium complex, trans(Cl)-[Ru{4,4′-(CH2PO3H2)2-2,2′-bipyridine}(CO)2Cl2], (Ru) as a catalyst. Here we examined the effects of structural properties of Carbon Nitride on the photocatalytic performance for CO2 reduction into formic acid. Introduction of mesoporosity into the graphitic Carbon Nitride structure increased the specific surface area, leading to significant enhancement in activity. However, higher surface area (in other words, lower crystallinity) that originated from excessively introduced mesopores had a negative impact on activity, although it is a prerequisite to allow for adsorption of Ru on the Carbon Nitride surface. Thus, the activity was sensitive to specific surface area and crystallinity of Carbon Nitride, but is largely insensitive to the pore size and the volume.

Jürgen P. Rabe - One of the best experts on this subject based on the ideXlab platform.

  • triazine based graphitic Carbon Nitride a two dimensional semiconductor
    Angewandte Chemie, 2014
    Co-Authors: Gerardo Algarasiller, Markus Antonietti, Nikolai Severin, Samantha Y. Chong, Torbjörn Björkman, Robert G. Palgrave, Andrea Laybourn, Yaroslav Z. Khimyak, Arkady V. Krasheninnikov, Jürgen P. Rabe
    Abstract:

    Graphitic Carbon Nitride has been predicted to be structurally analogous to Carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic Carbon Nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes.

  • Triazine‐Based Graphitic Carbon Nitride: a Two‐Dimensional Semiconductor
    Angewandte Chemie (International ed. in English), 2014
    Co-Authors: Gerardo Algara-siller, Markus Antonietti, Nikolai Severin, Samantha Y. Chong, Torbjörn Björkman, Robert G. Palgrave, Andrea Laybourn, Yaroslav Z. Khimyak, Arkady V. Krasheninnikov, Jürgen P. Rabe
    Abstract:

    Graphitic Carbon Nitride has been predicted to be structurally analogous to Carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic Carbon Nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes.

Koji Kato - One of the best experts on this subject based on the ideXlab platform.

  • Nano-Scale Fatigue Wear of Carbon Nitride Coatings: Part I—Wear Properties
    Journal of Tribology, 2003
    Co-Authors: Dong F. Wang, Koji Kato
    Abstract:

    This paper, the first of two companion papers, reports empirical data on wear properties in Carbon Nitride coatings by a spherical diamond counter-face in repeated sliding contacts through in situ examination and post-sliding observation, with an emphasis on the effects of friction cycles and normal load. In the repeated sliding, a specific wear amount of about 10 -9 mm 3 /Nm was observed on the wear track of the Carbon Nitride coating when no wear particles were detected. On the other hand, a specific wear amount of about 10 -6 mm 3 /Nm was observed on the wear track of the Carbon Nitride coating, where wear particles were generated after a certain number of friction cycles. Wear rate change corresponds to a wear mode change. From in situ examination, the critical number of friction cycles, Nc, for wear particle generation is proven to be related to a wear mode change.

  • Effect of friction cycles on wear particle generation of Carbon Nitride coating against a spherical diamond
    Tribology International, 2000
    Co-Authors: Dong F. Wang, Koji Kato
    Abstract:

    Abstract The in-situ observations of wear particle generation of Carbon Nitride coating on silicon repeatedly sliding against a spherical diamond have been studied in terms of the critical friction cycles and normal loads. An environmental scanning electron microscope (E-SEM), in which a pin-on-disk tribotester was installed, has in-situ provided direct evidence of when and how the wear particle generation do occur during the repeated sliding of Carbon Nitride coating against a spherical diamond. The in-situ observations of non-conductive Carbon Nitride coating are therefore available free from surface charging with controllable relative humidity. The repeated sliding tests at a sliding speed of 50 μm/s have been carried out with the purpose of observing the ‘No wear particle generation’ region when varying normal load from 10 to 250 mN. It appears that until 20 friction cycles, the maximum Hertzian contact pressure P max for ‘No wear particle generation’ can be improved from 1.39 Y to 1.53 Y if silicon is coated by Carbon Nitride with a thickness of 10 nm, where Y is defined as the yield strength of silicon. The applicable enlargement of the ‘No wear particle generation’ region of Carbon Nitride coating has therefore been comparatively discussed with the silicon substrate from the view points of the friction coefficient and the specific wear rate. The mode transition maps have also been summarized for the repeated sliding of Carbon Nitride coating in terms of ‘No wear particle generation’, ‘Wear particle generation by microcutting’ and ‘Wear particle generation by microcutting and microfracturing’ three typical modes.

