Heterostructural Ag3PO4/UiO-66 composite for highly efficient visible-light photocatalysts with long-term stability

Covalently anchoring silver nanoclusters Ag44 on modified UiO-66-NH2 with Bi2S3 nanorods and MoS2 nanoparticles for exceptional solar wastewater treatment activity

For the first time, covalently anchoring size selected silver nanoclusters [Ag44(MNBA)30] on the Bi2S3@UiO-66-NH2 and MoS2@UiO-66-NH2 heterojunctions were constructed as novel photocatalysts for photodegradation of methylene blue (MB) dye. The anchoring of Ag44 on MoS2@UiO-66-NH2 and Bi2S3@UiO-66-NH2 heterojunctions extended the light absorption of UiO-66-NH2 to the visible region and improved the transfer and separation of photogenerated charge carriers through the heterojunctions with a unique band gap structure. The UV-Vis-NIR diffuse reflectance spectroscopic analysis confirmed that the optical absorption properties of the UiO-66-NH2 were shifted from the UV region at 379 nm to the visible region at ~ 705 nm after its doping with Bi2S3 nanorods and Ag44 nanoclusters (Bi2S3@UiO-66-NH-S-Ag44). The prepared Bi2S3@UiO-66-NH-S-Ag44 and MoS2@UiO-66-NH-S-Ag44 photocatalysts exhibited exceptional photocatalytic activity for visible light degradation of MB dye. The photocatalysts exhibited complete decolorization of the MB solution (50 ppm) within 90 and 120 min stirring under visible light irradiation, respectively. The supper photocatalytic performance and recycling efficiency of the prepared photocatalysts attributed to the covalent anchoring of the ultra-small silver clusters (Ag44) on the heterojunctions surface. The X-ray photoelectron spectroscopic analysis confirmed the charge of the silver clusters is zero. The disappearance of the N-H bending vibration peak of primary amines in the FTIR analysis of Bi2S3@UiO-66-NH-S-Ag44 confirmed the covalent anchoring of the protected silver nanoclusters on the UiO-66-NH2 surface via the condensation reaction. The Bi2S3@UiO-66-NH-S-Ag44 catalyst exhibited excellent recyclability efficiency more than five cycles without significant loss in activity, indicating their good potential for industrial applications. The texture properties, crystallinity, phase composition, particle size, and structural morphology of the prepared photocatalysts were investigated using adsorption-desorption N2 isotherms, X-ray diffraction (XRD), HR-TEM, and FE-SEM, respectively.

Hetero-Interfaces on Cu Electrode for Enhanced Electrochemical Conversion of CO2 to Multi-Carbon Products

Electrochemical CO₂ reduction reaction (CO₂RR) to multi-carbon products would simultaneously reduce CO₂ emission and produce high-value chemicals. Herein, we report Cu electrodes modified by metal-organic framework (MOF) exhibiting enhanced electrocatalytic performance to convert CO₂ into ethylene and ethanol. The Zr-based MOF, UiO-66 would in situ transform into amorphous ZrO_x nanoparticles (a-ZrO_x), constructing a-ZrO_x/Cu hetero-interface as a dual-site catalyst. The Faradaic efficiency of multi-carbon (C2+) products for optimal UiO-66-coated Cu (0.5-UiO/Cu) electrode reaches a high value of 74% at - 1.05 V versus RHE. The intrinsic activity for C2+ products on 0.5-UiO/Cu electrode is about two times higher than that of Cu foil. In situ surface-enhanced Raman spectra demonstrate that UiO-66-derived a-ZrO_x coating can promote the stabilization of atop-bound CO* intermediates on Cu surface during CO₂ electrolysis, leading to increased CO* coverage and facilitating the C-C coupling process. The present study gives new insights into tailoring the adsorption configurations of CO₂RR intermediate by designing dual-site electrocatalysts with hetero-interfaces.

