A visible light driven nanocomposite containing AgBr and sheet-like g-C3N4 was prepared by precipitation of AgBr nanoparticles (NPs) onto the surface of g-C3N4 nano-sheets. The composite system showed a significant enhancement in photocatalytic activity with respect to the mono-component systems in the degradation of methyl orange (MO) under visible light irradiation. Different methods including, bulky, thermal oxidation, protonation, and ultra-sonication were used for synthesis of g-C3N4 nanosheets. The resulted g-C3N4 samples were then modified by AgBr NPs via deposition-precipitation (DP) method. Among them, the catalyst containing the ‘protonated g-C3N4’ showed the best photocatalytic activity. The composite with AgBr:g-C3N4 mole ratio of 2:1 containing the ‘protonated g-C3N4’ showed the best activity. Different coupling techniques including: ‘grinding’, ‘grinding-ultra-sonication’, ‘ultra-sonication/deposition-precipitation’ and ‘ultra-sonication/deposition-precipitation/ultra-sonication’ were used for coupling of the protonated g-C3N4 with AgBr NPs. Among these catalysts, two later cases showed the best photocatalytic activities. Among the type II- heterojunction and the direct Z-scheme mechanisms, later case well described the boosted photocatalytic activity of the composite with respect to the mono-component systems.

A visible light driven AgBr/g-C3N4 photocatalyst composite in methyl orange photodegradation: Focus on photoluminescence, mole ratio, synthesis method of g-C3N4 and scavengers

Graphitic carbon nitride (g-C3N4) is a robust organic semiconductor photocatalyst with proven H2 evolution ability. However, its application in a photoelectrochemical system as a photocathode for H2 production is extremely challenging with the majority of reports representing it as a photoanode. Despite research into constructing g-C3N4 photocathodes in recent years, factors affecting an n-type semiconductor's properties as a photocathode are still not well-understood. The current work demonstrates an effective strategy to transform an n-type g-C3N4 photoanode material into an efficient photocathode through introducing electron trap states associated with both N-defects and C-OH terminal groups. As compared to the g-C3N4 photoelectrode, this strategy develops 2 orders of magnitude higher conductivity and 3 orders of magnitude longer-lived shallow-trapped charges. Furthermore, the average OCVD lifetime observed for def-g-C3N4 is 5 times longer than that observed for g-C3N4. Thus, clear photocathode behavior has been observed with negative photocurrent densities of around -10 μA/cm2 at 0 V vs RHE. Open circuit photovoltage decay (OCVD), Mott-Schottky (MS) plot, and transient absorption spectroscopy (TAS) provide consistent evidence that long-lived shallow-trapped electrons that exist at about the microsecond time scale after photoexcitation are key to the photocathode behavior observed for defect-rich g-C3N4, thus further demonstrating g-C3N4 can be both a photoanode and a photocathode candidate.

Insight on Shallow Trap States-Introduced Photocathodic Performance in n-Type Polymer Photocatalysts.

Graphene and other two-dimensional materials (2DMs) have attracted intensive interest for use in energy storage and conversion systems because of their unique structure and remarkable properties. Although significant progress has been made in this field, certain intrinsic limitations obstruct the achievement of desired properties. 2D heterostructures, upon stacking or stitching different 2DMs in well-defined sequences or patterns, could significantly entail drastic changes in their properties, and thereby synergistically combine the merits of individual 2DMs while eliminating their related drawbacks. Herein, we provide a topical review of recent advances in the preparation and characterization of 2D heterostructures for energy-related applications. Firstly, an introduction is given to the definition and importance of 2D heterostructures, followed by their typical categories of vertically stacked heterostructures and horizontal in-plane heterostructures reported so far. Secondly, the state-of-the-art synthesis approaches to fabricate 2D heterostructures, including mechanically aligned transfer, chemical vapor deposition, liquid exfoliation and self-assembly, and layer by layer self-assembly, are introduced in detail. Then, the current status of advanced characterization techniques like scanning probe-, electron-diffraction-, X-ray-, and spectroscopy-based techniques that are critical for the accurate identification of 2D heterostructures and understanding of the performance-enhancing mechanisms of devices is systemically summarized. Furthermore, recent applications of 2D heterostructures in energy storage (e.g., lithium/sodium ion batteries, lithium sulfur batteries, supercapacitors, and micro-supercapacitors) and conversion (e.g., hydrogen/oxygen evolution reactions and photocatalysis) are exemplified to highlight their positive synergistic effect. Finally, future challenges and prospective solutions that may direct the growth of 2D heterostructures and their energy-related applications are proposed.

