MoSe2-NiSe dual co-catalysts modified g-C3N4 for enhanced photocatalytic H2 generation

Enhanced visible light photocatalytic performance of carbon and oxygen co-doped carbon nitride with a three-dimensional structure: Performance and mechanism study

As a cost-effective photocatalyst, carbon nitride (g-C3N4) holds tremendous promise for addressing energy shortages and environmental pollution. However, its application is limited by disadvantages such as low specific surface area and easy recombination of photogenerated electron-hole pairs. This study introduces C and O co-doped g-C3N4 with a three-dimensional (3D) structure achieved through a straightforward one-step calcination process, demonstrating excellent photocatalytic activity of hydrogen production and oxytetracycline degradation, with superoxide radicals as the primary active species. We propose a plausible enhanced mechanism based on systematic characterizations and density functional theory calculations. The 3D structure confers a substantial specific surface area, enhancing both the adsorption area and active sites of catalysts while bolstering structural stability. Co-doping optimizes the band structure and electric conductivity of the catalyst, facilitating rapid migration of photogenerated charges. The synergistic effects of these enhancements significantly elevate the photocatalytic performance. This study presents a convenient and feasible method for the preparation of dual-regulated photocatalysts with outstanding performance.

Construction of intramolecular donor-acceptor type carbon nitride for photocatalytic hydrogen production

High-efficiency photocatalysts based on organic polymeric semiconductor are often limited by slow charge separation kinetics and sluggish redox reaction dynamics. Herein, the donor-acceptor conjugated polymeric carbon nitride (D/A-CN) was synthesized by grafting benzene ring and pyridine moiety into the backbone of CN through a flexible pyrolysis strategy. The D/A-CN shows a high photocatalytic H2 evolution rate of 4795 µmol·h-1·g-1, which is ≈6.08 times higher than that of pristine CN (787.5 µmol·h-1·g-1). Both experimental and theoretical results confirm that the robust internal electric field is established in the D/A-CN framework due to the enhanced molecular dipole, which apply a kinetic force to facilitate the separation and mobility of photogenerated carriers. Meanwhile, the deeper conduction band potential caused by the elevated orbital energy level of D/A-CN contributes to the enhanced reduction ability of photoinduced electron. Consequently, the faster carrier transfer kinetics and the stronger thermodynamic reduction driving force synergistically lead to efficient photocatalytic H2 production of D/A-CN. This work reinforces the comprehension of the structure-performance relationship of donor-acceptor structural photocatalysts and provides an insight for enhancing the photocatalytic activity of polymeric photocatalysts at the molecular level.

Synthesis of novel nanocomposite of g-C3N4 coated ZnO-MoS2 for energy storage and photocatalytic applications

Fabrication of heterostructures for energy storage and environmental remedial applications is an interesting subject of research that has been undertaken in this present investigation. The incorporation of g-C3N4 into ZnO:MoS2 heterojunction nanocomposite was accomplished by wet-chemical route and characterized by various techniques to ascertain its structure, morphology, and study its potential electro-optical characteristics. The g-C3N4@ZnO:MoS2 sample was investigated by x-ray diffraction (XRD) which reveals the co-existence of the ZnO, MoS2 and C3N4 phases linked to characteristic crystallographic planes in the spectrum, validating the formation of ternary nanocomposite. The XRD patterns of the pristine samples were also considered as reference to understand the structural evolution and phase transformations. Field emission scanning electron microscopy (FESEM) study states the formation of heterogeneous nanostructures having nanoparticles embedded on 2-D nanosheets like structures. Studies using energy dispersive spectroscopy (EDS) and elemental mapping show that all the elements that are linked to the above hybrid nanocomposite are present. Transmission electron microscopy (TEM) provided clear insights on the microstructure as we can identify the distribution of ZnO and MoS2 nanostructures on layered g-C3N4 nanosheets. The chemical composition and oxidation states of elements were elucidated by X-ray photoelectron spectroscopy (XPS) study, which added another layer of confirmation on the structural evolution of the ternary nanocomposite. Fourier transformed infrared (FTIR) study revealed the layered structure of sp2 hybridized bonding features of C and N in g-C3N4, besides Zn-O and Mo-S stretching vibrations. The nanocomposite demonstrated improved photodegradation efficacy and decomposed alizarin red and methylene blue dyes significantly with better stability and reusability. MoS2 as a co-catalyst acts as an electron acceptor/accelerator in the Z-scheme composite photocatalysis leading to improved photocatalytic efficiency. The resulting heterostructured material delivered a higher specific capacitance of 10.85 F/g with good capacitance retention. Electrochemical study revealed the energy storage capability of the hybrid system.

Photocarrier transfer induced by Nδ- → Wδ+ in tungsten trioxide/carbon nitride for dual-path production of hydrogen peroxide towards ciprofloxacin degradation

Photo self-Fenton catalyst is a promising candidate for solar energy conversion and environmental remediation. Here we reported a Tungsten trioxide/carbon nitride (WO3/CN) in which the surficial amino groups on CN are inserted into the WO3 matrix, forming coordinate covalently Nδ- → Wδ+ in construction of an intimate S-scheme heterojunction. The intimantance promotes the transfer of photocarriers under light irradiation. The nanohybrids produced hydrogen peroxide (H2O2) in a rate about 20 times of pristine CN. A dual-path architecture in which H2O2 are produced via hole-water oxidation and electron-oxygen reduction was poposed. It is founded that ciprofloxacin also involved in production of H2O2 by their deprotonation to superoxide anions, and holes and hydroxyl radicals effectively attack the weak sites in skeleton of ciprofloxacin. This work suggests a great significance of strategy in self-producing of H2O2 in utilizing solar energy and molecular oxygen for water, particularly the surface water decontamination.

Sulfur defect induced Cd0.3Zn0.7S in-situ anchoring on metal organic framework for enhanced photothermal catalytic CO2 reduction to prepare proportionally adjustable syngas

The rapid recombination of interfacial charges is considered to be the main obstacle limiting the photocatalytic CO2 reduction. Thus, it is a challenge to research an accurate and stable charge transfer control strategy. MIL-53 (Al)-S/Cd0.3Zn0.7S (MAS/CZS-0.3) photocatalysts with chemically bonded interfaces were constructed by in-situ electrostatic assembly of sulfur defect Cd0.3Zn0.7S (CZS-0.3) on the surface of MIL-53 (Al) (MAW), which enhanced interfacial coupling and accelerated electron transfer efficiency. An adjustable proportion of syngas (H2/CO) was prepared by photothermal catalytic CO2 reduction at micro-interface. and the optimal yield of CO (66.10 μmol∙g-1∙h-1) and H2 (71.0 μmol∙g-1∙h-1) was realized by the MAS/CZS-0.3 photocatalyst. The improved activity was due to the photogenerated electrons migrated from CZS-0.3 to the adsorption active sites of MAS, which strengthened the adsorption and activation of CO2 on MAS. The photothermal catalytic CO2 reduction to CO follows the pathway of CO2→*COOH → CO and CO2→*HCO3-→CO. This work provided a reference for the research, characterization, and application of in-situ anchoring of metal organic frameworks in photothermal catalytic CO2 reduction, and provided a green path for the supply of Syngas in industry.