Achieving Highly Efficient Photocatalytic Hydrogen Evolution through the Construction of g-C3N4@PdS@Pt Nanocomposites

Selective supported catalysts have emerged as a promising approach to enhance carrier separation, particularly in the realm of photocatalytic hydrogen production. Herein, a pioneering exploration involves the loading of PdS and Pt catalyst onto g-C3N4 nanosheets to construct g-C3N4@PdS@Pt nanocomposites. The photocatalytic activity of nanocomposites was evaluated under visible light and full spectrum irradiation. The results show that g-C3N4@PdS@Pt nanocomposites exhibit excellent properties. Under visible light irradiation, these nanocomposites exhibit a remarkable production rate of 1289 μmol·g-1·h-1, marking a staggering 60-fold increase compared to g-C3N4@Pt (20.9 μmol·g-1·h-1). Furthermore, when subjected to full spectrum irradiation, the hydrogen production efficiency of g-C3N4@PdS@Pt-3 nanocomposites reaches an impressive 11,438 μmol·g-1·h-1, representing an eightfold enhancement compared to g-C3N4@Pt (1452 μmol·g-1·h-1) under identical conditions. Detailed investigations into the microstructure and optical properties of g-C3N4@PdS catalysts were conducted, shedding light on the mechanisms governing photocatalytic hydrogen production. This study offers valuable insights into the potential of these nanocomposites and their pivotal role in advancing photocatalysis.

Facile Fabrication of TiO2 Quantum Dots-Anchored g-C3N4 Nanosheets as 0D/2D Heterojunction Nanocomposite for Accelerating Solar-Driven Photocatalysis

TiO₂ semiconductors exhibit a low catalytic activity level under visible light because of their large band gap and fast recombination of electron-hole pairs. This paper reports the simple fabrication of a 0D/2D heterojunction photocatalyst by anchoring TiO₂ quantum dots (QDs) on graphite-like C₃N₄ (g-C₃N₄) nanosheets (NSs); the photocatalyst is denoted as TiO₂ QDs@g-C₃N₄. The nanocomposite was characterized via analytical instruments, such as powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, t orange (MO) under solar light were compared. The TiO₂ QDs@g-C₃N₄ photocatalyst exhibited 95.57% MO degradation efficiency and ~3.3-fold and 5.7-fold higher activity level than those of TiO₂ QDs and g-C₃N₄ NSs, respectively. Zero-dimensional/two-dimensional heterojunction formation with a staggered electronic structure leads to the efficient separation of photogenerated charge carriers via a Z-scheme pathway, which significantly accelerates photocatalysis under solar light. This study provides a facile synthetic method for the rational design of 0D/2D heterojunction nanocomposites with enhanced solar-driven catalytic activity.

Remarkable Pyro-Catalysis of g-C3N4 Nanosheets for Dye Decoloration under Room-Temperature Cold-Hot Cycle Excitation

Pyroelectric materials have the ability to convert the environmental cold-hot thermal energy such as day-night temperature alternation into electrical energy. The novel pyro-catalysis technology can be designed and realized on the basis of the product coupling between pyroelectric and electrochemical redox effects, which is helpful for the actual dye decomposition. The organic two-dimensional (2D) graphic carbon nitride (g-C₃N₄), as an analogue of graphite, has attracted considerable interest in the field of material science; however, its pyroelectric effect has rarely been reported. In this work, the remarkable pyro-catalytic performance was achieved in the 2D organic g-C₃N₄ nanosheet catalyst materials under the continuous room-temperature cold-hot thermal cycling excitation from 25 °C to 60 °C. The pyro-catalytic RhB dye decoloration efficiency of the 2D organic g-C₃N₄ can reach ~92.6%. Active species such as the superoxide radicals and hydroxyl radicals are observed as the intermediate products in the pyro-catalysis process of the 2D organic g-C₃N₄ nanosheets. The pyro-catalysis of the 2D organic g-C₃N₄ nanosheets provides efficient technology for wastewater treatment applications, utilizing the ambient cold-hot alternation temperature variations in future.