Jinshui Zhang - One of the best experts on this subject based on the ideXlab platform.

  • mesoporous Carbon Nitride tungsten oxide composites for enhanced photocatalytic hydrogen evolution
    Chemsuschem, 2015
    Co-Authors: Kamalakannan Kailasam, Anna Fischer, Michael Schwarze, Guigang Zhang, Xinchen Wang, Marc Schröder, Jinshui Zhang, Arne Thomas
    Abstract:

    Composites of mesoporous polymeric Carbon Nitride and tungsten(VI) oxide show very high photocatalytic activity for the evolution of hydrogen from water under visible light and in the presence of sacrificial electron donors. Already addition of very small amounts of WO3 yields up to a twofold increase in the efficiency when compared to bulk Carbon Nitrides and their composites and more notably even to the best reported mesoporous Carbon Nitride-based photocatalytic materials. The higher activity can be attributed to the high surface area and synergetic effect of the Carbon Nitrides and the WO3 resulting in improved charge separation through a photocatalytic solid-state Z-scheme mechanism.

  • exfoliated graphitic Carbon Nitride nanosheets as efficient catalysts for hydrogen evolution under visible light
    Advanced Materials, 2013
    Co-Authors: Shubin Yang, Xinchen Wang, Jinshui Zhang, Yongji Gong, Liang Zhan, Zheyu Fang, Robert Vajtai, Pulickel M Ajayan
    Abstract:

    Graphitic Carbon Nitride nanosheets are extracted, produced via simple liquid-phase exfoliation of a layered bulk material, g-C3N4. The resulting nanosheets, having ≈2 nm thickness and N/C atomic ratio of 1.31, show an optical bandgap of 2.65 eV. The Carbon Nitride nanosheets are demonstrated to exhibit excellent photocatalytic activity for hydrogen evolution under visible light.

  • synthesis of Carbon Nitride semiconductors in sulfur flux for water photoredox catalysis
    ACS Catalysis, 2012
    Co-Authors: Jinshui Zhang, Guigang Zhang, Mingwen Zhang, Xinchen Wang
    Abstract:

    Sulfur-mediated synthesis has been demonstrated as a simple but efficient pathway to control the texture and electronic structure of poly(tris-triazine) based graphitic Carbon Nitride semiconductors with improved photocatalytic reactivity over the pristine counterpart. Here, we advance this strategy by employing cheap and easily available elemental sulfur as the external sulfur species instead of sulfur-containing precursors for the sulfur-mediated synthesis of polymeric Carbon Nitride photocatalysts. Characterization results revealed that the multiple thermal condensations of Carbon Nitride precursors in the hot sulfur flux provided a facile means to promote the formation of graphitic-like Carbon Nitride conjugated systems, altering the traditional route of thermal-induced self-polymerization of melamine. The textural, electronic, and optical properties of the resultants organic semiconductors was therefore strongly modified to endow the materials with improved physical and chemical properties, as demons...

  • polycondensation of thiourea into Carbon Nitride semiconductors as visible light photocatalysts
    Journal of Materials Chemistry, 2012
    Co-Authors: Guigang Zhang, Jinshui Zhang, Mingwen Zhang, Xinchen Wang
    Abstract:

    Converting solar energy into hydrogen gas by water splitting is considered as a long-term solution to address global energy and environmental problems. Great effort has been devoted to the search for abundant systems for the purpose of efficient capture, conversion, and storage of solar energy in a cost-effective manner. To further advance the recently-developed Carbon Nitride photocatalysis for solar hydrogen generation, thiourea, a sulfur-containing compound, was used as a cheap and easily-available starting material for the synthesis of graphitic Carbon Nitride semiconductors. The as-prepared photocatalysts were subjected to several characterizations, and the results showed that the heating temperature and the presence of sulfur motifs offer a facile chemical pathway for the control of the condensation/polymerization of Carbon Nitride, and thus adjusting their textural and electronic properties. Photocatalytic activity experiments demonstrated that the g-C3N4 synthesized from thiourea exhibited a much higher H2 production rate than that of g-C3N4 prepared from dicyanamide or urea, and this activity can be further enhanced by increasing the condensation temperature.