Hierarchical Sb2S3/ZnIn2S4 core–shell heterostructure for highly efficient photocatalytic hydrogen production and pollutant degradation

Enhanced photocatalytic performance of NiFe2O4/ZnIn2S4 p-n heterojunction for efficient degradation of tetracycline

The persistent release of tetracycline into the environment significantly endangers both ecosystems and human health. Zinc indium sulfide (ZnIn2S4) capable to degrade tetracycline pollutants under visible light irradiation has attracted extensive attentions and great effort has been devoted to augment its catalytic efficacy. In this work, we synthesized a p-n heterojunction, NiFe2O4/ZnIn2S4, to enhance the carrier migration rate and explained the intrinsic mechanism by density functional theory. When the heterojunction was formed, carriers traversed from the n-type NiFe2O4 to the p-type ZnIn2S4, instigating the emergence of a built-in electric field to facilitate the separation of carriers. 2 %-NiFe2O4/ZnIn2S4 exhibited excellent photocatalytic efficiency in tetracycline (TC) degradation and total organic carbon (TOC) removal. Compared to pure ZnIn2S4 and NiFe2O4, the TC degradation rates of 2 %-NiFe2O4/ZnIn2S4 were 2.0 times and 16.9 times higher, respectively. Additionally, 2 %-NiFe2O4/ZnIn2S4 had a saturation magnetization intensity of 3.05 emu/g, allowing for rapid recovery of the catalyst under a magnetic field. Superoxide radicals (O2-) and holes (h+) were the primary active species driving the degradation process. Furthermore, potential reaction pathways of tetracycline in this photocatalytic process were determined and bioconcentration factor and developmental toxicity of the intermediate products were accessed. This work held great potentials for wastewater treatment and provided a pathway for the development of magnetic recyclable photocatalysts.

Indium oxide-based Z-scheme hollow core-shell heterostructure with rich sulfur-vacancy for highly efficient light-driven splitting of water to produce clean energy

Crafting an inorganic semiconductor heterojunction with defect engineering and morphology modulation is a strategic approach to produce clean energy by the highly efficient light-driven splitting of water. In this paper, a novel Z-scheme sulfur-vacancy containing Zn3In2S6 (Vs-Zn3In2S6) nanosheets/In2O3 hollow hexagonal prisms heterostructrue (Vs-ZIS6INO) was firstly constructed by an oil bath method, in which Vs-Zn3In2S6 nanosheets grew on the surfaces of In2O3 hollow hexagonal prisms to form a hollow core-shell structure. The obtained Vs-ZIS6INO heterostructrue exhibited much enhanced activity of the production of H2 and H2O2 by the light-driven water splitting. In particular, under visible light irradiation (λ > 420 nm), the rate of generation of H2 of Vs-ZIS6INO sample containing 30 wt% Vs-Zn3In2S6 (30Vs-ZIS6INO) could reach 3721 μmol g-1h-1, which was 87 and 6 times higher than those of Zn3In2S6 (43 μmol g-1h-1) and Vs-Zn3In2S6 (586 μmol g-1h-1), respectively. Meanwhile, 30Vs-ZIS6INO could exhibit the rate of H2O2 production of 483 μmol g-1h-1 through the dual pathways of indirect 2e- oxygen reduction (ORR) and water oxidation (WOR) without adding any sacrifice agents, far exceeding In2O3 (7 μmol g-1h-1) and Vs-Zn3In2S6 (58 μmol g-1h-1). The excellent photocatalytic activities of H2 and H2O2 generations of Vs-ZIS6INO sample might result from the synergistic effect of the sulfur vacancy, hollow core-shell structure, and Z-scheme heterostructure, which accelerated the electron delocalization, enhanced the absorption and conversion of solar energy, reduced the carrier diffusion distance, and ensured high REDOX ability. In addition, the possible photocatalytic mechanisms for the production of H2 and H2O2 were discussed in detail. This study provided a new idea and reference for constructing the novel and efficient inorganic semiconductor heterostructures by coordinating vacancy defect and morphology design to adequately utilize water splitting for the production of clean energy.

