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

  • hydrogen reduction treatment of boron Carbon Nitrides for photocatalytic selective oxidation of alcohols
    Applied Catalysis B-environmental, 2020
    Co-Authors: Min Zhou, Pengju Yang, Zheng Chen, Sibo Wang, Caijin Huang, Xinchen Wang
    Abstract:

    Abstract Light-driven selective oxidation of aromatic alcohols allows a sustainable and eco-friendly manner to convert solar energy into highly valuable aromatic aldehydes. However, the low separation and transfer efficiency of photogenerated charge carriers and the sluggish reaction kinetics seriously restrict the efficiency of the organic photosynthesis of desired compounds. Herein, a facile strategy is adopted to regulate the boron Carbon Nitrides (BCN) semiconductors by hydrogen reduction to precisely tune the structural and surface properties. The reduced BCN materials can effectively enhance charge separation and migration as well as promote O2 activation and mass transfers. As a result, this BCN catalyst therefore displays a remarkable enhancement in photosynthesis of aromatic aldehydes from the alcohols with high conversion and selectivity compared to pristine BCN.

  • cobalt based cubane molecular co catalysts for photocatalytic water oxidation by polymeric Carbon Nitrides
    Applied Catalysis B-environmental, 2018
    Co-Authors: Zhishan Luo, Min Zhou, Xinchen Wang
    Abstract:

    Abstract In artificial photocatalysis, sluggish kinetics of hole transfer and the high recombination rate of charge have been the Achilles’ heel of photocatalytic conversion efficiency. The development of co-catalysts for promoting exciton splitting and charge separation has therefore gained continuous attention. Herein, “Co4O4” cubane complex Co4O4(O2CMe)4(py)4 (1a, py = pyridine derivatives), serves as a homogeneous molecular co-catalyst which is engineered into the framework of pristine polymeric Carbon nitride (PCN) for water oxidation with light illumination. This modification strategy maximizes the contact areas between co-catalysts and reactants, reduces the over-potential of oxygen producing and accelerates the interface transfer rate of electron-hole pairs, thus leading to enhanced reaction kinetics for photocatalytic water oxidation. Compared with pristine PCN, the photocatalytic O2 production rate up to 19-fold-enhanced in the presence of molecular co-catalyst. This work emphasizes the importance of developing effective, stable and earth-abundant molecular co-catalysts for the promotion of water-splitting photocatalysis.

  • photocatalytic co2 conversion by polymeric Carbon Nitrides
    Chemical Communications, 2018
    Co-Authors: Yuanxing Fang, Xinchen Wang
    Abstract:

    CO2 is a vital compond for life, and its concentration significantly affects the living environment of the Earth. Extensive effort has been devoted to balance its concentration. Among the developed approaches, photocatalytic CO2 conversion is considered as an ideal option. Previous reports suggest polymeric Carbon nitride (PCN) can be effectively used as a metal-free photocatalyst to convert CO2. Herein, the recent developments of PCN and the related photocatalysts for CO2 conversion are summarized from the fundamental of using PCN, and their extended applications through molecular modification and physical/chemical coupling with other substances. The concluding remarks finally indicate the future challenges of using PCN materials for relevant solar-driven applications.

  • visible light responsive photocatalysts from tio2 to Carbon Nitrides and boron Carbon nitride
    2018
    Co-Authors: Bo Wang, Masakazu Anpo, Xinchen Wang
    Abstract:

