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Dye wastewater has raised a prevalent environmental concern due to its ability to prevent the penetration of sunlight through water, thereby causing a disruption to the aquatic ecosystem. Carbon quantum dots (CQDs) are particularly sought after for their highly tailorable photoelectrochemical and optical properties. Simultaneously, graphitic carbon nitride (g-C3N4) has gained widespread attention due to its suitable band gap energy as well as excellent chemical and thermal stabilities. Herein, a novel boron-doped CQD (BCQD)-hybridized g-C3N4 homojunction (CN) nanocomposite was fabricated via a facile hydrothermal route. The optimal photocatalyst sample, 1-BCQD/CN (with a 1:3 mass ratio of boron to CQD) accomplished a Rhodamine B (RhB, 10 mg/L) degradation efficiency of 96.8% within 4 h under an 18 W LED light irradiation. The kinetic rate constant of 1.39 × 10–2 min−1 achieved by the optimum sample was found to be 3.6- and 2.8-folds higher than that of pristine CN and un-doped CQD/CN, respectively. The surface morphology, crystalline structure, chemical composition and optical properties of photocatalyst samples were characterized via TEM, FESEM-EDX, XRD, FTIR, UV–Vis DRS and FL spectrometer. Based on the scavenging tests, it was revealed that the photogenerated holes (h+), superoxide anions (∙O2–) and hydroxyl radicals (∙OH) were the primary reactive species responsible for the photodegradation process. Overall, the highly efficient 1-BCQD/CN composite with excellent photocatalytic activity could provide a cost-effective and robust means to address the increasing concerns over global environmental pollution. [ABSTRACT FROM AUTHOR]

Universal access to clean water has been a global ambition over the years. Photocatalytic water disinfection through advanced oxidation processes has been regarded as one of the promising methods for breaking down microbials. The forefront of this research focuses on the application of metal‐free photocatalysts for disinfection to prevent secondary pollution. Graphitic carbon nitride (g‐C3N4) has achieved instant attention as a metal‐free and visible‐light‐responsive photocatalyst for various energy and environmental applications. However, the photocatalytic efficiency of g‐C3N4 is still affected by its rapid charge recombination and sluggish electron‐transfer kinetics. In this contribution, two‐dimensionally protonated g‐C3N4 was employed as metal‐free photocatalyst for water treatment and demonstrated 100 % of Escherichia coli within 4 h under irradiation with a 23 W light bulb. The introduction of protonation can modulate the surface charge of g‐C3N4; this enhances its conductivity and provides a "highway" for the delocalization of electrons. This work highlights the potential of conjugated polymers in antibacterial application. [ABSTRACT FROM AUTHOR]

Being the energy glutton and top ranker of greenhouse gas emission, Haber-Bosch is undoubtedly a grand challenge to reaching sustainability and carbon neutrality. Solar-driven nitrogen (N 2) fixation under mild conditions is highly attractive and promising for sustainable ammonia (NH 3) production. However, low conversion efficiency remains as a serious problem yet to be solved due to the difficult activation of strongly non-polar N N bond. In this study, defective and atomically thin g-C 3 N 4 with boron sites was synthesized via a facile decomposition-thermal polymerization technique. The optimum photocatalyst displayed an NH 3 yield of 213.59 μmol g cat −1 h−1 under visible light irradiation (λ > 400 nm) without any hole scavenger, bestowing high suitability for N 2 fixation in pure water. The impressive performance is largely ascribed to the introduction of B species, which could act as the active sites for N 2 adsorption, activation and reduction. Additionally, the atomically thin layer (∼3.25 nm) shortens charge carrier transport pathway while the B atoms and defects suppress quantum size effect as well as extends photo-response through bandgap reduction. These attributes synergistically lead to suppressed electron-hole recombination, efficacious charge transport, enhanced light utilization and enriched catalytic sites for N 2 fixation. As a whole, this work presents an easy strategy to realize efficient N 2 photofixation over a metal-free, low-cost and non-toxic photocatalyst in pure water as a continuous effort in advancing the burgeoning field of photocatalytic N 2 fixation. [Display omitted] • Atomically thin and boron doped g-C 3 N 4 was synthesized via a facile one-step calcination under N 2 atmosphere. • The atomic-thin layers and boron atoms facilitated adsorption and activation of N 2 molecules. • Photo-response was extended through bandgap reduction and charge transfer was accelerated. • The photocatalytic N 2 fixation was carried out in pure water without any reducing agent. [ABSTRACT FROM AUTHOR]