Highly efficient recovery of Zn (II) from zinc-containing wastewater by tourmaline tailings geopolymers to in-situ construct nanoscale ZnS for the photodegradation of tetracycline hydrochloride

While treating zinc-containing wastewater, recovering zinc for reuse as a secondary resource has significant environmental and economic benefits. Herein, based on the alkali-activated tourmaline tailings geopolymers (TTG) after adsorption of zinc ions (Zn (II)), a series of new composites with in-situ construction ZnS nanoparticles on TTG (ZnS/TTG) were synthesized, and used as photocatalysts for the photodegradation of tetracycline hydrochloride (TCH) in solution. Specifically, ZnS nanoparticles were uniformly and stably distributed in the layered structure of TTG, interweaving with each other to generate an interfacial electric field, which could induce more photocarrier generation. Meanwhile, TTG acted as an electron acceptor to accelerate the electron transfer at the interface, thus enhancing the photodegradation activity for TCH. The active radical quenching experiments combined with the ESR indicated that the active species produced during the photocatalytic degradation of TCH by ZnS/TTG composites were •O2- and photogenerated h+. When the initial concentration of Zn (II) was 60 mg/L, the synthesized 60-ZnS/TTG composites (0.5 g/L) reached 91.53% degradation efficiency of TCH (10 mg/L) at pH = 6. Furthermore, the possible pathways and mechanism of 60-ZnS/TTG composites photodegraded TCH were revealed with the aid of degraded intermediates. This report not only proposed valuable references for reusing heavy metal ions and removing TCH from wastewater, but also provided promising ideas for realizing the conversion of used adsorbents into high-efficiency photocatalysts.

Controllable fabrication of SbxBi2-xS3 solid solution photocatalysts with superior elimination for Cr(VI)

The development of environmentally friendly and cost-effective photocatalysts is of vital significance for the effective removal of heavy metal contamination in water, but it is still a crucial challenge. Herein, the novel SbxBi2-xS3 solid solution photocatalysts with a certain amount of sulfur vacancy were prepared by adjusting the molar ratio of Sb to Bi through a simple hydrothermal strategy, and was applied to the effective photocatalytic reduction of hexavalent chromium (Cr(VI)). Sb1.75Bi0.25S3 with optimized ratio has superior reduction performance of Cr(VI), and the photocatalytic efficiency of Cr(VI) can achieve 91.9 % within 1 h of visible light illumination. The remarkable catalytic efficiency is due to the more applicable band structure of the solid solution photocatalyst, which is conducive for the photocatalytic reaction. Moreover, the substitution of Bi causes the crystal distortion of Sb2S3 and induce the generation of sulfur defects, which can effectively capture photoelectrons, accelerate the carriers separation, and improve the reduction performance. This study provides a hopeful photocatalyst for wastewater purification and promotes the exploration of solid solution photocatalyst in water environment remediation.

Unlocking solar energy's potential: Dual photocatalytic activities of g-C3N4/Sb2S3 for hydrogen evolution and tetracycline degradation in sunlight

This study focuses on developing a g-C3N4/Sb2S3 heterojunction photocatalyst with different g-C3N4 to Sb2S3 weight ratios (1:1, 1:3, and 3:1) for degrading tetracycline (TC) pollutants. The 1:3 ratio (13 GS) exhibited optimal photocatalytic performance, achieving 99% TC degradation under sunlight within 120 min, compared to 78.4% under visible light and 38% under UV light. The 13 GS catalyst demonstrated strong reusability, maintaining 80% degradation efficiency after six cycles. Scavenger experiments identified hydroxyl radicals as crucial for TC degradation, with DMSO reducing activity by 30%. The photocatalyst also showed high hydrogen production with an apparent quantum efficiency (AQE) of 19.8% under standard conditions, and improved AQE in acidic (23%) and basic (22.7%) conditions, and with CH3OH (23.2%). This g-C3N4/Sb2S3 heterojunction offers a promising solution for degrading toxic contaminants and has the potential for solar-powered applications.

Cocreation of photogenerated electron and hole collectors on polymeric carbon nitride synergistically promotes carrier separation and reaction kinetics towards propelling photocatalytic hydrogen evolution

It is a challenging issue for the creation of photogenerated carrier collectors on the photocatalyst to drive charge separation and promote reaction kinetics in the photocatalytic reaction. Herein, based on one-step dual-modulation strategy, IrO2 nanodots are modified at the edge of polymeric carbon nitride (PCN) nanosheets and atomically dispersed Ir atoms are implanted in the skeleton of PCN to obtain a unique Ir-PCN/IrO2 photocatalyst. IrO2 nanodots and atomically dispersed Ir atoms act as hole and electron collectors to synergistically promote the carrier separation and reaction kinetics, respectively, thereby greatly improving the photocatalytic hydrogen evolution (PHE) performance. As a result, without adding additional cocatalyst, the PHE rate over the optimal Ir-PCN/IrO2-2% sample reaches up to 1564.4 μmol h-1 g-1 under the visible light irradiation, with achieving an apparent quantum yield (AQY) of 15.7% at 420 nm.