Novel MOF-Based Photocatalyst AgBr/AgCl@ZIF-8 with Enhanced Photocatalytic Degradation and Antibacterial Properties

A novel visible light-driven AgBr/AgCl@ZIF-8 catalyst was synthesized by a simple and rapid method. The composition and structure of the photocatalyst were characterized by XRD, SEM, UV-DRS, and XPS. It could be observed that the 2-methylimidazole zinc salt (ZIF-8) exhibited the rhombic dodecahedron morphology with the AgCl and AgBr particles evenly distributed around it. The composite photocatalyst AgBr/AgCl@ZIF-8 showed good photocatalytic degradation and antibacterial properties. The degradation rate of RhB solution was 98%, with 60 min of irradiation of visible light, and almost all P. aeruginosaudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli) were inactivated under the irradiation of 90 min. In addition, the prepared catalyst had excellent stability and reusability. Based on the free radical capture experiment, ·O₂⁻ and h⁺ were believed to be the main active substances, and possible photocatalytic degradation and sterilization mechanisms of AgBr/AgCl@ZIF-8 were proposed.

Simplified creation of polyester fabric supported Fe-based MOFs by an industrialized dyeing process: Conditions optimization, photocatalytics activity and polyvinyl alcohol removal

MIL-53(Fe) was successfully prepared and deposited on the surface carboxylated polyester (PET) fiber by an optimized conventional solvothermal or industrialized high temperature pressure exhaustion (HTPE) process to develop a PET fiber supported MIL-53(Fe) photocatalyst (MIL-Fe@PET) for the degradation of polyvinyl alcohol (PVA) in water under light emitting diode (LED) visible irradiation. On the basis of several characterizations, MIL-Fe@PET was tested for the photocalytic ability and degradation mechanism. It was found that temperature elevation significantly enhanced the formation and deposition of MIL-53(Fe) with better photocatalytic activity. However, higher temperature than 130°C was not in favor of its photocatalytic activity. Increasing the number of surface carboxyl groups of the modified PET fiber could cause a liner improvement in MIL-53(Fe) loading content and photocatalytic ability. High visible irradiation intensity also dramatically increased photocatalytic ability and PVA degradation efficiency of MIL-Fe@PET. Na₂S₂O₈ was used to replace H₂O₂ as electron acceptor for further promoting PVA degradation in this system. MIL-Fe@PET prepared by HTPE process showed higher MIL-53(Fe) loading content and slightly lower PVA degradation efficiency than that prepared by solvothermal process at the same conditions. These findings provided a practical strategy for the large-scale production of the supported MIL-53(Fe) as a photocatalyst in the future.

Novel visible-light-driven SrCoO3/Ag3PO4 heterojunction with enhanced photocatalytic performance for tetracycline degradation

The semiconductor photocatalytic technology has been considerably studied due to its excellent catalytic performance in water pollution control. Herein, in this study, novel SrCoO₃/Ag₃PO₄ composite materials with different SrCoO₃ content were synthesized via a simple hydrothermal synthesis method. The characteristics of the as-prepared samples were detected through SEM/HRTEM, XRD, UV-vis DRS, PL, ESR, FT-IR, and XPS techniques, and then, the photocatalytic performance of SrCoO₃/Ag₃PO₄ toward the degradation of tetracycline was investigated. When the mass ratio of SrCoO₃ and Ag₃PO₄ in the composite was 1:1.5, the degradation rate constant of tetracycline in SrCoO₃/Ag₃PO₄ (1:1.5) system is 0.0102 min^-1, which is 1.7 times that of the Ag₃PO₄, and 3.78 times that of the SrCoO₃. In addition, reactive species were also analyzed through the free radical trapping experiment and DMPO spin-trapping ESR spectra analysis, showing that OH^•, h⁺, and O₂^•-participated in the catalytic degradation process of tetracycline to varying degrees. Finally, the photocatalytic mechanism of SrCoO₃/Ag₃PO₄ was also proposed.

The covalent Coordination-driven Bi2S3@NH2-MIL-125(Ti)-SH heterojunction with boosting photocatalytic CO2 reduction and dye degradation performance

Herein, the optional and controllable growth of Bi₂S₃ onto NH₂-MIL-125 via covalent conjunction strategy was reported. The experimental results demonstrate that the obtained heterojunction exhibits boosting photocatalytic reduction CO₂ and organic dye degradation. The 18-Bi₂S₃@NH₂-MIL-125-SH displays the highest yield of 12.46 μmol g^-1h^-1 of CO, >13 times that of pure NH₂-MIL-125. Meanwhile, the reaction kinetic of 18-Bi₂S₃@NH₂-MIL-125-SH in the degradation of methylene blue is uppermost, which is 160 times than that of the commercial P25. The enhancement of photocatalytic performance could be ascribed to the covalent coordination-driven intimate interfacial interaction in n-scheme heterojunction. Meanwhile, the plausible mechanism was also investigated by UV-vis diffuse reflectance (UV-vis), photoluminescence (PL), electrochemical photocurrent, electron spin resonance (ESR) and electrochemical impedance spectroscopy (EIS).

