Accelerating NADH oxidation and hydrogen production with mid-gap states of nitrogen-rich carbon nitride photocatalyst.

Regeneration of electron carriers such as NAD+/NADH is highly desirable and essential for enzymatic conversions. Here, we demonstrate a sustainable strategy for the regeneration of NAD+ as an electron carrier via photon-assisted heterogeneous catalysis. For this, a mid-gap state induced nitrogen-rich polymeric carbon nitride (NPCN) catalyst was synthesized by an additive-assisted thermal copolymerization. Utilizing NPCN as a photocatalyst presented NADH photooxidation efficiency of over 98% and a high hydrogen production rate of 11.18 mmolg-1h-1 with an apparent quantum yield of 9.16% (λ = 420 nm), outperforming other state-of-art metal-free photocatalysts. The experimental and theoretical simulations suggest that mid-gap states in NPCN catalyst are main platform for charge-carrier separation that enhances the overall photocatalytic performance.

Novel CoAl-LDH/g-C3N4/RGO ternary heterojunction with notable 2D/2D/2D configuration for highly efficient visible-light-induced photocatalytic elimination of dye and antibiotic pollutants.

In this study, we fabricate a novel ternary heterojunction comprising CoAl-layered double hydroxide, g-C3N4, and reduced graphene oxide (LDH/CN/RGO) with a notable 2D/2D/2D configuration using a simple one-step hydrothermal method. The visible-light-induced LDH/CN/RGO ternary heterojunctions displayed significantly enhanced photocatalytic performance towards the degradation of aqueous Congo red (CR, dye) and tetracycline (TC, antibiotic) contaminants, which is far superior to that observed for pristine CN (base material), LDH, P25 (reference), and binary CN/RGO and LDH/CN heterojunctions. In particular, the LDH/CN/RGO ternary heterojunction with RGO and LDH contents of 1 wt.% and 15 wt.%, respectively, exhibited the highest degradation activity among all the fabricated catalysts, and it also displayed exceptional stability during recycling experiments. The significant enhancement in the photocatalytic performance and good stability of existing LDH/CN/RGO ternary heterojunctions were primarily attributed to the large intimate interfacial contact between constituent CN, LDH, and RGO prompted by their exceptional 2D/2D/2D arrangement, which accelerates the interfacial charge-transfer processes to effectively hinder the recombination of photoexcited charge carriers. The present study provides new insights into the rational design and fabrication of novel g-C3N4-based 2D/2D/2D layered ternary heterojunctions as high-performance photocatalysts, and promotes their application in addressing diverse energy and environmental issues.

Hierarchical flower-like NiAl-layered double hydroxide microspheres encapsulated with black Cu-doped TiO2 nanoparticles: Highly efficient visible-light-driven composite photocatalysts for environmental remediation.

Herein, highly efficient composite photocatalysts comprising black Cu-doped TiO2 nanoparticles (BCT) encapsulated within hierarchical flower-like NiAl-layered double hydroxide (LDH) microspheres were fabricated via a one-step hydrothermal route. Cu-doping and subsequent reduction treatment led to extended visible-light absorption of TiO2 in the resulting composites, as confirmed by ultraviolet-visible diffuse reflectance spectral analysis. Moreover, thorough investigations confirmed the strong interactions between LDH and BCT in the resulting BCT/LDH composites. Notably, the BCT/LDH composites exhibited remarkable performance in the degradation of hazardous materials (methyl orange and isoniazid), superior to that of the individual components, reference P25, and P25/LDH under visible-light irradiation. Moreover, the BCT/LDH composite containing 30 wt% of BCT displayed the highest photocatalytic performance among the synthesized photocatalysts and also exhibited high stability during recycling tests with no obvious change in the activity. The superior photodegradation activity of the BCT/LDH composites was primarily attributed to efficient transfer and separation of the photoinduced charge carriers, resulting from the intimate contact interfaces between LDH and BCT. This approach represents a promising route for the rational design of highly efficient and visible-light-active LDH-based composite photocatalysts for application in energy harvesting and environmental protection.

g-C3N4/NiAl-LDH 2D/2D Hybrid Heterojunction for High-Performance Photocatalytic Reduction of CO2 into Renewable Fuels.

2D/2D interface heterostructures of g-C3N4 and NiAl-LDH are synthesized utilizing strong electrostatic interactions between positively charged 2D NiAl-LDH sheets and negatively charged 2D g-C3N4 nanosheets. This new 2D/2D interface heterojunction showed remarkable performance for photocatalytic CO2 reduction to produce renewable fuels such as CO and H2 under visible-light irradiation, far superior to that of either single phase g-C3N4 or NiAl-LDH nanosheets. The enhancement of photocatalytic activity could be attributed mainly to the excellent interfacial contact at the heterojunction of g-C3N4/NiAl-LDH, which subsequently results in suppressed recombination, and improved transfer and separation of photogenerated charge carriers. In addition, the optimal g-C3N4/NiAl-LDH nanocomposite possessed high photostability after successive experimental runs with no obvious change in the production of CO from CO2 reduction. Our findings regarding the design, fabrication and photophysical properties of 2D/2D heterostructure systems may find use in other photocatalytic applications including H2 production and water purification.