Recent advances in the preparation, characterization, and applications of two-dimensional heterostructures for energy storage and conversion

The cost-effective, robust, and efficient electrocatalysts for photoelectrochemical (PEC) water-splitting has been extensively studied over the past decade to address a solution for the energy crisis. The interesting physicochemical properties of CuO have introduced this promising photocathodic material among the few photocatalysts with a narrow bandgap. This photocatalyst has a high activity for the PEC hydrogen evolution reaction (HER) under simulated sunlight irradiation. Here, the recent advancements of CuO-based photoelectrodes, including undoped CuO, doped CuO, and CuO composites, in the PEC water-splitting field, are comprehensively studied. Moreover, the synthesis methods, characterization, and fundamental factors of each classification are discussed in detail. Apart from the exclusive characteristics of CuO-based photoelectrodes, the PEC properties of CuO/2D materials, as groups of the growing nanocomposites in photocurrent-generating devices, are discussed in separate sections. Regarding the particular attention paid to the CuO heterostructure photocathodes, the PEC water splitting application is reviewed and the properties of each group such as electronic structures, defects, bandgap, and hierarchical structures are critically assessed.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202007285

Photoelectrochemical Water-Splitting Using CuO-Based Electrodes for Hydrogen Production: A Review

Fe3O4 nanoparticles functionalized GO/g-C3N4 nanocomposite: An efficient magnetic nanoadsorbent for adsorptive removal of organic pollutants

We unprecedentedly report that layered MnO₂ nanosheets were in situ formed onto the surface of covalently bonded graphitic carbon nitride/reduced graphene oxide nanocomposite (g-C₃N₄/rGO), forming sheet-on-sheet structured two dimension (2D) graphitic carbon nitride/reduced graphene oxide/layered MnO₂ ternary nanocomposite (g-C₃N₄/rGO/MnO₂) with outstanding catalytic properties on thermal decomposition of ammonium perchlorate (AP). The covalently bonded g-C₃N₄/rGO was firstly prepared by the calcination of graphene oxide-guanidine hydrochloride precursor (GO-GndCl), following by its dispersion into the KMnO₄ aqueous solution to construct the g-C₃N₄/rGO/MnO₂ ternary nanocomposite. FT-IR, XRD, Raman as well as the XPS results clearly demonstrated the chemical interaction between g-C₃N₄, rGO and MnO₂. TEM and element mapping indicated that layered g-C₃N₄/rGO was covered with thin MnO₂ nanosheets. Furthermore, the obtained g-C₃N₄/rGO/MnO₂ nanocomposite exhibited promising catalytic capacity on thermal decomposition of AP. Upon addition of 2 wt % g-C₃N₄/rGO/MnO₂ ternary nanocomposite as catalyst, the thermal decomposition temperature of AP was largely decreased up by 142.5 °C, which was higher than that of pure g-C₃N₄, g-C₃N₄/rGO and MnO₂, respectively, demonstrating the synergistic catalysis of the as-prepared nanocomposite.

https://www.mdpi.com/2079-4991/7/12/450/pdf

Constructing Sheet-On-Sheet Structured Graphitic Carbon Nitride/Reduced Graphene Oxide/Layered MnO₂ Ternary Nanocomposite with Outstanding Catalytic Properties on Thermal Decomposition of Ammonium Perchlorate.