    Abstract It can be said that energy depletion and environmental pollution on a global scale are the most serious and urgent issues facing mankind in recent times. It is, thus, vital to design novel energy production and conversion systems that utilize natural energy and allow sustainable development without environmental destruction or pollution. In line with these objectives, the decomposition of H2O into H2 and O2, as well as the related reactions using visible light-responsive photocatalysts under sunlight irradiation, has been intensively investigated as one of the most promising environmentally benign energy production systems to address these issues. In the past half century, research on various photocatalytic systems using metal oxides has been carried out. However, to achieve higher efficiency in the production of H2, more innovative breakthroughs in the development of photocatalytic materials are strongly desired. To address such issues, graphitic Carbon nitride (g-C3N4) and hexagonal boron Carbon nitride (BCN) nano-materials have been investigated as promising visible light-responsive photocatalytic materials. In this chapter, we have highlighted the development of such g-C3N4 and hexagonal BCN photocatalytic nano-materials, focusing on their design, construction and optimization, as well as their applications to environmentally benign solar energy conversion systems, for the decomposition of H2O, reduction and fixation of CO2, and organic redox reactions. Such visible light-responsive photocatalytic materials are considered to be the most important research for the development of safe and clean energy production technologies for the 21st century and beyond.

  • tri s triazine based crystalline Carbon nitride nanosheets for an improved hydrogen evolution
    Advanced Materials, 2017
    Co-Authors: Lihua Lin, Yun Zheng, Pengju Yang, Yuanxing Fang, Xinchen Wang
    Abstract:

    Tri-s-triazine-based crystalline Carbon nitride nanosheets (CCNNSs) have been successfully extracted via a conventional and cost-effective sonication–centrifugation process. These CCNNSs possess a highly defined and unambiguous structure with minimal thickness, large aspect ratios, homogeneous tri-s-triazine-based units, and high crystallinity. These tri-s-triazine-based CCNNSs show significantly enhanced photocatalytic hydrogen generation activity under visible light than g-C3N4, poly (triazine imide)/Li+ Cl–, and bulk tri-s-triazine-based crystalline Carbon Nitrides. A highly apparent quantum efficiency of 8.57% at 420 nm for hydrogen production from aqueous methanol feedstock can be achieved from tri-s-triazine-based CCNNSs, exceeding most of the reported Carbon nitride nanosheets. Benefiting from the inherent structure of 2D crystals, the ultrathin tri-s-triazine-based CCNNSs provide a broad range of application prospects in the fields of bioimaging, and energy storage and conversion.

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

  • photoredox catalytic organic transformations using heterogeneous Carbon Nitrides
    Angewandte Chemie, 2018
    Co-Authors: Aleksandr Savateev, Indrajit Ghosh, Burkhard Konig, Markus Antonietti
    Abstract:

    : Photoredox catalysis comprising homogeneous transition-metal-based systems, organic dyes, and semiconductors, has become a universal tool to catalyze a wide variety of chemical reactions with high selectivity and under mild conditions using visible light irradiation. This Minireview summarizes recent progress in photoredox catalysis mediated by heterogeneous Carbon nitride materials such as mesoporous graphitic Carbon nitride (mpg-CN), polymeric Carbon nitride, and potassium poly(heptazine imides) (K-PHI). Because of the high thermal, chemical, and photostability of these materials, as well as favorable conduction and valence band positions, Carbon Nitrides expand the reaction range of photocatalysis to many novel reactions, such as photocatalytic activation of elemental sulfur to furnish a convenient chemical route to organosulfur compounds.

  • 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.

  • heterogeneous organocatalysis for photoredox chemistry
    ACS Catalysis, 2018
    Co-Authors: Aleksandr Savateev, Markus Antonietti
    Abstract:

    Photoredox catalysis is a tool enabling a wide variety of chemical reactions with high selectivity under mild conditions of visible light. In this Review, we summarize recent experiments which use heterogeneous, covalent, metal-free semiconductors with adjustable reactivity to drive such reactions. This class started with mesoporous graphitic Carbon nitride, then continued with poly(heptazine imides), but is meanwhile extended to other polymers and solid-state organics with conjugated electron system. Because of the high thermal and chemical stability, as well as adjustable conduction and valence band positions, the reaction space could be expanded to many organic reactions, such as photocatalytic synthesis of organosulfur compounds, or unconventional halogenation and cyanation reactions. Performance of Carbon Nitrides and homogeneous systems in certain reactions was compared in the present Review.