Synthesis of Cr and La-codoped SrTiO3 nanoparticles for enhanced photocatalytic performance under sunlight irradiation.

In this study, we report a facile polymeric citrate strategy for the synthesis of Cr,La-codoped SrTiO3 nanoparticles. The synthesized samples were well characterized by various analytical techniques. The UV-vis DRS studies reveal that the absorption edge shifts towards the visible light region after doping with Cr, which is highly beneficial for absorbing the visible light in the solar spectrum. More attractively, codoping with La exhibits greatly enhanced photocatalytic activity for the degradation of Rhodamine B under sunlight irradiation. The optimum photocatalytic activity at 1 atom% of Cr,La-codoped SrTiO3 nanoparticles is almost 6 times higher than that of pure SrTiO3 nanoparticles and 3 times higher than that of Cr-doped SrTiO3 nanoparticles. The high photocatalytic performance in the present photocatalytic system is due to codoping with La, which acts as a most effective donor for stabilizing Cr(3+) in Cr,La-codoped SrTiO3 nanoparticles. More importantly, the synthesized photocatalysts possess high reusability. A proposed mechanism for the enhanced photocatalytic activity of Cr,La-codoped SrTiO3 nanoparticles was also investigated by trapping experiments. Therefore, our results not only demonstrate the highly efficient visible light photocatalytic activity of the Cr,La-codoped SrTiO3 photocatalyst, but also enlighten the codoping strategy in the design and development of advanced photocatalytic materials for energy and environmental applications.

Synthesis of novel and stable g-C3N4/N-doped SrTiO3 hybrid nanocomposites with improved photocurrent and photocatalytic activity under visible light irradiation.

Hybrid nanocomposites based on N-doped SrTiO3 nanoparticles wrapped in g-C3N4 nanosheets were successfully prepared by a facile and reproducible polymeric citrate and thermal exfoliation method. The results clearly indicated that the N-doped SrTiO3 nanoparticles are successfully wrapped in layers of the g-C3N4 nanosheets. The g-C3N4/N-doped SrTiO3 nanocomposites showed absorption edges at longer wavelengths compared with the pure g-C3N4 as well as N-doped SrTiO3. The hybrid nanocomposites exhibit an improved photocurrent response and photocatalytic activity under visible light irradiation. Interestingly, the hybrid nanocomposite possesses high photostability and reusability. Based on experimental results, the possible mechanism for prolonged lifetime of the photoinduced charge carrier was also discussed. The high performance of the g-C3N4/N-doped SrTiO3 photocatalysts is due to the synergic effect at the interface of g-C3N4 and N-doped SrTiO3 hetero/nanojunction including the high separation efficiency of the charge carrier, band energy matching and the suppressed recombination rate. Therefore, the hybrid photocatalyst could be of potential interest for water splitting and environmental remediation under natural sunlight.

Cost-effective and eco-friendly synthesis of novel and stable N-doped ZnO/g-C3N4 core-shell nanoplates with excellent visible-light responsive photocatalysis.

N-doped ZnO/g-C3N4 hybrid core-shell nanoplates have been successfully prepared via a facile, cost-effective and eco-friendly ultrasonic dispersion method for the first time. HRTEM studies confirm the formation of the N-doped ZnO/g-C3N4 hybrid core-shell nanoplates with an average diameter of 50 nm and the g-C3N4 shell thickness can be tuned by varying the content of loaded g-C3N4. The direct contact of the N-doped ZnO surface and g-C3N4 shell without any adhesive interlayer introduced a new carbon energy level in the N-doped ZnO band gap and thereby effectively lowered the band gap energy. Consequently, the as-prepared hybrid core-shell nanoplates showed a greatly enhanced visible-light photocatalysis for the degradation of Rhodamine B compare to that of pure N-doped ZnO surface and g-C3N4. Based on the experimental results, a proposed mechanism for the N-doped ZnO/g-C3N4 photocatalyst was discussed. Interestingly, the hybrid core-shell nanoplates possess high photostability. The improved photocatalytic performance is due to a synergistic effect at the interface of the N-doped ZnO and g-C3N4 including large surface-exposure area, energy band structure and enhanced charge-separation properties. Significantly, the enhanced performance also demonstrates the importance of evaluating new core-shell composite photocatalysts with g-C3N4 as shell material.