A magnetically reusable Ce-MOF/GO/Fe3O4 composite for effective photocatalytic degradation of chlortetracycline.

Herein, we report a novel 1/GO/Fe3O4 photocatalyst, comprising Ce(BTB)(H2O) (MOF-1, H3BTB = 1,3,5-benzenetrisbenzoic acid), graphene oxide (GO), and iron oxide (Fe3O4) for photocatalytic degradation of chlortetracycline (CTC). This design enables the effective transfer of electrons from the MOF to GO, thereby reducing the photoelectron-hole recombination rate. Therefore, the optimized 1/GO/Fe3O4 photocatalyst with H2O2 shows the highest photocatalytic activity toward CTC. The kinetic constant is 5.4 times that in the system of MOF-1 and hydrogen peroxide, which usually acted as efficient electron acceptors to improve the photocatalytic performance of MOFs. More importantly, light absorption is extended from the ultraviolet to the visible region. Furthermore, 1/GO/Fe3O4 can be quickly recycled under an applied magnetic field and displays outstanding stability and reusability. According to the radical trapping experiments and electron paramagnetic resonance results, hydroxyl radicals, superoxide radicals, and holes all contribute to excellent photocatalytic activity. The possible catalytic mechanism of 1/GO/Fe3O4 is tentatively proposed. This work aims to explore the synergistic effect between metal-organic frameworks (MOFs) and GO, and provide a theoretical basis for MOF-based composites to remove antibiotic contaminants in the environment.

Theoretical prediction on the stability, elastic, electronic and optical properties of MAB-phase M4AlB4 compounds (M = Cr, Mo, W).

This research employs first-principles calculations to address the challenges presented by processing complexity and low damage tolerance in transition metal borides. The study focuses on designing and investigating MAB phase compounds of M4AlB4 (M = Cr, Mo, W). We conduct a comprehensive assessment of the stability, phononic, electronic, elastic, and optical properties of Cr4AlB4, Mo4AlB4, and W4AlB4. The calculated results reveal formation enthalpies of -0.516, -0.490, and -0.336 eV per atom for Cr4AlB4, Mo4AlB4, and W4AlB4, respectively. Notably, W4AlB4 emerges as a promising precursor material for MABene synthesis, demonstrating exceptional thermal shock resistance. The dielectric constants ε1(0) were determined as 126.466, 80.277, and 136.267 for Cr4AlB4, Mo4AlB4, and W4AlB4, respectively. Significantly, W4AlB4 exhibits remarkably high reflectivity (>80%) within the wavelength range of 19.84-23.6 nm, making it an ideal candidate for extreme ultraviolet (EUV) reflective coatings. The insights gleaned from this study provide a strong research framework and theoretical guidance for advancing the synthesis of innovative MAB-phase compounds.

S-scheme MOF-on-MOF heterojunctions for enhanced photo-Fenton Cr(VI) reduction and antibacterial effects.

The photocatalytic efficiency is commonly restrained by inferior charge separation rate. Herein, the S-scheme MIL-100(Fe)/NH2-MIL-125(Ti) (MN) photo-Fenton catalyst with the built-in electric field (BEF) was successfully constructed by a simple ball-milling technique. As a result, the MN-3 (the mass ratio of MIL-100(Fe) to NH2-MIL-125(Ti) was 3) composite presented the best visible-light-induced photocatalytic ability, in contrast to pure MIL-100(Fe) and NH2-MIL-125(Ti). The reduction efficiency of Cr(VI) almost reached 100% within 35 min of illumination. Moreover, the MN-3 heterojunction also exhibited the highest antibacterial activity, and about 100% E. coli and more than 90% S. aureus were killed within 60 min of illumination. In photo-Fenton system, In the photo-Fenton system, e-, O2•- and Fe2+ played vital roles for Cr(VI) reduction, and •OH, h+ and O2•- and 1O2 were responsible for sterilization. Additionally, 5 cyclic tests and relevant characterizations confirmed the excellent repeatability and stability of the composite. Also, the S-scheme charge transfer process was put forward. This work offers a novel idea for establishing the MOF-on-MOF photo-Fenton catalyst for high-efficiency environmental mitigation.