  • photooxidation of n acylhydrazones to 1 3 4 oxadiazoles catalyzed by heterogeneous visible light active Carbon nitride semiconductor
    Applied Catalysis B-environmental, 2018
    Co-Authors: Bogdan Kurpil, Markus Antonietti, Katharina Otte, Aleksandr Savateev
    Abstract:

    Abstract The remarkable bioactivity of 1,3,4-oxadiazoles permanently motivates chemists to develop new milder and broader approaches to synthesize new derivatives, as well as to improve the preparation methodologies of the known compounds. Potassium poly(heptazine imide), a well crystallized representative of Carbon Nitrides family, shows great performance as a heterogeneous and hence recyclable photocatalyst in the visible light driven oxidative cyclization of N-acylhydrazones to the corresponding oxadiazoles. The proposed method uses elemental sulfur as a cheap and selective electron scavenger. A series of 2,5-disubstituted-1,3,4-oxadiazoles bearing aryl, hetaryl and alkyl substituents were obtained with 42–84% isolated yield.

  • triazoles a new class of precursors for the synthesis of negatively charged Carbon nitride derivatives
    Chemistry of Materials, 2015
    Co-Authors: Dariya Dontsova, Zupeng Chen, Sergey Pronkin, Marko Wehle, Christian Fettkenhauer, Guylhaine Clavel, Markus Antonietti
    Abstract:

    Carbon nitride polymers were prepared for the first time by the pyrolysis of 3,5-disubstituted-1,2,4-triazole derivatives, namely, 3,5-diamino-1,2,4-triazole [1] and 3-amino-1,2,4-triazole-5-thiol [2], in bulk as well as in LiCl/KCl salt melts. The reaction of [1] and [2] in bulk yields condensed heptazine-based polymers, while in LiCl/KCl eutectics it leads to the formation of well-defined potassium poly(heptazine imides), according to the results of 13C NMR and XPS investigations, whose formation resembles that of emeraldine salts of polyaniline. The density functional calculations supported the structural model suggested for potassium poly(heptazine imide) polymer. Owing to the specific reaction path, the products obtained from triazoles therefore show electronic properties rather different to known Carbon Nitrides, such as band gap and conduction and valence bands positions. With the degree of crystallinity of the reference materials, triazole-derived Carbon Nitrides are characterized by almost comple...

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

  • coupled fluorometer potentiostat system and metal free monochromatic luminophores for high resolution wavelength resolved electrochemiluminescent multiplex bioassay
    ACS Sensors, 2018
    Co-Authors: Zhixin Zhou, Yanfei Shen, Qing Zhou, Songqin Liu, Yuanjian Zhang
    Abstract:

    The sensitive simultaneous detection of multiple biomarkers is critical for the early diagnosis of diseases. Electrochemiluminescence (ECL) offers outstanding advantages, e.g., low background, over other optical sensing techniques. However, multiplexed ECL bioassay is hindered not only by the lack of generally available ECL spectrometers but also by the limited number of biocompatible monochromatic ECL luminophores for decades. Herein, we report addressing these issues by re-examination of the recent tabletop spectrofluorometer coupled potentiostat as a high-resolution ECL spectrum acquisition system and using Carbon Nitrides as monochromatic luminophores. A wavelength-resolved multiplexing ECL biosensor is demonstrated to simultaneously detect CA19-9 and mesothelin, two pancreatic cancer biomarkers, at a single-electrode interface. This work could initiate new opportunities for more general multiplex ECL biosensors with competitive performances.

  • Coupled Fluorometer-Potentiostat System and Metal-Free Monochromatic Luminophores for High-Resolution Wavelength-Resolved Electrochemiluminescent Multiplex Bioassay
    2018
    Co-Authors: Zhixin Zhou, Yanfei Shen, Qing Zhou, Songqin Liu, Yuanjian Zhang
    Abstract:

