Constructing a P2W18O626--Containing Hybrid Photocatalyst via Noncovalent Interactions for Enhanced H2 Production

Polyoxometalates (POMs) have gained significant research attention because of their excellent properties in photocatalytic (PC) hydrogen production. Exploring POM-based compounds for heterogeneous photocatalysis is an ongoing task. Here, we obtain a water-insoluble inorganic-organic hybrid compound, (P2W18O62)3(C12N3H10)6(C12N3H11)6·9.5H2O (P-PW), formed by Dawson-type POM P2W18O626- (P2W18) anions and protonated 2-(pyridin-4-yl)-1H-benzo[d]imidazole (PHB) cations via noncovalent interactions. In the presence of the sacrificial agent triethanolamine, P-PW exhibits a PC H2 generation rate of 0.418 mmol/g/h, surpassing that of P2W18 and PHB by 15 and 17 times, respectively. This enhancement in PC performance of P-PW can be attributed to its band structure change from the precursor compounds, leading to increased light absorption and therefore more efficient PC hydrogen production.

Excellent photocatalytic and antibacterial activities of bio-activated carbon decorated magnesium oxide nanoparticles

Green production of nanomaterials are restrict toxic substances and motivated the noxious free environment. Photocatalysis and antibacterial resistance are more promising and efficient fields for their chemical reductants and clean environment. Herein, we adopted a green and simple method for the biosynthesis of MgO NPs using Manilkara zapota as a bio source. Recently, the green synthesis of magnesium oxide nanoparticles has been a keen interest amongst researchers and scientists due to its simplicity eco-friendliness, non-toxic, inexpensive and potential to perform as an antibacterial agent. Activated carbon/Magnesium oxide (AC/MgO) photocatalyst was blended through a simple solution evaporation method. The surface electron microscopy (SEM) study reviles that AC/MgO had smooth and aggregated particles. The Fourier transform infrared (FT-IR) and x-ray diffraction (XRD) study confirms the structural formation and incorporation of nanoparticles into the AC matrix. Results confirmed the flourishing integration of MgO NPs over the activated carbon matrix. The electron movement and valency of AC/MgO photocatalyst reduced the bandgap and their findings were characterized by ultra visible diffuse reflectance spectroscopy (UV-DRS) and x-ray photoelectron spectroscopy (XPS). The blended AC/MgO photocatalyst was analyzed for photodegradation of Rhodamine- B (Rh-B) dye using a UV-visible spectrophotometer. The degradation study projects that the AC/MgO photocatalyst degrades (Rh-B) dye with 99% efficiency under simulated solar irradiation. This efficient degradation of (Rh-B) dye by AC/MgO photocatalyst is ascribed to the synergetic AC as catalytic support and adsorbent and MgO as photocatalyst. Finally, the photocatalytic material shows a better bactericidal effect in both gram-positive bacteria Escherichia coli-745 and gram-negative bacteria Staphylococcus aureus-9779. The AC/MgO photocatalyst is effectively used in bacteriocidal and photocatalytic removal of dyes and can be used for further development of water reuse and bio-medical fields. In addition, this research shows a viable method for synthesizing a cheap and effective AC/MgO for the photocatalytic destruction of organic pollutants.

Efficient visible-light-driven degradation of tetracycline by a 2D/2D rGO-Bi2WO6 heterostructure

Constructing heterostructures has been a simple yet effective strategy for improving the photocatalytic performance of individual semiconductor photocatalysts. However, the poor quality of the contacted interface coupled with the narrow and overlapping light absorption scope between heterocomponents limits potential improvement. Herein, a 2D/2D rGO-Bi₂WO₆ heterostructure with face-to-face compact contact interface and UV to NIR light absorption ability was synthesized to overcome the aforementioned limitations. The as-prepared 2 wt%-rGO-Bi₂WO₆ with a high contact interface quality exhibits the highest kinetic rate of (5.53 ± 0.75) × 10^-2 L mg^-1 min^-1 toward tetracycline (TC) degradation, which is 2.4 times higher than that of pristine Bi₂WO₆ and 2.1 times higher than that of the 2 wt%-rGO-Bi₂WO₆ composite with a poor interface quality. Moreover, approximately 30% of TC can be mineralized with a 2 wt%-rGO-Bi₂WO₆ presented system after 120 min. The subsequent Escherichia coli culture and liquid chromatography-mass spectrometry were employed to detect the biotoxicity variation of degradation intermediates and the possible transformation pathways of TC, respectively. Finally, the reactive species trapping results indicate that photogenerated holes and superoxide radical anions play dominant roles during the TC degradation process. This work provides a facile and effective method to fabricate an efficient heterojunction photocatalyst for pollutant degradation.