C3N4 nanosheet-supported Prussian Blue nanoparticles as a peroxidase mimic: colorimetric enzymatic determination of lactate

Prussian Blue nanoparticles were deposited on g-C₃N₄ nanosheets. The resulting nanocomposite possesses peroxidase-like (POx) activity and can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine at room temperature in the presence of H₂O₂. This leads to formation of a blue product with an absorption maximum at 650 nm. The formation of the Prussian Blue nanoparticles on the g-C₃N₄ nanosheets, and the POx-like activity of the composite were characterized in detail. The POx mimic was used for determination of L-lactic acid via detection of H₂O₂ that is produced by the enzyme lactate oxidase (LOx). The assay has a linear range that extends from 5 to 100 μM, and the detection limit is 2.2 μM. The method was successfully applied to the determination of L-lactic acid in spiked human serum. Graphical abstract Ultra-small Prussian Blue (PB) nanoparticles were used to modify g-C₃N₄ nanosheets, and their peroxidase-like activity was explored for detection of L-lactic acid. LOx represent L-lactate oxidase, and TMB represents 3,3',5,5'-tetramethylbenzidine.

Highly Selective and Sensitive Detection of Hg2+ Based on Förster Resonance Energy Transfer between CdSe Quantum Dots and g-C3N4 Nanosheets

In the presence of Hg2+, a fluorescence resonance energy transfer (FRET) system was constructed between CdSe quantum dots (QDs) (donor) and g-C3N4 (receptors). Nanocomposites of g-C3N4 supported by CdSe QDs (CdSe QDs/g-C3N4 nanosheets) were fabricated through an electrostatic interaction route in an aqueous solution. The nanocomposites were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Results showed that the g-C3N4 nanosheets were decorated randomly by CdSe QDs, with average diameter of approximately 7 nm. The feasibility of the FRET system as a sensor was demonstrated by Hg (II) detection in water. At pH 7, a linear relationship was observed between the fluorescence intensity and the concentration of Hg (II) (0-32 nmol/L), with a detection limit of 5.3 nmol/L. The new detection method was proven to be sensitive for detecting Hg2+ in water solutions. Moreover, the method showed high selectivity for Hg2+ over several metal ions, including Na+, Mg2+, Ca2+, Pb2+, Cr3+, Cd2+, Zn2+, and Cu2+. The CdSe QDs/g-C3N4 nanosheet conjugate exhibited desirable long-term stability and reversibility as a novel FRET sensor. The novel FRET-based fluorescence detection provided an attractive assay platform for quantifying Hg2+ in complex water solutions.

Highly Sensitive Acetone Gas Sensor Based on g-C₃N₄ Decorated MgFe₂O₄ Porous Microspheres Composites

The g-C₃N₄ decorated magnesium ferrite (MgFe₂O₄) porous microspheres composites were successfully obtained via a one-step solvothermal method. The structure and morphology of the as-prepared MgFe₂O₄/g-C₃N₄ composites were characterized by the techniques of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermal gravity and differential scanning calorimeter (TG–DSC) and N₂-sorption. The gas sensing properties of the samples were measured and compared with a pure MgFe₂O₄-based sensor. The maximum response of the sensor based on MgFe₂O₄/g-C₃N₄ composites with 10 wt % g-C₃N₄ content to acetone is improved by about 145 times, while the optimum temperature was lowered by 60 °C. Moreover, the sensing mechanism and the reason for improving gas sensing performance were also discussed.

Enhancement of Rhodamine B Degradation by Ag Nanoclusters-Loaded g-C₃N₄ Nanosheets

In this paper, silver (Ag) nanoclusters-loaded graphitic carbon nitride (g-C₃N₄) nanosheets are synthesized and their physical properties as well as photocatalytic activities are systematically investigated by different techniques. The existence of Ag atoms in the form of nanoclusters (NCs) rather than well-crystallized nanoparticles are evidenced by X-ray diffraction patterns, SEM images, and XPS spectra. The deposition of Ag nanoclusters on the surface of g-C₃N₄ nanosheets affect the crystal structure and slightly reduce the band gap energy of g-C₃N₄. The sharp decrease of photoluminescence intensity indicates that g-C₃N₄/Ag heterojunctions successfully prevent the recombination of photo-generated electrons and holes. The photocatalytic activities of as-synthesized photocatalysts are demonstrated through the degradation of rhodamine B (RhB) solutions under Xenon lamp irradiation. It is demonstrated that the photocatalytic activity depends strongly on the molar concentration of Ag⁺ in the starting solution. The g-C₃N₄/Ag heterojunctions prepared from 0.01 M of Ag⁺ starting solution exhibit the highest photocatalytic efficiency and allow 100% degradation of RhB after being exposed for 60 min under a Xenon lamp irradiation, which is four times faster than that of pure g-C₃N₄ nanosheets.