Interfacial band bending induced charge-transfer regulation over Ag@ZIF-8@g-C3N4 to boost photocatalytic CO2 reduction into syngas

The use of the AZC-10 heterostructure enables excellent syngas production rates of 4076.4 μmol gcatalyst−1 h−1 and 3326.55 μmol gcatalyst−1 h−1 for CO and H2, respectively, much higher than other reported photocatalysts.

WO3/Ag2CO3 Mixed Photocatalyst with Enhanced Photocatalytic Activity for Organic Dye Degradation

The development of an efficient photocatalyst with superior activity under visible light has been regarded as a significant strategy for pollutant degradation and environmental remediation. Herein, a series of WO₃/Ag₂CO₃ mixed photocatalysts with different proportions were prepared by a simple mixing method and characterized by XRD, SEM, TEM, XPS, and DRS techniques. The photocatalytic performance of the WO₃/Ag₂CO₃ mixed photocatalyst was investigated by the degradation of rhodamine B (RhB) under visible light irradiation (λ > 400 nm). The photocatalytic efficiency of the mixed WO₃/Ag₂CO₃ photocatalyst was rapidly increased with the proportion of Ag₂CO₃ up to 5%. The degradation percentage of RhB by WO₃/Ag₂CO₃-5% reached 99.7% within 8 min. The pseudo-first-order reaction rate constant of WO₃/Ag₂CO₃-5% (0.9591 min^-1) was 118- and 14-fold higher than those of WO₃ (0.0081 min^-1) and Ag₂CO₃ (0.0663 min^-1). The catalytic activities of the mixed photocatalysts are not only higher than those of the WO₃ and Ag₂CO₃ but also higher than that of the WO₃/Ag₂CO₃ composite prepared by the precipitation method. The activity enhancement may be because of the easier separation of photogenerated electron-hole pairs. The photocatalytic mechanism was investigated by free radical capture performance and fluorescence measurement. It was found that light-induced holes (h⁺) was the major active species and superoxide radicals (·O₂ ^-) also played a certain role in photocatalytic degradation of RhB.

Structure, Photoluminescence Emissions, and Photocatalytic Activity of Ag2SeO3: A Joint Experimental and Theoretical Investigation

In this paper, we report the synthesis of silver selenite (Ag₂SeO₃) by different methods [sonochemistry, ultrasonic probe, coprecipitation, and microwave-assisted hydrothermal methods]. These microcrystals presented a structural long-range order as confirmed by X-ray diffraction (XRD) and Rietveld refinements and a structural short-range order as confirmed by Fourier transform infrared (FTIR) and Raman spectroscopies. X-ray photoelectron spectroscopy (XPS) provided information about the surface of the samples indicating that they were pure. The microcrystals presented different morphologies and sizes due to the synthesis method as observed by field emission scanning electron microscopy (FE-SEM). The optical properties of these microcrystals were evaluated by ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL) measurements. Thermal analysis confirmed the temperature stability of the as-synthetized samples. Further trapping experiments prove that the holes and hydroxyl radicals, to a minor extent, are responsible for the photocatalytic reactions. The experimental results are sustained by first-principles calculations, at the density functional theory (DFT) level, to decipher the structural parameters, electronic properties of the bulk, and surfaces of Ag₂SeO₃. By matching the experimental FE-SEM images and theoretical morphologies, we are capable of finding a correlation between the morphology and photocatalytic activity, along with photodegradation of the Rhodamine B dye under UV light, based on the different numbers of unsaturated superficial Ag and Se cations (local coordination, i.e., clusters) of each surface.