Phthalocyanine-sensitized evolution of hydrogen and degradation of organic pollutants using polyoxometalate photocatalysts

In this study, 2 (3), 9 (10), 16 (17), 23 (24)-tetrakis-(8-quinoline-oxy) phthalocyanine zinc(II) (ZnQPc) was prepared and then quaternized to obtain water soluble zinc phthalocyanine (ZnQPc⁴⁺). Then, ZnQPc⁴⁺ was used as a photosensitizer for a series of POM catalysts, including Dawson type K₆[α-P₂W₁₈O₆₂]·14H₂O (P₂W₁₈) and K₁₀[α-P₂W₁₇O₆₁]·20H₂O (P₂W₁₇) and Keggine type H₃PW₁₂O₄₀·xH₂O (PW₁₂). The Keggin type PW₁₂ showed higher efficiency with 18.2 μmol of H₂ evolution (turnover number (TON) = 14,550) for 6 h upon ZnQPc⁴⁺ sensitization in relation to two Dawson P₂W₁₇ and P₂W₁₈ in a visible light-driven water-soluble system with isopropanol and H₂PtCl₆·6H₂O. In addition, the complexes of ZnQPc⁴⁺ with a series of POM catalysts (P₂W₁₇, P₂W₁₈, and PW₁₂) were also used as photocatalysts for the degradation of methylene blue (MB) in water, and it was found that the complexes of ZnQPc⁴⁺ with P₂W₁₇ and PW₁₂ showed improved photocatalytic activity, and the degradation rates of MB reached 100% at a small dosage under natural pH and visible light. The high efficacy of POM catalysts for H₂ evolution and the degradation of MB were attributed to the sensitization of POMs by ZnQPc⁴⁺, which was enabled by the transfer of photogenerated electrons of ZnQPc⁴⁺ to the lowest unoccupied molecular orbital (LUMO) of POM.

Enhanced catalytic activity of α-FeOOH-rGO supported on active carbon fiber (ACF) for degradation of phenol and quinolone in the solar-Fenton system

A new heterogeneous solar-Fenton catalyst, α-FeOOH-reduced graphene oxide (rGO) supported on active carbon fiber (ACF), was synthesized via in situ electrophoretic deposition in a self-assembly process. Optimization of the components (electrophoretic deposition time of GO and Fe, GO dosages), the effect of pH and the catalysts stability were investigated systematically. The results indicated that rGO-α-FeOOH composite is formed during the ferrous-ion-induced self-assembly process on ACF. FeOOH-rGO/ACF displayed excellent catalytic activity for degrading phenol and quinoline under the solar-driven photo-Fenton process in a wide range of pH values (4.5-9.5) and possess good stability in neutral condition. The phenol oxidation process on this catalyst was described by a pseudo-first-order kinetics model. Both the ACF support and solar irradiation promoted greater H₂O₂ decomposition and produced more OH radicals, thus, significantly improving the catalytic capacity. The introduction of graphene improved the catalytic capacity of the catalyst under solar irradiation. The optimal electrophoretic deposition time of GO and the optimal Fe and initial GO content in deposition were 10 min, 9.8 wt% and 15.0 wt%, respectively. The degradation pathways of phenol and quinoline in the solar-driven photo-Fenton process were also elucidated.

Influence of different metal ions on the assembly, structures, and properties of two complexes based on the semi-rigid bis(pyridyl)-bis(amide) ligand and 4,4′-oxybis(benzoic acid)

Two transitional metal complexes, [Zn(oba)(3-bpcd)] n (1) and [Cd(oba)(3-bpcd)0.5] n (2) [H2oba= 4,4′-oxybis(benzoic acid), 3-bpcd=N,N′-bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide], have been hydrothermally synthesized and structurally characterized by elemental analyses, infrared spectra, powder X-ray diffraction, thermogravimetric and single-crystal X-ray diffraction. Complex 1 possesses a three-fold interpenetrating network based on layers with a 4-connected sql topology. Complex 2 is a layered framework constructed by the oba anions and 3-bpcd ligands, which represents a binodal (3,4)-connected {62.10}{6} topology. The adjacent layers of complex 2 are further linked by hydrogen bonding interactions to build a three-dimensional supramolecular architecture. The differences of metal ions in coordination modes show a significant effect on the final structures of the Zn(II)/Cd(II) complexes. The photocatalytic activities and the fluorescence sensing properties of complexes 1 and 2 were investigated.

Two polymolybdate-based complexes and their graphene composites with visible-light photo-responses

Two polymolybdate-based complexes with different band gaps show different visible-light photo-responses, and their graphene composite materials possess improved electrocatalytic activities for HER.