In Situ Synthesis of Bi2MoO6/Bi2SiO5 Heterojunction for Efficient Degrading of Persistent Pollutants.

Photocatalytic degradation is an environmentally friendly way to eliminate environmental pollution. Exploring a photocatalyst with high efficiency is essential. In the present study, we fabricated a Bi2MoO6/Bi2SiO5 heterojunction (BMOS) with intimate interfaces via a facile in situ synthesis method. The BMOS had much better photocatalytic performance than pure Bi2MoO6 and Bi2SiO5. The sample of BMOS-3 (3:1 molar ratio of Mo:Si) had the highest removal efficiency by the degradation of Rhodamine B (RhB) up to 75% and tetracycline (TC) up to 62% within 180 min. The increase in photocatalytic activity can be attributed to constructing high-energy electron orbitals in Bi2MoO6 to form a type II heterojunction, which increases the separation efficiencies of photogenerated carriers and transfer between the interface of Bi2MoO6 and Bi2SiO5. Moreover, electron spin resonance analysis and trapping experiments showed that the main active species were h+ and •O2- during photodegradation. BMOS-3 maintained a stable degradation capacity of 65% (RhB) and 49% (TC) after three stability experiments. This work offers a rational strategy to build Bi-based type II heterojunctions for the efficient photodegradation of persistent pollutants.

Ferric-ellagate complex: A promising multifunctional photocatalyst.

The semiconductors have exhibited great potential in the field of photocatalytic energy production, environmental remediation and bactericidal. Nevertheless, those inorganic semiconductors are still restricted in commercial application due to the drawbacks of easy agglomeration and low solar energy conversion efficiency. Herein, ellagic acid (EA) based metal-organic complexes (MOCs) were synthesized through a facile stirring process at room temperature with Fe3+, Bi3+ and Ce3+ as the metal center. The EA-Fe photocatalyst exhibited superior photocatalytic activity toward Cr(VI) reduction, where Cr(VI) were completely removed within 20 min. Meanwhile, EA-Fe also displayed good photocatalytic degradation of organic contaminants and photocatalytic bactericidal performance. The photodegradation rates of TC and RhB by EA-Fe were 15 and 5 times that by bare EA, respectively. Moreover, EA-Fe was capable of effectively eliminating both E. coli and S. aureus bacteria. It was found that EA-Fe was capable of generating superoxide radicals, which could participate in the reduction of heavy metals, degradation of organic contaminants and inactivation of bacteria. A photocatalysis-self-Fenton system could be established by EA-Fe solely. This work would provide a new insight for designing multifunctional MOCs with high photocatalytic efficiency.

Metal ion endogenous cycles of CoFe2O4-x induced boosted photocatalytic/PMS degradation toward polycyclic aromatic hydrocarbons.

The rational design of photocatalytic nanomaterials with unique structures is critical for remediating environmental problems and thus reducing ecological risks. In this work, we employed H2 temperature-programmed reduction to modify MFe2O4 (M = Co, Cu, and Zn) photocatalysts for obtaining additional oxygen vacancies. After activation of PMS, naphthalene and phenanthrene degradation rates in the soil phase were increased by 3.24-fold and 1.39-fold, respectively, and 1.38-fold for naphthalene in the aqueous phase by H-CoFe2O4-x. The extraordinary photocatalytic activity is attributed to the oxygen vacancies on the H-CoFe2O4-x surface, which promote electron transfer and thus enhance the redox cycle from Co(III)/Fe(III) to Co(II)/Fe(II). In addition, oxygen vacancies are used as electron traps to hinder the recombination of photogenerated carriers and accelerate the generation of hydroxyl and superoxide radicals. Quenching tests showed that the addition of p-benzoquinone resulted in the greatest decrease in the degradation rate of naphthalene (inhibition of about 85.5%), demonstrating that O2˙- radicals are the main active species in the photocatalytic degradation of naphthalene. H-CoFe2O4-x showed improved degradation performance in synergy with PMS (82.0%, kapp = 0.00714 min-1) while maintaining excellent stability and reusability. Hence, this work provides a promising approach for the design of efficient photocatalysts to degrade persistent organic pollutants in soil and aqueous environments.

