Strong Tribocatalytic Nitrogen Fixation of Graphite Carbon Nitride g-C3N4 through Harvesting Friction Energy

Effect of Strontium Substitution on the Tribocatalytic Performance of Barium Titanate

This study investigates the impact of Sr doping on the tribocatalytic performance of BaTiO₃ in degrading organic pollutants. Ba_1-xSr_xTiO₃ (x = 0-0.3) nanopowders are synthesized and their tribocatalytic performance evaluated. By doping Sr into BaTiO₃, the tribocatalytic performance was enhanced, resulting in an approximately 35% improvement in the degradation efficiency of Rhodamine B using Ba_0.8Sr_0.2TiO₃. Factors such as the friction contact area, stirring speed, and materials of the friction pairs also influenced the dye degradation. Electrochemical impedance spectroscopy revealed that Sr doping improved BaTiO₃'s charge transfer efficiency, thereby boosting its tribocatalytic performance. These findings indicate potential applications for Ba_1-xSr_xTiO₃ in dye degradation processes.

Piezoelectrically enhanced photocatalysis of KxNa1-xNbO3 (KNN) microstructures for efficient water purification

As a kind of excellent multifunctional metal oxide semiconductor, K_xNa_1-xNbO₃ (KNN) has been widely applied in a variety of fields such as photocatalysis and energy harvesting due to its excellent piezoelectric, dielectric and photovoltaic properties in recent decades. In this report, octahedron-shaped K_0.4Na_0.6NbO₃ (KNN-6) microstructures assembled by cubic nanoparticles with {010} exposed facets were synthesized via a one-pot hydrothermal reaction. Due to the accumulation of electrons on the exposed facets, which was conducive to the separation of photo-generated electron-hole pairs, the microstructures could achieve a highly efficient photocatalytic performance for wastewater degradation. In addition, owing to the piezoelectric effect of KNN crystals, the degradation efficiency could be further enhanced by introducing ultrasonic vibration. Using methylene blue (MB) as the organic dye to evaluate their wastewater degradation efficiency, the KNN microstructures achieved their best catalytic performance when the atomic ratio of KOH to NaOH in the reactant was set at 4 : 6 (KNN-6). Under the synergistic effect of light irradiation and ultrasonic vibration, MB could almost be completely (99%) degraded within 40 minutes by KNN-6 microstructures, which was several times more efficient than that of pure NaNbO₃ or KNbO₃ in previous reports. This work demonstrated that the K_0.4Na_0.6NbO₃ (KNN-6) microstructure could be a prominent candidate for wastewater purification. The formation mechanism of KNN crystals and the role of the piezoelectric effect in the photocatalytic process were also discussed.

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.

Lead-Free Bi0.5Na0.5TiO3 Ferroelectric Nanomaterials for Pyro-Catalytic Dye Pollutant Removal under Cold-Hot Alternation

In this work, explicitly pyro-catalytic performance is observed in sol-gel-synthesized ferroelectric Bi_0.5Na_0.5TiO₃ lead-free nanomaterials, and its application for dye wastewater purification is also actualized under temperature fluctuations varying from 23 °C to 63 °C. The decomposition ratios of the pyro-catalytic Bi_0.5Na_0.5TiO₃ nanomaterials on Rhodamine B, methyl blue and methyl orange can reach 96.75%, 98.35% and 19.97%, respectively. In the pyro-catalytic process, the probed active species such as hydroxyl radicals, superoxide radicals and holes play an extremely important role in decomposing dye molecules. The ferroelectric Bi_0.5Na_0.5TiO₃ lead-free nanomaterials will have an excellent prospect for dye wastewater purification due to its explicit pyro-catalysis.