Growing concerns of water pollution by dye pollutants from the textile industry has led to vast research interest to find green solutions to address this issue. In recent years, heterogeneous photocatalysis has harvested tremendous attention from researchers due to its powerful potential applications in tackling many important energy and environmental challenges at a global level. To fully utilise the broad spectrum of solar energy has been a common aim in the photocatalyst industry. This study focuses on the development of an efficient, highly thermal and chemical stable, environmentally friendly and metal-free graphitic carbon nitride (g-C 3 N 4) to overcome the problem of fast charge recombination which hinders photocatalytic performances. Nitrogen-doped carbon quantum dots (NCQDs) known for its high electronic and optical functionality properties is believed to achieve photocatalytic enhancement by efficient charge separation through forming heterogeneous interfaces. Hence, the current work focuses on the hybridisation of NCQDs and g-C 3 N 4 to produce a composite photocatalyst for methylene blue (MB) degradation under LED light irradiation. The optimal hybridisation method and the mass loading required for maximum attainable MB degradation were systematically investigated. The optimum photocatalyst, 1 wt% NCQD/g-C 3 N 4 composite was shown to exhibit a 2.6-fold increase in photocatalytic activity over bare g-C 3 N 4. Moreover, the optimum sample displayed excellent stability and durability after three consecutive degradation cycles, retaining 91.2% of its original efficiency. Scavenging tests were also performed where reactive species, photon-hole (h+) was identified as the primary active species initiating the pollutant degradation mechanism. The findings of this study successfully shed light on the hybridisation methods of NCQDs which improve existing g-C 3 N 4 photocatalyst systems for environmental remediation by utilising solar energy. Image 1 • Nitrogen-doped CQDs were hybridized with g-C 3 N 4 through a facile synthesis approach. • The NCQD/g-C 3 N 4 hybrid showed high efficiency toward MB degradation under LED light. • The best hybridization approach and the effect of NCQD loading on g-C 3 N 4 were studied. • The optimum 1 wt% NCQD/g-C 3 N 4 exhibited a 2.6-fold increase in activity over g-C 3 N 4. • A plausible photocatalytic mechanism over NCQD/g-C 3 N 4 hybrid composite was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-dimensional interface engineering of isotype g-C3N4/g-C3N4 p-n heterojunctions. • Intimate interfacial contact was formed at the isotype phase junction. • p-n junction expedited interfacial charge transfer via a reinforced electric field. • g-C3N4/g-C3N4 heterostructures displayed exceptional photoreduction of CO2 to CH4. The creation of an isotype phase junction has been recognized as an effective means of improving the spatial charge separation and migration in g-C 3 N 4 materials. Nevertheless, due to a lack of electrostatic control in the internal electric field, isotype heterojunction alone is incapable of providing a sufficient driving force to maximize charge carrier transfer. Herein, we present an interface engineering strategy for co-integrating isotype and p-n heterojunctions to fabricate g-C 3 N 4 /g-C 3 N 4 nanohybrids using a facile ultrasonic-assisted self-assembly method. The coherent boundary between the two distinct phases of g-C 3 N 4 demonstrates that an intimate 2D interfacial contact can be easily established by π-π stacking interactions because of their high structural similarities and low lattice strain. Furthermore, their compatible and well-matched electronic band structures led to a staggered type II alignment in the lateral heterojunction, which confers the resulting composite with strong redox ability, efficient exciton dissociation, and desirable optoelectronic characteristics beyond those of the two constituents. Essentially, the isotype and p-n heterojunctions work in tandem to create a robust built-in electric field, allowing for effective interfacial charge steering for directional electron migration from BCN to CN x. Benefiting from these merits, the BCN/CN x nanohybrid manifested remarkable CH 4 generation from photocatalytic CO 2 reduction, outperforming its CN x and BCN counterparts by 1.91 and 6.88-fold, respectively. The midgap states induced by nitrogen defects in CN x also pose a positive effect on the improved photoactivity of the binary composite by acting as an electron reservoir to mediate electron transfer and further impede charge carrier recombination. This proof-of-concept study highlights the significance of interface engineering in charge flow manipulation and utilization for photocatalytic enhancement. [ABSTRACT FROM AUTHOR]