Preparation of novel diperylene-cored polyimide photocatalyst with broad-spectra response and high stability.

A novel polyimide (PI) with broad-spectra response, high photocatalytic activity and stability under super acidic conditions (pH = 0) was synthesized via polymerizing method. Two types of perylene-cored materials (PDIAN and PTCDA) with anhydride and diamine respectively, were applied as precursors for PI polymerization. The as-prepared PI was optimized at 1:1 initial molar ratio of PDIAN to PTCDA. Using common PI (synthesized from melamine and pyromellitic dianhydride) as comparison, the Cr(VI) reduction rate was boosted from 25.4% to 96.6% within 120 min light irradiation. The corresponding rate constant by PI(PDIAN/PTCDA) was estimated to be ca. 11.7 times relative to that by common PI. The boosted performance was ascribed to the strong π-π conjugation from diperylene cores, which can decrease the photoluminescence intensity and electrochemical impedance, so as to promote the separation and transfer of photogenerated electron-hole pairs. In addition, the optimized PI(PDIAN/PTCDA) displayed wide-spectra response, which can still work under 730 nm light. The influencing factors toward Cr(VI) reduction were also clarified to be beneficial at lower pH and increased concentration of hole scavenger. After five cycles at pH 0, the PI still maintained excellent redox activity and structural stability.

PDINH bridged NH2-UiO-66(Zr) Z-scheme heterojunction for promoted photocatalytic Cr(VI) reduction and antibacterial activity.

Z-scheme mechanism was a promising approach to considerably enhance photocatalytic activity. In this work, the PDINH/NH2-UiO-66(Zr) (PNU) heterojunctions were made using a facile ball-milling method. As expect, the optimum PNU-1 composite acted as highly active photocatalyst with 97% Cr(VI) to be reduced within 60 min of LED light illumination. Moreover, the antibacterial rate almost reached 100% for E. coli and S. aureus in 4 h, which was more conspicuous than the others. The wider light absorption range, promoted charge separation because of Z-scheme mechanism and efficient generation of reactive 1O2, •O2-, and •OH contributed greatly to the enhanced photocatalytic activity. Meanwhile, the superior stability and repeatability of the composites were also demonstrated by five cyclic experiments and related physicochemical characterizations. Therefore, this work provides a novel insight for designing high-efficiency Z-scheme heterostructures between MOFs and organic PDINH for wastewater remediation.

Heterostructured V-Doped Ni2 P/Ni12 P5 Electrocatalysts for Hydrogen Evolution in Anion Exchange Membrane Water Electrolyzers.

Regulating the electronic structure and intrinsic activity of catalysts' active sites with optimal hydrogen intermediates adsorption is crucial to enhancing the hydrogen evolution reaction (HER) in alkaline media. Herein, a heterostructured V-doped Ni2 P/Ni12 P5 (V-Ni2 P/Ni12 P5 ) electrocatalyst is  fabricated through a hydrothermal treatment and controllable phosphidation process. In comparison with pure-phase V-Ni2 P, in/ex situ characterizations and theoretical calculations reveal a redistribution of electrons and active sites in V-Ni2 P/Ni12 P5 due to the V doping and heterointerfaces effect. The strong coupling between Ni2 P and Ni12 P5 at the interface leads to an increased electron density at interfacial Ni sites while depleting at P sites, with V-doping further promoting the electron accumulation at Ni sites. This is accompanied by the change of active sites from the anionic P sites to the interfacial Ni-V bridge sites in V-Ni2 P/Ni12 P5 . Benefiting from the interface electronic structure, increased number of active sites, and optimized H-adsorption energy, the V-Ni2 P/Ni12 P5 exhibits an overpotential of 62 mV to deliver 10 mA cm-2 and excellent long-term stability for HER. The V-Ni2 P/Ni12 P5 catalyst is applied for anion exchange membrane water electrolysis to deliver superior performance with a current density of 500 mA cm-2 at a cell voltage of 1.79 V and excellent durability.

Perylene diimide growth on both sides of carbon nanotubes for remarkably boosted photocatalytic degradation of diclofenac.