Bi2S3@NH2-UiO-66-S composites modulated by covalent interfacial reactions boost photodegradation and the oxidative coupling of primary amines

The Bi₂S₃@NH₂-UiO-66-S heterostructures have been synthesized via covalent interfacial reactions, exhibiting excellent performance in the photodegradation of methylene and the oxidative coupling of primary amines compared to reported photocatalysts.

Facile synthesis of a novel Ag3PO4/MIL-100(Fe) Z-scheme photocatalyst for enhancing tetracycline degradation under visible light

In this work, a novel visible light-driven heterostructure Ag₃PO₄/MIL-100(Fe) composite photocatalyst was successfully synthesized via facile chemical deposition method at room temperature. Especially when the mass ratio of Ag₃PO₄ was 20% of MIL-100(Fe) (APM-2), it displayed the best photocatalytic performance, for which the degradation rate of tetracycline (TC) in conventional environment was 6.8 times higher than that of bare MIL-100(Fe). In addition, the effects of the initial concentration and pH of the solution on the degradation of tetracycline were also studied, and the results showed that the degradation of tetracycline was more favorable in a weakly alkaline environment. The excellent performance of Ag₃PO₄/MIL-100(Fe) composites was attributed to the fact that on the basis of having adequate photocatalytic active sites, modifying MIL-100(Fe) with an appropriate amount of Ag₃PO₄ particles can more effectively separate photogenerated electron-hole pairs. Five cycles of experiments showed that APM-2 has good photostability. Lastly, it was proved through quenching experiments that •O₂^-, h⁺, and •OH all played corresponding roles in the degradation process, and a possible Z-scheme heterostructure photocatalytic degradation mechanism was proposed.

Characteristics of hydrogen production by photocatalytic water splitting using liquid phase plasma over Ag-doped TiO2 photocatalysts

Hydrogen production from water was investigated by applying liquid plasma (LPP) to photocatalytic splitting of water. The optical properties of LPP due to water emission were also evaluated. The correlation between the optical properties of plasma and the formation of active species in water was investigated with the photocatalytic activity of hydrogen production. TiO₂ was also doped with Ag to evaluate the effect of enhancing photocatalytic activity. The photocatalytic activity was evaluated by the rate of hydrogen production, and the effect of hydrogen formation was also investigated by injecting methanol as an additive. As a result of examining the luminescence properties of LPP, it showed high luminescence in the 309 nm UV region and the 656 nm visible region. The hydrogen doping rate was increased in the Ag-doped TiO₂ photocatalyst. Ag-doped TiO₂ has wider light absorption into the visible region and narrower band gap. Due to these properties, the rate of hydrogen generation is superior to TiO₂ photocatalysts. The photochemical reaction with LPP and photocatalyst in aqueous solution with CH₃OH showed a significant increase in hydrogen production rate. The increase in hydrogen production by injection of additives is because the optical properties of generating OH radicals are improved and CH₃OH is decomposed to act as an electron donor to improve hydrogen production.

Tetrahedral UMOFNs/Ag3PO4 Core-Shell Photocatalysts for Enhanced Photocatalytic Activity under Visible Light

A new visible-light-responsive tetrahedral ultrathin metal-organic framework nanosheet (UMOFNs)/Ag₃PO₄ composite photocatalyst with a core-shell structure was readily synthesized by sonication in an organic solvent. Characterization methods for the photocatalyst included X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectroscopy. The XRD patterns of the composite photocatalyst before and after visible-light irradiation demonstrated that trace amounts of Ag ions in the composite photocatalyst easily transformed into Ag nanoparticles, which play a role in promoting charge separation at the interface of a heterojunction. The UMOFNs/Ag₃PO₄ composite photocatalyst showed higher photocatalytic activity for the photodegradation of 2-chlorophenol (2-CP) under visible-light irradiation (>420 nm) than Ag₃PO₄. The complete degradation of 2-CP was achieved in 7 min using the tetrahedral UMOFNs/Ag₃PO₄ core-shell photocatalyst, and the apparent reaction rate was approximately 26 times higher than that of pure Ag₃PO₄. Further, a scavenger experiment showed h⁺ and O₂ ^•- were the major reactive species involved in the photocatalytic reaction system. This enhanced photocatalytic activity results from the efficient separation of photoinduced electron-hole pairs and the increase of interface area between Ag₃PO₄, UMOFNs, and the Ag nanoparticles.