Novel graphitic carbon nitride/CuO (g-C₃N₄/CuO) nanocomposite was synthesized through a facile precipitation method. Due to the strong ion-dipole interaction between copper ions and nitrogen atoms of g-C₃N₄, CuO nanorods (length 200-300 nm, diameter 5-10 nm) were directly grown on g-C₃N₄, forming a g-C₃N₄/CuO nanocomposite, which was confirmed via X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Finally, thermal decomposition of ammonium perchlorate (AP) in the absence and presence of the prepared g-C₃N₄/CuO nanocomposite was examined by differential thermal analysis (DTA), and thermal gravimetric analysis (TGA). The g-C₃N₄/CuO nanocomposite showed promising catalytic effects for the thermal decomposition of AP. Upon addition of 2 wt % nanocomposite with the best catalytic performance (g-C₃N₄/20 wt % CuO), the decomposition temperature of AP was decreased by up to 105.5 °C and only one decomposition step was found instead of the two steps commonly reported in other examples, demonstrating the synergistic catalytic activity of the as-synthesized nanocomposite. This study demonstrated a successful example regarding the direct growth of metal oxide on g-C₃N₄ by ion-dipole interaction between metallic ions, and the lone pair electrons on nitrogen atoms, which could provide a novel strategy for the preparation of g-C₃N₄-based nanocomposite.

Direct Growth of CuO Nanorods on Graphitic Carbon Nitride with Synergistic Effect on Thermal Decomposition of Ammonium Perchlorate

The invention discloses a g-C3N4/Fe2O3 composite material and its preparation method and use and belongs to the field of material preparation and energetic materials The g-C3N4/Fe2O3 composite material is prepared by compounding of g-C3N4 and nanometer Fe2O3 according to a mass ratio of 95: 5 to 50: 50 The preparation method comprises carrying out ultrasonic dispersion on nanometer Fe2O3 in an ethanol solution, adding g-C3N4 into the solution, carrying out ultrasonic dispersion with continuous stirring, then slowly grinding the mixture in an agate mortar to obtain paste, putting the paste into a vacuum baking oven, carrying out drying and carrying out roasting in a tubular furnace to obtain the g-C3N4/Fe2O3 composite material The g-C3N4/Fe2O3 composite material has good ammonium perchlorate (AP) thermal decomposition catalysis effects and widens a graphite phase carbonitride application field The preparation method has the advantages of simple processes, short operation time, high preparation efficiency, industrial large-scale production and wide application prospect in the energetic material field

g-C3N4/Fe2O3 composite material and its preparation method and use

The invention discloses a CuO/mpg-C3N4 composite material as well as a preparation method and an application thereof. The composite material is compounded by mpg-C3N4 and nano CuO at the mass ratio of (95:5) to (80:20). The preparation method comprises the following preparation steps: ultrasonically dispersing mpg-C3N4 into an ethanol solution; adding C12H25NaO3S, and further ultrasonically dispersing; adding Cu(NO3)2.3H2O, stirring, and continuously dropwise adding a NaOH solution in the stirring process, and then further stirring and reacting for a certain period of time; and filtering, washing and drying the product, and burning in a tube furnace to obtain the CuO/mpg-C3N4 composite material. Two substances of the CuO/mpg-C3N4 composite material prepared by the method have relatively tight contact, and relatively large specific surface area, so as to display relatively good catalysts effect on thermal decomposition of ammonium perchlorate.

CuO/mpg-C3N4 composite material as well as preparation method and application thereof

The invention discloses a method for preparing a porous graphite-phase carbon nitride material. The method includes the following steps that melamine is placed in hot deionized water to be stirred till the melamine is dissolved; after the mixture is cooled to be at the indoor temperature, a HCl aqueous solution is dripped, and white precipitate is formed by stirring; after the product is dried, porous graphite-phase carbon nitride (p-g-C3N4) is obtained through calcination. The graphite-phase carbon nitride material prepared through the method is of a porous structure, and a good catalytic effect is achieved on thermal decomposition of ammonium perchlorate. According to the preparation method, the raw materials can be obtained easily, the process is simple, and product cost is lowered to a great extent; the method is suitable for industrialized mass production, and wide application prospects are achieved in the field of energetic materials.

Chen Yu

Papers

Constructing Sheet-On-Sheet Structured Graphitic Carbon Nitride/Reduced Graphene Oxide/Layered MnO₂ Ternary Nanocomposite with Outstanding Catalytic Properties on Thermal Decomposition of Ammonium Perchlorate.

Direct Growth of CuO Nanorods on Graphitic Carbon Nitride with Synergistic Effect on Thermal Decomposition of Ammonium Perchlorate

g-C3N4/Fe2O3 composite material and its preparation method and use

CuO/mpg-C3N4 composite material as well as preparation method and application thereof

Method for preparing porous graphite-phase carbon nitride material