Perylene diimide and its derivatives are promising photocatalysts for clean and efficient production, but their practical application in the field of photocatalysis is still limited by the rapid photogenerated charge recombination. In this work, the confined photocatalysts were synthesized by using a gas-phase self-assembly method and comparing the morphology and photocatalytic properties of different photocatalysts after the confinement of carbon nanotubes. The confinement effect of carbon nanotubes acts to stabilize perylene diimide. Electrostatic interaction formed by a wide range of dispersion forces is dominant in the process of stabilization. Benefitting from the three-dimensional electron transfer pathway formed by the conjugation of perylene diimide with a large number of π electrons to the carbon nanotubes plane, the confined photocatalyst shows the pseudo-first-order kinetic constant k of 1.106 h-1 for the photocatalytic degradation of diclofenac under light, which is 6.11 times higher than that of perylene diimide. The electron transfer created an internal electric field at the interface from carbon nanotubes to perylene diimide, which greatly accelerated the separation of photogenerated electron-hole pairs and improved the photocatalytic activity. This study further expands the applicability of perylene diimide in the field of photocatalysis and provides a new approach for water environment treatment.

High-performance photocatalytic decomposition of PFOA by BiOX/TiO2 heterojunctions: Self-induced inner electric fields and band alignment.

BiOX (X = Cl, Br and I) and BiOX/TiO2 photocatalysts were prepared by a facile hydrothermal approach. The BiOX/TiO2 heterojunctions demonstrated significantly enhanced efficiency for photocatalytic decomposition of perfluorooctanoic acid (PFOA) compared with sole BiOX or TiO2. PFOA (10 mg L1) was completely degraded by BiOCl(Br)/TiO2 in 8 h. Moreover, BiOCl/TiO2 attained deep decomposition of PFOA with a high defluorination ratio of 82%. The p-n heterojunctions between BiOX and TiO2 were confirmed by a series of characterizations. The photo-induced holes would migrate from the valance band (VB) of TiO2 to BiOX, driven by the built-in electric field (BIEF) near the interfaces of p-n heterojunctions, the inner electric fields (IEF) in BiOX and the higher VB position of BiOX. The X-ray diffraction (XRD) and TEM characterizations indicated that TiO2 combined with BiOX along the [110] facet, which facilitated photo-induced electron transfer in the [001] direction, thus benefiting PFOA decomposition.

Recent advances in photocatalytic nitrogen fixation and beyond.

The traditional synthesis of ammonia is an industrial process with high energy consumption that is not environmentally friendly; thus, it is urgent to develop cost-effective approaches to synthesize ammonia under ambient conditions. In recent years, the photochemical synthesis of ammonia has become a hot research frontier. In this mini review, we summarize the recent advances in materials sciences for photocatalytic nitrogen fixation. Beyond nitrogen fixation, we talk about an alternative for artificial ammonia synthesis and coupling reactions with other reactions for the synthesis of other high-value chemicals. The results and findings of this review will help the development of ammonia synthesis and the synthesis of other high-value chemicals.

Fertiliser recovery from source-separated urine via membrane bioreactor and heat localized solar evaporation.

Urine with its abundant macronutrients (N-P-K) is an ideal resource for the production of fertiliser. However, the odor and pathogens in the raw urine must be removed to meet the public acceptance of urine collection systems and to enable its safe reuse as a fertiliser. In this work, real urine was collected and treated through a pilot-scale gravity-driven membrane bioreactor (GDMBR) to remove the malodorous organics and to nitrify almost 50% of the ammonia into nitrate. The stablised urine was subsequently distilled via low-cost heat localized solar evaporation (HLSE) to produce a non-odorous solid fertiliser. The developed HLSE with a small footprint can attract bulk solution into a vertical insulated space and quickly heat it up to 68 °C within 1 h. The HLSE process had vapour flux at 1.3 kg m-2 h-1 as well as high solar to vapour conversion efficiency at 87%. Based on the EDX mapping and XRD analysis, the generated crystals are mainly NaNO3, NH4Cl, NaCl, NH4H2PO4 and K2HPO4, which are ideal nutrients for vegetation. In this study, the produced urine-derived fertilisers have a better performance on the growth of the leafy basil than the all-purpose commercial fertilisers. Generally, the GDMBR-HLSE is a promising cost-effective and green technology for nutrients recovery from urine.