Precisely Assembling a CoO Cocatalyst onto Tb4O7/CN and Pt-Tb4O7/CN for Promoting Photocatalytic Overall Water Splitting

Photocatalytic overall water splitting (POWS) is a promising approach for solar-to-hydrogen conversion. For achieving this target, it is urgent to develop efficient photocatalysts. Constructing a heterojunction and loading a cocatalyst are two effective strategies for enhancing POWS. However, how to achieve the cooperation of loading the cocatalyst site with the charge separation of a heterojunction remains a huge challenge. Herein, we present an ingenious method: precisely assembling a H2O2-producing cocatalyst CoO on Tb4O7/CN. Assembling CoO on CN of Tb4O7/CN improves the photoinduced electron-hole pair separation and promotes the POWS performance. Inversely, engineering CoO on Tb4O7 leads to production of Co, deactivating POWS performance with a H2-evolution rate 5.2 times lower than that of Tb4O7/CN. Furthermore, we precisely assemble CoO on the CN section of Pt-oriented Pt-Tb4O7/CN. The bioriented CoO and Pt cooperatively promote photogenerated carrier separation. Consequently, the prepared Pt-Tb4O7/CN-CoO exhibits spectacularly high POWS activity. The H2-evolution rate reaches 450 μmol h-1 g-1, which is about 9.4 times higher than that of the initial Tb4O7/CN. The apparent quantum yield (AQY) for H2 evolution at 420 nm reaches 14.1%, surpassing those of most reported CN-based photocatalysts. This work offers an approach to precisely load cocatalysts on heterojunctions. These findings provide insights for designing cocatalyst-decorated heterojunctions for POWS.

Gamma-irradiated stibnite thin films set a remarkable benchmark performance for photoelectrochemical water splitting

The study sets out to show the positive impact of sulfur vacancy engineering on the structural, morphological, optical, electrical, and photoelectrochemical (PEC) properties of Sb2S3 films synthesized using the spin coating technique. The produced films were exposed to γ-irradiation with different doses from 0 to 20 kGy. We have demonstrated the formation of sulfur vacancies and loss of oxygen content in the irradiated samples. XRD measurements revealed that all films exhibit a polycrystalline structure, and the crystallite size increases with the rising radiation dose, reaching the highest value of 87.4 nm measured for the Sb2S3 film irradiated with 15 kGy. The surface roughness of the irradiated samples increases with increasing γ-irradiation dose. The increase in surface roughness not only raises the active sites but enhances the conductivity of the Sb2S3 material as well. The wettability properties of the irradiated films were affected by γ-irradiation doses and the sample irradiated with 15 kGy exhibited the lowest hydrophobicity compared to others. The Hall measurements reveal that irradiated samples exhibit p-type semiconductor behavior. The optical band gap decreased progressively from 1.78 eV to 1.60 eV up to the irradiation dose of 15 kGy and slightly increased thereafter. The irradiated sample with 15 kGy showed a maximum photocurrent density of ca. 1.62 mA cm-2 at 0 V vs. reverse hydrogen electrode (RHE) under AM 1.5 G illumination with applied bias photon-to-current efficiency (ABPE) of 0.82% at 0.47 V vs. RHE, suggesting superior PEC water splitting performance compared to other samples. At 0 V vs. RHE and 648 nm, the incident photon current efficiency (IPCE) and absorbed photon current efficiency (APCE) of the photocathode irradiated with 15 kGy are significantly higher than those of the other photocathodes with values of 9.35% and 14.47%, respectively. Finally, Mott-Schottky measurement was also performed on all photocathodes to estimate their acceptor density and flat band potential.

