Alkaline Salt-Promoted Construction of Hydrophilic and Nitrogen Deficient Graphitic Carbon Nitride with Highly Improved Photocatalytic Efficiency
02 Mar 2021-Journal of Materials Chemistry (Royal Society of Chemistry (RSC))-Vol. 9, Iss: 8, pp 4700-4706
TL;DR: In this paper, a facile construction methodology was demonstrated to afford g-C3N4 with abundant N vacancies, high crystallinity, a hydrophilic surface structure, a small particle size, and an increased surface area under neat and mild conditions.
Abstract: Graphitic carbon nitride (g-C3N4) possesses fascinating merits, but its practical applications are limited by the inferior properties of limited visible-light sorption, rapid recombination of photo-excited charge carriers and low electrical conductivity. Introduction of N-defects is an efficient approach to tune its optical properties, but strategies capable of creating abundant vacancies and simultaneously maintaining the highly crystalline architecture are still limited and highly desired. In this work, a facile construction methodology was demonstrated to afford g-C3N4 with abundant N vacancies, high crystallinity, a hydrophilic surface structure, a small particle size, and an increased surface area under neat and mild conditions. The essence of our approach lies in the treatment of the bulk g-C3N4 precursor with an alkaline salt (LiN(SiMe3)2) with a low melting point, moderate nucleophilicity, and easy removal procedures. The unique structural properties of the afforded ND-g-C3N4 allow for a significantly redshifted absorption edge and enhanced charge carrier separation, leading to superior photocatalytic hydrogen evolution performance three times that obtained by pristine g-C3N4. The modification strategy developed herein sheds light on the fabrication of g-C3N4-based materials with improved photocatalytic efficiency via efficient introduction of N defects, variation of the surface structure, and retention of the high crystallinity.
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TL;DR: Wang et al. as mentioned in this paper developed a defect engineering strategy to construct N-deficient ordered mesoporous graphitic carbon nitride coupled with AgPd nanoparticles, and the as-prepared Ag0.1Pd0.9/N-ompg-C3N4 catalyst exhibits remarkable activity with the Turnover frequency (TOF) value of 1588.2h−1 and robust stability with only a slight decrease in activity after ten cycles.
43 citations
TL;DR: Wang et al. as mentioned in this paper developed a defect engineering strategy to construct N-deficient ordered mesoporous graphitic carbon nitride coupled with AgPd nanoparticles, and the as-prepared Ag0.1Pd0.9/N-ompg-C3N4 catalyst exhibits remarkable activity with the Turnover frequency (TOF) value of 1588.2 h−1 and robust stability with only a slight decrease in activity after ten cycles.
42 citations
TL;DR: In this paper, a new supramolecular assembly family as reactants was designed to synthesize highly photoactive porous polymeric carbon nitride (CN), based on a melem-constructed honeycomb, coupled with the insertion of small triazine analogs.
Abstract: We design a new supramolecular assembly family as reactants to synthesize highly-photoactive porous polymeric carbon nitride (CN), based on a melem-constructed honeycomb, coupled with the insertion of small triazine analogs. The inclusion of small molecules into the melem-based hexameric rings leads to a highly porous CN with controlled electronic, optical, and catalytic properties, as proven by experimental and theoretical studies. The best-performing photocatalyst demonstrates state-of-the-art activity for hydrogen evolution reaction (HER, H2 generation rate of 8075 μmol h−1 g−1), and CO2 reduction (CO2RR, CO production of 1125 μmol g−1 within 3 h) with high quantum yield efficiencies and excellent stability, owing to the enhanced charge separation and light absorption, appropriate energy bands position, and high specific surface area.
15 citations
TL;DR: In this paper , facial thermal polymerization of melamine-cyanuric acid supramolecular precursors under H2 flow was used to synthesize defective g-C3N4 (BCN) microrods with an increased specific surface area.
14 citations
TL;DR: In this paper, a metal-free photocatalyst is constructed by anchoring the ultrasmall SiC nanocrystals on carbon nitride (CN) nanosheets for efficient and durable hydrogen generation.
Abstract: Photocatalytic hydrogen evolution from water is a promising approach for renewable energy generation and storage. However, traditional photocatalysts suffer from limited hydrogen evolution rates due to the lack of active sites. In this work, we demonstrate that a plenty of active sites can be provided by the surface autocatalytic effect and quantum confinement of ultrasmall SiC nanocrystals (NCs). A metal-free photocatalyst is constructed by anchoring the ultrasmall SiC NCs on carbon nitride (CN) nanosheets for efficient and durable hydrogen generation. Moreover, the optical absorption in the visible range and the separation of electrons and holes are significantly improved by the heterojunction band alignment. As a consequence, the CN/SiC NC composite exhibits a high hydrogen evolution rate up to 1889 μmol g−1 h−1 under visible light irradiation with an apparent quantum yield (AQY) of 9.8% at 420 nm. And the photocatalyst shows high stability in the cyclic test. This work provides a new strategy to develop highly efficient photocatalysts for hydrogen generation via the surface autocatalytic effect and quantum confinement.
9 citations
References
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TL;DR: It is shown that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor.
Abstract: The production of hydrogen from water using a catalyst and solar energy is an ideal future energy source, independent of fossil reserves. For an economical use of water and solar energy, catalysts that are sufficiently efficient, stable, inexpensive and capable of harvesting light are required. Here, we show that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor. Contrary to other conducting polymer semiconductors, carbon nitride is chemically and thermally stable and does not rely on complicated device manufacturing. The results represent an important first step towards photosynthesis in general where artificial conjugated polymer semiconductors can be used as energy transducers.
9,751 citations
TL;DR: It is anticipated that this review can stimulate a new research doorway to facilitate the next generation of g-C3N4-based photocatalysts with ameliorated performances by harnessing the outstanding structural, electronic, and optical properties for the development of a sustainable future without environmental detriment.
Abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...
5,054 citations
TL;DR: The unique advances on ultrathin 2D nanomaterials are introduced, followed by the description of their composition and crystal structures, and the assortments of their synthetic methods are summarized.
Abstract: Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...
3,628 citations
TL;DR: This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials, and highlights crucial issues that should be addressed in future research activities.
Abstract: Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.
3,265 citations
TL;DR: In this article, a top-down thermal oxidation etching of bulk g-C3N4 in air has been shown to improve the photocatalytic activities of the material in terms of OH radical generation and hydrogen evolution.
Abstract: Graphitic (g)-C3N4 with a layered structure has the potential of forming graphene-like nanosheets with unusual physicochemical properties due to weak van der Waals forces between layers. Herein is shown that g-C3N4 nanosheets with a thickness of around 2 nm can be easily obtained by a simple top-down strategy, namely, thermal oxidation etching of bulk g-C3N4 in air. Compared to the bulk g-C3N4, the highly anisotropic 2D-nanosheets possess a high specific surface area of 306 m2 g-1, a larger bandgap (by 0.2 eV), improved electron transport ability along the in-plane direction, and increased lifetime of photoexcited charge carriers because of the quantum confinement effect. As a consequence, the photocatalytic activities of g-C3N4 nanosheets have been remarkably improved in terms of OH radical generation and photocatalytic hydrogen evolution.
2,900 citations