Defect engineering of oxide perovskites for catalysis and energy storage: synthesis of chemistry and materials science.

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

A facile oxygen vacancy and bandgap control of Bi(OH)SO4·H2O for achieving enhanced photocatalytic remediation.

The development of highly efficient photocatalysts is crucial for the remediation of organic pollutants. Herein, we reported a facile synthesis of oxygen vacancy rich Bi(OH)SO4·H2O photocatalyst by the control of precursor. The samples were characterized by XRD, scanning electron microscope, electron paramagnetic resonance, X-ray photoelectron spectroscopy etc. With more oxygen vacancies introduced, the photocatalytic activity on the degradation of RhB and tetracycline was significantly boosted. Density functional theory calculation was used to further reveal the influence of oxygen vacancy on the band structure of Bi(OH)SO4·H2O. The results and finding of this work are helpful for the development of sustainable environmental protection.

Optimizing the Carbon Dioxide Reduction Pathway through Surface Modification by Halogenation.

Facilitating the charge separation of semiconductor photocatalysts to increase the photocatalytic CO2 reduction activity has become a great challenge for sustainable energy conversion. Herein, the surface halogen-modified defect-rich Bi2 WO6 nanosheets have been successfully prepared to address the aforementioned challenge. Importantly, the modification of surface with halogen atoms is beneficial for the adsorption and activation for CO2 molecules and charge separation. These properties have been analyzed by experimental and theoretical methods. DFT calculations revealed that the modification of the Bi2 WO6 surface with Br atoms can decrease the formation energy of the *COOH intermediate, which accelerates CO2 conversion. All halogen-modified defect-rich Bi2 WO6 nanosheets showed an enhanced photocatalytic CO2 reduction activity. Specifically, Br-Bi2 WO6 exhibited the best CO generation rate of 13.8 µmol g-1 h-1 , which is roughly 7.3 times as high as the unmodified defect-rich Bi2 WO6 (1.9 µmol g-1 h-1 ). Moreover, in the presence of a cocatalyst (cobalt phthalocyanine) and a sacrificial agent (triethanolamine), Br-Bi2 WO6 exhibited an even further improved CO generation rate of 187 µmol g-1 h-1 . This finding provides a new approach to optimize the CO2 reduction pathway of semiconductor photocatalysts, which is beneficial to develop highly efficient CO2 reduction photocatalysts.

Dominant Polar Surfaces of Colloidal II-VI Wurtzite Semiconductor Nanocrystals Enabled by Cation Exchange.

Polar surfaces of ionic crystals are of growing technological importance, with implications for the efficiency of photocatalysts, gas sensors, and electronic devices. The creation of ionic nanocrystals with high percentages of polar surfaces is an option for improving their efficiency in the aforementioned applications but is hard to accomplish because they are less thermodynamically stable and prone to vanish during the growth process. Herein, we develop a strategy that is capable of producing polar surface-dominated II-VI semiconductor nanocrystals, including ZnS and CdS, from copper sulfide hexagonal nanoplates through cation exchange reactions. The obtained wurtzite ZnS hexagonal nanoplates have dominant {002} polar surfaces, occupying up to 97.8% of all surfaces. Density functional theory calculations reveal the polar surfaces can be stabilized by a charge transfer of 0.25 eV/formula from the anion-terminated surface to the cation-terminated surface, which also explains the presence of polar surfaces in the initial Cu1.75S hexagonal nanoplates with cation deficiency prior to cation exchange reactions. Experimental results showed that the HER activity could be boosted by the surface polarization of polar surface-dominated ZnS hexagonal nanoplates. We anticipate this strategy is general and could be used with other systems to prepare nanocrystals with dominant polar surfaces. Furthermore, the availability of colloidal semiconductor nanocrystals with dominant polar surfaces produced through this strategy opens a new avenue for improving their efficiency in catalysis, photocatalysis, gas sensing, and other applications.