Multisite Cocatalysis: Single atomic Pt2+/Pt0 active sites synergistically improve the simulated sunlight driven H2O-to-H2 conversion performance of Sb2S3 nanorods

Single atomic metal (SAM) cocatalysis is a potential strategy to improve the performance of photocatalytic materials. However, the cocatalytic mechanism of SAM sites in different valence states is rarely reported. Herein, single atomic Pt2+/Pt0 active sites were anchored on Sb2S3 nanorods to synergistically improve the photoactivity for hydrogen production under simulated sunlight. Experimental results and density functional theory calculations indicated that the coexistence of single atomic Pt2+/Pt0 sites synergistically improves the broadband light harvesting and promotes the Sb2S3-to-Pt electron transfer following inhibited photoexciton recombination kinetics and enhanced H proton adsorption capacity, resulting higher and more durable photoactivity for hydrogen production. Therefore, the optimal Sb2S3-Pt0.9‰ composite catalyst achieved remarkably enhanced hydrogen evolution rate of 1.37 mmol∙g-1∙h-1 (about 105-fold greater of that of Sb2S3 NRs) under faintly alkaline condition, and about 5.41 % of apparent quantum yield (AQY700 nm) was achieved, which shows obvious superiority in hydrogen production by contrasting with the reported Sb2S3-based photocatalysts and conventional semiconductor photocatalytic materials modified with noble metals. This study elucidate a well-defined mechanism of multisite cocatalysis for photoactivity improvement.

2D Z-scheme ZnIn2S4/g-C3N4 heterojunction based on photoelectrochemical immunosensor with enhanced carrier separation for sensitive detection of CEA

Semiconducting materials based on photoelectrochemical (PEC) sensors have been widely utilized for detection. Meanwhile, the sensitivity of the PEC sensor was limited by low-efficiency carrier separation. Thus, a novel sandwich-type PEC bioimmunosensing based on 2D Z-scheme ZnIn2S4/g-C3N4 heterojunction as a photosensitive material and BiVO4 as a photoquencher was designed for the sensitive detection of carcinoembryonic antigen (CEA). Firstly, the 2D ZnIn2S4/g-C3N4 structure provided a multitude of activated sites which facilitated the loading of the capture antibody (Ab1). Secondly, the Z-scheme heterojunction had a high redox capacity while promoting the rapid separation and migration of photogenerated electron-hole pairs (e-/h+). Thus it was able to consume more electron donors to a certain extent, resulting in a higher initial photocurrent. In addition, BiVO4 with large spatial potential resistance was introduced for the first time to realize signal amplification. BiVO4 could not only compete with substrate materials for electron donors, but also effectively prevent electron donors from contacting the substrate, further reducing the photocurrent signal. Under optimized conditions, the sensor had a favorable detection range (0.0001-100 ng/mL) to CEA and a low detection limit of 0.03 pg/mL. With high specificity, excellent stability, and remarkable reproducibility, this sensor provided a new perspective for constructing accurate and convenient PEC immunosensor for bioanalysis and early disease diagnosisdisease diagnosis.

An innovative Z-type Sb2S3/In2S3/TiO2 heterostructure: superior performance in the photocatalytic removal of levofloxacin and mechanistic insight

In this study, Sb2S3/In2S3/TiO2 (SIT) heterojunction photocatalysts were prepared by a simple two-step hydrothermal method and applied to the photocatalytic degradation of levofloxacin (LEV). After 160 min of reaction under visible light, the SIT heterojunction photocatalyst degraded 10 mg L-1 LEV at a rate of 86.7%. The degradation of LEV follows pseudo-first-order kinetics with a rate constant 1.16 × 10-2 min-1, which is 1.42, 1.22 and 1.05 times higher than that of TiO2, SI and IT, respectively. Meanwhile, the SIT photocatalysts also showed high photocatalytic activity for other antibiotics. The enhanced photocatalytic activity of the ternary heterostructures was attributed to the full-spectrum response and the synergistic effect of the dual Z-type heterojunctions, which improved the visible light absorption and facilitated the charge separation. In addition, ˙OH and ˙O2- play a dominant role in the photodegradation process. This work contributes to the design of novel photocatalytic materials with dual Z-type heterojunctions and efficient photocatalysts for the degradation of antibiotics.

Designing Z-scheme In2O3 @ZnIn2S4 core-shell heterojunctions for enhanced photocatalytic multi-pollutant removal

In water bodies, the coexistence of and interaction between multiple pollutants complicate remediation. In this study, the In2O3 @ZnIn2S4 Z-scheme heterojunction with a stratified core-shell structure was constructed and used to remove multiple pollutants (tetracycline hydrochloride and Cr(VI)). The large number of active sites and the mechanism of photogenerated charge separation ensured the substantially enhanced catalytic activity of this photocatalyst, making it superior to In2O3 nanospheres and pure ZnIn2S4. The optimised In2O3 @ZnIn2S4 nano-flowers (In2O3 @ZnIn2S4 NFs) realised 99.8% removal of tetracycline hydrochloride and 100% removal of Cr(VI) within 60 min under visible-light. The material's high stability was demonstrated by five experiment cycles. Effects of organics, inorganics, and pH about the photocatalytic performance of the optimised In2O3 @ZnIn2S4 NFs when tetracycline hydrochloride and Cr(VI) coexist were also explored. Finally, the intermediates and degradation pathways were analysed, and the possible photocatalytic mechanism was also investigated by performing density functional theory calculations.