    The sensitive simultaneous detection of multiple biomarkers is critical for the early diagnosis of diseases. Electrochemiluminescence (ECL) offers outstanding advantages, e.g., low background, over other optical sensing techniques. However, multiplexed ECL bioassay is hindered not only by the lack of generally available ECL spectrometers but also by the limited number of biocompatible monochromatic ECL luminophores for decades. Herein, we report addressing these issues by re-examination of the recent tabletop spectrofluorometer coupled potentiostat as a high-resolution ECL spectrum acquisition system and using Carbon Nitrides as monochromatic luminophores. A wavelength-resolved multiplexing ECL biosensor is demonstrated to simultaneously detect CA19-9 and mesothelin, two pancreatic cancer biomarkers, at a single-electrode interface. This work could initiate new opportunities for more general multiplex ECL biosensors with competitive performances

  • facile one pot synthesis of nanoporous Carbon nitride solids by using soft templates
    Chemsuschem, 2010
    Co-Authors: Yong Wang, Xinchen Wang, Markus Antonietti, Yuanjian Zhang
    Abstract:

    Carbon materials have attracted much attention because they are attractive for a wide range of applications, and also because of the scientific interest in the challenges posed by their synthesis, processing, and characterization. Recently, Carbon materials with various morphologies and contain heteroatoms such as nitrogen and boron have been actively pursued and considered as the most promising candidates to complement Carbon in materials applications. For example, graphitic Carbon nitride (g-C3N4) is a potentially useful substitute for amorphous and graphitic Carbon in a variety of applications, such as catalytic supports and gas storage. Because there are many ways to substitute Carbon by nitrogen in graphite in a regular fashion, here the term Carbon Nitrides is understood to comprise a large family of related compounds (e.g. , C3N4, C3N2, C3N, C5N, C10N3, and others). Accordingly, various strategies have been adopted to prepare the nitrogen-enriched Carbon materials. Many groups have succeeded in synthesizing graphitic Carbon Nitrides via condensation of C-, N-, and H-containing precursors. For example, Kawaguchi synthesized a graphitic hexagonal polymer, (C3N3)2(NH)3, which was found to be stable up to 500 8C. Through a solid-state reaction of 2,4,6-triamino1,3,5-triazine with 2,4,6-trichloro-1,3,5-triazine in a high pressure-high temperature condition, Wolf et al. obtained a wellcharacterized and highly crystalline graphitic Carbon nitride derivative. The generated HCl played the role of a template by filling the nitridic in-plane pores of a triazine-based condensation pattern. Gao et al. were able to prepare Carbon nitride at atmospheric pressure from polymerized (CH2NH2)2 and CCl4. [7]

Arne Thomas - 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.

  • three dimensional macroscopic assemblies of low dimensional Carbon Nitrides for enhanced hydrogen evolution
    Angewandte Chemie, 2013
    Co-Authors: Youngsi Jun, Arne Thomas, Won Hi Hong, Jihee Park, Sun Uk Lee, Galen D Stucky
    Abstract:

    Simple organic cooperative assembly of triazine molecules leads to three-dimensional macroscopic assemblies of low-dimensional graphitic Carbon Nitrides (g-CNs), for example, nanoparticles, nanotubes, and nanosheets. The approach enables the characterization of the cooperative properties and photocatalytic activities of low-dimensional g-CN materials in hydrogen evolution reactions from water under visible light.

  • three dimensional macroscopic assemblies of low dimensional Carbon Nitrides for enhanced hydrogen evolution
    Angewandte Chemie, 2013
    Co-Authors: Jihee Park, Arne Thomas, Won Hi Hong, Galen D Stucky
    Abstract:

    Nanomaterials feature unique surface, optical, and electronicproperties that are often superior to their bulk counterparts.These properties are often interpreted as surface effect anddimensional confinement, which forms the basis to design thenanoscale building blocks or devices for catalysis, electronics,or optics.