One-pot construction of highly efficient TaON/Bi2O3/S-BiOCl ternary photocatalysts: Simultaneously integrating type-Ⅰ with Z-scheme junctions for improved visible light-driven removal of organic pollutants

Bismuth oxychloride (BiOCl) has appeared as a popular candidate in photocatalysis field but is plagued by its poor visible light harvesting and low carriers-flow steering inherited from wide band gap. Integration of doping and heterojunction engineering into the bulk has proven to be an optimal and generally applied method for enabling excellent photocatalytic activity. Nevertheless, the previous reported BiOCl-based photocatalysts fabricated by the above strategies are still suffered from harsh synthesis process, poor interface stability and narrow application area. Here, we introduce a facile one-pot hydrothermal strategy to achieve in-situ growth of TaON as a medium on the surface of Bi₂O₃ and S-doped BiOCl (denoted as S-BiOCl) for constructing ternary TaON/Bi₂O₃/S-BiOCl heterostructures, which were obtained by the simultaneous coprecipitation and ripening process. Current investigation suggests that such a unique TaON/Bi₂O₃/S-BiOCl exhibits a relatively much higher photocatalytic activity for visible light-driven removal of rhodamine B (RhB), tetracycline (TC) and tetracycline hydrochloride (TC-HCl) than those of hybrid Bi₂O₃/S-BiOCl and pristine S-BiOCl. It is ascribed to the synergetic effect on the introduction of S dopant level in BiOCl lattice as well as the construction of intimate double heterointerfaces among Bi₂O₃, TaON and S-BiOCl, which endows the TaON/Bi₂O₃/S-BiOCl photocatalysts with considerable advantages for highly elevating photocatalytic performances, such as the intensive optical absorption, high redox potential as well as high-efficient photocharge separation originated from type-I and Z-scheme pathways. This work delivers novel insights for design and one-pot preparation of high-active BiOX (X = Cl, Br and I)-based photocatalysts towards organic dye and antibiotic removal in the future research.

Ultrafast plasma method allows rapid immobilization of monatomic copper on carboxyl-deficient g-C3N4 for efficient photocatalytic hydrogen production

Transition-metal monometallic photocatalysts have received extensive attention owing to the maximization of atomic utilization efficiency. However, in previous related works, single-atom loading and stability are generally low due to limited anchor sites and mechanisms. Recently, adding transition-metal monatomic sites to defective carbon nitrides has a good prospect, but there is still lack of diversity in defect structures and preparation techniques. Here, a strategy for preparing defect-type carbon-nitride–coupled monatomic copper catalysts by an ultrafast plasma method is reported. In this method, oxalic acid and commercial copper salt are used as a carboxyl defect additive and a copper source, respectively. Carbon nitride samples containing carboxyl defects and monatomic copper can be processed within 10 min by one-step argon plasma treatment. Infrared spectroscopy and nuclear magnetic resonance prove the existence of carboxyl defects. Spherical aberration electron microscopy and synchrotron radiation analysis confirm the existence of monatomic copper. The proportion of monatomic copper is relatively high, and the purity is high and very uniform. The Cu PCN as-prepared shows not only high photo-Fenton pollutant degradation ability but also high photocatalytic hydrogen evolution ability under visible light. In the photocatalytic reaction, the reversible change of Cu⁺/Cu²⁺ greatly promotes the separation and transmission of photogenerated carriers and improves the utilization of photoelectrons. The photocatalytic hydrogen evolution rate of the optimized sample is 8.34 mmol g⁻¹·h⁻¹, which is 4.54 times that of the raw carbon nitride photocatalyst. The cyclic photo-Fenton experiment confirms the catalyst has excellent repeatability in a strong oxidation environment. The synergistic mechanism of the photocatalyst obtained by this plasma is the coordination of single-atom copper sites and carboxyl defect sites. The single copper atoms incorporated can act as an electron-rich active center, enhancing the h+ adsorption and reduction capacity of Cu PCN. At the same time, the carboxyl defect sites can form hydrogen bonds to stabilize the production of hydrogen atoms and subsequently convert them to hydrogen because of the unstable hydrogen bond structure. This plasma strategy is green, convenient, environment-friendly, and waste-free. More importantly, it has the potential for large-scale production, which brings a new way for the general preparation of high-quality monatomic catalysts.