Epitaxial grown [hk1] oriented 2D/1D Bi2O2S/Sb2S3 heterostructure with significantly enhanced photoelectrochemical performance

Bismuth oxysulfide (Bi2O2S) is a layered material with high carrier mobility, excellent light absorption characteristic and good stability. However, there are few reports about the use of Bi2O2S in photoelectrochemical (PEC) water splitting. In this paper, Bi2O2S nanosheets (NSs) films were prepared on FTO substrates by one-step hydrothermal method, which broke the traditional powder state of Bi2O2S prepared. Based on the high lattice matching between antimony sulfide (Sb2S3) and bismuth sulfide (Bi2S3) obtained from the topological transformation of partial Bi2O2S, Sb2S3 nanorods (NRs) with [hk1] predominant orientation were epitaxially grown on the surface of Bi2O2S to establish a transport channel for rapid carrier migration. Titanium dioxide (TiO2) electron transport layer with oxygen vacancies was introduced into the back to capture and release electrons, further reducing the recombination rate. The photocurrent density of TiO2/Bi2O2S/Sb2S3-annealed photoelectrode at 1.23 V vs. RHE was 4.37 mA/cm2, which was 13.7 times that of monomer Bi2O2S. In addition, the TiO2/Bi2O2S/Sb2S3-annealed photoelectrode had lower charge transfer resistance and the IPCE value up to 48.22%. This study is of great significance for the application of Bi2O2S based photoelectrodes in the field of PEC water splitting.

Constructed a novel of Znln2S4/S-C3N4 heterogeneous catalyst for efficient photodegradation of tetracycline

Despite S-doped C3N4 can exhibit more efficient photo-reactivity than pure C3N4, there is still some space to further improve the detaching efficiency of electron-hole and enhance the photocatalytic efficiency of S-C3N4. The construction of heterojunction is an effective method to promote the photocatalytic efficiency. ZnIn2S4, as a novel photocatalyst, its VB (1.37 V) and CB (- 1.09 V) can match with S-C3N4. Therefore, we hope to construct the ZnIn2S4/S-C3N4 heterojunction for boosting the photocatalytic activity of S-C3N4. In this paper, ZnIn2S4/S-C3N4 heterojunction was prepared through hydrothermal method using S-C3N4, ZnCl2, InCl3·4H2O, and thioacetamide as raw materials and heated at 160 °C for 16 h. The optimum 18% ZnIn2S4/S-C3N4 nanocomposites exhibit dramatically enhanced photocatalytic performance for degradation of tetracycline with 86.3% removal rate within 120 min, higher than 50% degradation efficiency of pure S-C3N4. And in the process of photodegradation for tetracycline, the largest contribution rate is the photo-excited cavity (h+), followed by ·O2- and ·OH. Herein, we have provided a good example for removing antibiotic residues by using S-C3N4-based heterojunction towards environmental remediation.

Carbon Dots as an Electron Acceptor in the ZnIn2S4@MIL-88A Heterojunction for Enhanced Visible-Light-Driven Photocatalytic Hydrogen Evolution

In this study, visible-light-responsive carbon dots (CDs)/ZnIn2S4@MIL-88A (C/ZI@ML) photocatalysts were successfully prepared through in situ loading CDs and ZnIn2S4 nanosheets on MIL-88A(Fe) to form a ternary heterojunction. The detailed characterization indicated that the two-dimensional ZnIn2S4 nanosheets were uniformly coated on the surface of MIL-88A(Fe), and ZnIn2S4/MIL-88A(Fe) exhibited enhanced photocatalytic hydrogen production performance (1259.63 μmol h-1 g-1) compared to that of pristine MIL-88A(Fe) and ZnIn2S4 under visible light illumination. After introduction of CDs into ZnIn2S4/MIL-88A(Fe), the C/ZI@ML catalyst remarkably enhanced the photocatalytic activity and the hydrogen evolution rate of 1C/ZI@ML was up to 3609.23 μmol g-1 h-1. The photoinduced charge carriers of C/ZI@ML can be efficiently separated and migrated because of the close contacted interface, synergistic effect, and suitable band structure. In combination with photoelectrochemical experiments and electron paramagnetic resonance spectra, a possible photocatalytic mechanism over C/ZI@ML was proposed. This work demonstrated a facile preparation method for fabricating efficient visible-light-driven heterojunction photocatalysts.