  • mesoporous Carbon nitride silica composites by a combined sol gel thermal condensation approach and their application as photocatalysts
    Energy and Environmental Science, 2011
    Co-Authors: Kamalakannan Kailasam, Arne Thomas, Jan Dirk Epping, Sebastian Losse, Henrik Junge
    Abstract:

    Mesoporous Carbon Nitrides, silicas and their composites have been prepared by a combined sol–gel and thermal condensation approach. Precursors for the Carbon nitride (cyanamide) and silica (TEOS) are mixed and condensed simultaneously. After condensation and heat treatment it is observed that the Carbon nitride and silica formed highly interpenetrating mesophases which leads either to the formation of mesoporous Carbon nitride or silica after selective removal of one of the phases. Importantly, the Carbon nitride preserves its graphitic stacking even in the spatial confinement introduced by the surrounding silica phase. As both precursors are liquids this approach allows convenient shaping into thin and thick films or monoliths of mesoporous Carbon Nitrides. Enhanced photocatalytic activity is observed for the production of hydrogen from water when these mesoporous Carbon Nitrides are applied as photocatalyst in comparison to the bulk, but also to other mesoporous Carbon Nitrides, prepared by the reported two-step, hard templating approach.

  • mesoporous 2d hexagonal Carbon nitride and titanium nitride Carbon composites
    Advanced Materials, 2009
    Co-Authors: Youngsi Jun, Markus Antonietti, Won Hi Hong, Arne Thomas
    Abstract:

    Carbon and metal Nitrides are appealing classes of materials, astheir properties can complement Carbon, on the one hand, andmetal oxides, on the other, in a variety of applications. A largernumber of reports in the literature concern the synthesis ofdifferent modifications of Carbon Nitrides, while at ambientconditions graphitic-C

Mohammad Ziaur Rahman - One of the best experts on this subject based on the ideXlab platform.

  • reduced recombination and low resistive transport of electrons for photo redox reactions in metal free hybrid photocatalyst
    Applied Physics Letters, 2018
    Co-Authors: Mohammad Ziaur Rahman, Youhong Tang, P Kwong
    Abstract:

    Photoinduced charge separation against their faster recombination is a rate determinant for photocatalytic proton reduction to hydrogen. Dissociation of electron-hole pairs into free electrons and holes in Carbon Nitrides greatly suffered from the inherent high recombination rate. This study has shown that coupling two energetically optimized, but with different phases Carbon Nitrides in the form of hybrid could significantly inhibit the charge carrier recombination and facilitate the overall charge transfer processes. It is also found that the potential gradient in this homojunction delocalizes electrons and holes, and increases the spatial charge separation. Therefore, this leads to a record high apparent quantum efficiency of 5% for photocatalytic H2 production from water under visible light irradiation in the absence of a precious metal (e.g., Pt) cocatalyst.Photoinduced charge separation against their faster recombination is a rate determinant for photocatalytic proton reduction to hydrogen. Dissociation of electron-hole pairs into free electrons and holes in Carbon Nitrides greatly suffered from the inherent high recombination rate. This study has shown that coupling two energetically optimized, but with different phases Carbon Nitrides in the form of hybrid could significantly inhibit the charge carrier recombination and facilitate the overall charge transfer processes. It is also found that the potential gradient in this homojunction delocalizes electrons and holes, and increases the spatial charge separation. Therefore, this leads to a record high apparent quantum efficiency of 5% for photocatalytic H2 production from water under visible light irradiation in the absence of a precious metal (e.g., Pt) cocatalyst.

  • reduced recombination and low resistive transport of electrons for photo redox reactions in metal free hybrid photocatalyst
    Applied Physics Letters, 2018
    Co-Authors: Mohammad Ziaur Rahman, Youhong Tang, P Kwong
    Abstract:

    Photoinduced charge separation against their faster recombination is a rate determinant for photocatalytic proton reduction to hydrogen. Dissociation of electron-hole pairs into free electrons and holes in Carbon Nitrides greatly suffered from the inherent high recombination rate. This study has shown that coupling two energetically optimized, but with different phases Carbon Nitrides in the form of hybrid could significantly inhibit the charge carrier recombination and facilitate the overall charge transfer processes. It is also found that the potential gradient in this homojunction delocalizes electrons and holes, and increases the spatial charge separation. Therefore, this leads to a record high apparent quantum efficiency of 5% for photocatalytic H2 production from water under visible light irradiation in the absence of a precious metal (e.g., Pt) cocatalyst.