Superior sponge-like carbon self-doping graphitic carbon nitride nanosheets derived from supramolecular pre-assembly of a melamine-cyanuric acid complex for photocatalytic H2 evolution

Hydrophilic/hydrophobic heterojunctions for enhanced photocatalytic hydrogen evolution via gas release dynamics

Covalent-organic frameworks (COFs), characterized by their exceptional light absorption and ordered architecture, have emerged as potential candidates for photocatalytic hydrogen production. In this work, we discovered that the incorporation of fluorine into the sub-nanocavity of azine-linked COF (TF-COF) not only augments its hydrophobicity but also strengthens the interaction between Pt cocatalysts and COFs. In an effort to enhance photocatalytic water splitting efficiency, we integrated the hydrophobic TF-COF with the hydrophilic carbon nitride (CN) to construct a hydrophilic/hydrophobic heterojunction (CTF-x heterojunction). Both experimental results and density functional theory (DFT) calculations reveal that the hydrophilic side, CN, aids in the adsorption and transfer of water molecules, whereas the hydrophobic side, TF-COF, generates hydrogen and promotes its overflow, thereby achieving space charge separation. The hydrogen evolution activity of CTF-50 % (with a CN content of 50 %) reached an optimal value of 2428 μmol g-1h-1, with an apparent quantum yield (AQY) of 2.6 % at 400 nm. This is approximately four times higher than that of pure CN and ten times greater than that of TF-COF. We believe this work will provide valuable insights for developing efficient heterojunction photocatalysts.

Emerging Roles of Graphitic Carbon Nitride-based Materials in Biomedical Applications

Graphite carbon nitride (g-C3N4) is a two-dimensional conjugated polymer with a unique energy band structure similar to graphene. Due to its outstanding analytical advantages, such as relatively small band gap (2.7 eV), low-cost synthesis, high thermal stability, excellent photocatalytic ability, and good biocompatibility, g-C3N4 has attracted the interest of researchers and industry, especially in the medical field. This paper summarizes the latest research on g-C3N4-based composites in various biomedical applications, including therapy, diagnostic imaging, biosensors, antibacterial, and wearable devices. In addition, the application prospects and possible challenges of g-C3N4 in nanomedicine are also discussed in detail. This review is expected to inspire emerging biomedical applications based on g-C3N4.

Polydopamine Coating of Graphitic Carbon Nitride, g-C3N4, Improves Biomedical Application

Graphitic carbon nitride (g-C3N4) is an intriguing nanomaterial that exhibits photoconductive fluorescence properties under UV-visible light. Dopamine (DA) coating of g-C3N4 prepared from melamine was accomplished via self-polymerization of DA as polydopamine (PDA). The g-C3N4 was coated with PDA 1, 3, and 5 times repeatedly as (PDA@g-C3N4) in tris buffer at pH 8.5. As the number of PDA coatings was increased on g-C3N4, the peak intensity at 1512 cm-1 for N-H bending increased. In addition, the increased weight loss values of PDA@g-C3N4 structures at 600 °C from TGA thermograms confirmed that the coating was accomplished. The band gap of g-C3N4, 2.72 eV, was reduced to 0.87 eV after five coatings with PDA. A pristine g-C3N4 was found to have an isoelectric point (IEP) of 4.0, whereas the isoelectric points of 1PDA@g-C3N4 and 3PDA@g-C3N4 are close to each other at 3.94 and 3.91, respectively. On the other hand, the IEP of 5PDA@g-C3N4 was determined at pH 5.75 assuming complete coating with g-C3N4. The biocompatibility of g-C3N4 and PDA@g-C3N4 against L929 fibroblast cell lines revealed that all PDA@g-C3N4 coatings were found to be biocompatible up to a 1000 mg/mL concentration, establishing that PDA coatings did not adversely affect the biocompatibility of the composite materials. In addition, PDA@g-C3N4 was screened for antioxidant potential via total phenol content (TPC) and total flavonoid content assays and it was found that PDA@g-C3N4 has recognizable TPC values and increased linearly with an increased number of PDA coatings. Furthermore, blood compatibility of pristine g-C3N4 is enhanced considerably upon PDA coating, affirmed by hemolysis and the blood clotting index%. Additionally, α-glucosidase inhibitory properties of PDA@g-C3N4 structures revealed that 67.6 + 9.8% of this enzyme was evenly inhibited by 3PDA@g-C3N4 structure.

Metal-organic frameworks incorporated with C3N4: A visible light enhanced platform for degradation of polybromodiphenyl ethers

A series of nano-photocatalysts metal-organic frameworks (MOFs)/graphitic carbon nitride (CN) (named MOFCN-x) with high activity have been synthesized by in-situ growth method. Under visible light irradiation, MOFCN-x hybrids show enhanced photocatalytic activity for the debromination of polybromodiphenyl ethers (PBDEs) compared with CN. Among all the hybrids, MOFCN-2 shows the highest reaction rate, which is 3.3 times as high as that in CN. MOFCN-x photocatalysts own stable visible light activity after recycled experiment. It indicates that a moderate amount of MOFs in MOFCN-x can largely enhance the photocatalytic ability by improved visible light absorption, larger specific surface area and better photo-generated charge carriers separation and transfer capabilities. More interestingly, the debromination pathway of PBDEs by MOFCN-x shows obvious selectivity compared with pure CN that bromines at meta-positions are much more susceptible than those at the para- and ortho-positions. The possible photoreductive mechanism has been proposed. This study shows that nanocomposite MOFCN can be an excellent candidate for dealing with halogen pollutants by solar-driven.

Controllable Anchoring of Graphitic Carbon Nitride on MnO2 Nanoarchitectures for Oxygen Evolution Electrocatalysis

The design and fabrication of eco-friendly and cost-effective (photo)electrocatalysts for the oxygen evolution reaction (OER) is a key research goal for a proper management of water splitting to address the global energy crisis. In this work, we focus on the preparation of supported MnO2/graphitic carbon nitride (g-CN) OER (photo)electrocatalysts by means of a novel preparation strategy. The proposed route consists of the plasma enhanced-chemical vapor deposition (PE-CVD) of MnO2 nanoarchitectures on porous Ni scaffolds, the anchoring of controllable g-CN amounts by an amenable electrophoretic deposition (EPD) process, and the ultimate thermal treatment in air. The inherent method versatility and flexibility afforded defective MnO2/g-CN nanoarchitectures, featuring a g-CN content and nano-organization tunable as a function of EPD duration and the used carbon nitride precursor. Such a modulation had a direct influence on OER functional performances, which, for the best composite system, corresponded to an overpotential of 430 mV at 10 mA/cm2, a Tafel slope of ≈70 mV/dec, and a turnover frequency of 6.52 × 10-3 s-1, accompanied by a very good time stability. The present outcomes, comparing favorably with previous results on analogous systems, were rationalized on the basis of the formation of type-II MnO2/g-CN heterojunctions, and yield valuable insights into this class of green (photo)electrocatalysts for end uses in solar-to-fuel conversion and water treatment.

Recent Progress in Doped g-C3N4 Photocatalyst for Solar Water Splitting: A Review

Graphitic carbon nitride (g-C₃N₄) photocatalysis for water splitting is harvested as a fascinating way for addressing the global energy crisis. At present, numerous research subjects have been achieved to design and develop g-C₃N₄ photocatalysis, and the photocatalytic system still suffers from low efficiency that is far from practical applications. Here, there is an inspiring review on the latest progress of the doping strategies to modify g-C₃N₄ for enhancing the efficiency of photocatalytic water splitting, including non-metal doping, metal doping, and molecular doping. Finally, the review concludes a summary and highlights some perspectives on the challenges and future research of g-C₃N₄ photocatalysts.

Which Is More Efficient in Promoting the Photocatalytic H2 Evolution Performance of g-C3N4: Monometallic Nanocrystal, Heterostructural Nanocrystal, or Bimetallic Nanocrystal?

Generally, an excellent cocatalyst could promote the photocatalytic hydrogen (H₂) evolution performance of g-C₃N₄ significantly. Herein, a superior cocatalyst of gold-platinum (AuPt) nanocrystal with an ultralow content of Pt was successfully decorated on carbon self-doping g-C₃N₄ nanosheets (AuPt/CCN) via a facile photodeposition route. The corresponding Pt/CCN, Au/CCN, Au/Pt/CCN, and Pt/Au/CCN were also prepared for comparison. It is found that AuPt/CCN exhibits much superior photocatalytic H₂ evolution performance (1135 μmol/h) when irradiated with a 300 W Xe lamp, up to 20, 12, 5, 2, and 1.5 times that of the pristine CCN, Pt/CCN, Au/CCN, Au/Pt/CCN, and Pt/Au/CCN, respectively. The quantum efficiency (QE) of AuPt/CCN at 420 nm reaches 12.5%. The experimental and density functional theory calculation results suggested that the improved AuPt performance can be mainly ascribed to the non-plasmon-related synergistic effect of Au and Pt atoms in AuPt nanocrystal: (1) the proximity and the electronegativity difference of Au and Pt atoms in AuPt accelerate the transfer and separation of charge carriers and (2) the synergistic interaction between Pt and Au atoms optimizes the Gibbs free energy (ΔG_H*) of H* (atom) adsorption on AuPt, promoting the H₂ generation kinetics of AuPt/CCN.

The preparation of Al2O3/g-C3N4 composites in aluminum–water self-assembly system and its improved photocatalytic properties

The aluminum alloy is used as the aluminum source, together with melamine and cyanuric acid, in a water reaction system to obtain the precursor of Al2O3/g-C3N4 through self-assembly in one step, and then calcined to obtain the Al2O3/g-C3N4 composite photocatalytic material.