Facile Construction of 2D/2D ZnIn2S4-Based Bifunctional Photocatalysts for H2 Production and Simultaneous Degradation of Rhodamine B and Tetracycline

A two-dimensional/two-dimensional (2D/2D) TiO2/ZnIn2S4 photocatalyst was reasonably proposed and constructed by a two-step oil bath-hydrothermal method. TiO2 nanosheets uniformly grown on the surface of ZnIn2S4 nanosheets and a synergetic effect between the TiO2 and ZnIn2S4 could highly contribute to improving the specific surface area and hydrophilicity of ZnIn2S4 as well as accelerating the separation and transfer of photon-generated e--h+ pairs, and thus enhancing the visible-light photocatalytic degradation and H2 evolution performance of ZnIn2S4. Rhodamine B (RhB) and tetracycline (TC) were simultaneously selected as the target pollutants for degradation in the work. The optimum photocatalytic RhB and TC degradation properties of TiO2/ZnIn2S4-10 wt% were almost 3.11- and 8.61-fold higher than that of pure ZnIn2S4, separately, while the highest photocatalytic hydrogen evolution rate was also observed in the presence of TiO2/ZnIn2S4-10wt% and 4.28-fold higher than that of ZnIn2S4. Moreover, the possible photocatalytic mechanisms for enhanced visible-light photocatalytic degradation and H2 evolution were investigated and proposed in detail. Our research results open an easy pathway for developing efficient bifunctional photocatalysts.

A review on potential sulfide-based ternary chalcogenides for emerging photo-assisted water purification applications

Sulfide-based ternary chalcogenides have been recognized widely as exceptional photocatalysts, thanks to their narrow band gap enabling them to harvest solar energy to the maximum extent. They provide excellent optical, electrical, and catalytic performance and are of abundant use as a heterogeneous catalyst. Among sulfide-based ternary chalcogenides, compounds exhibiting AB2X4 structure form a new class of materials with excellent stability in photocatalytic performance. In the AB2X4 family of compounds, ZnIn2S4 is one of the top performing photocatalyst for energy and environmental applications. However, to date, only limited information is available on the mechanism behind the photo-induced migration of charge carriers in ternary sulfide chalcogenides. Ternary sulfide chalcogenides with their visible region activity and substantial chemical stability greatly depend on crystal structure, morphology, and optical characteristics for their photocatalytic activity. Hence, in this review, a comprehensive assessment of the reported strategies for enhancement of the photocatalytic efficiency of this compound is presented. In addition, a meticulous investigation of the applicability of ternary sulfide chalcogenide compound ZnIn2S4, in particular, has been delivered. Also, the photocatalytic behavior of other sulfide-based ternary chalcogenides for water remediation applications has also been briefed. Finally, we conclude with an insight into the challenges and future advancements in the exploration of ZnIn2S4-based chalcogenide as a photocatalyst for various photo-responsive applications. It is believed that this review could contribute to a better understanding of ternary chalcogenide semiconductor photocatalysts for solar-driven water treatment applications.

Hard-Soft Core-Shell Architecture Formation from Cubic Cobalt Ferrite Nanoparticles

Cubic bi-magnetic hard-soft core-shell nanoarchitectures were prepared starting from cobalt ferrite nanoparticles, prevalently with cubic shape, as seeds to grow a manganese ferrite shell. The combined use of direct (nanoscale chemical mapping via STEM-EDX) and indirect (DC magnetometry) tools was adopted to verify the formation of the heterostructures at the nanoscale and bulk level, respectively. The results showed the obtainment of core-shell NPs (CoFe₂O₄@MnFe₂O₄) with a thin shell (heterogenous nucleation). In addition, manganese ferrite was found to homogeneously nucleate to form a secondary nanoparticle population (homogenous nucleation). This study shed light on the competitive formation mechanism of homogenous and heterogenous nucleation, suggesting the existence of a critical size, beyond which, phase separation occurs and seeds are no longer available in the reaction medium for heterogenous nucleation. These findings may allow one to tailor the synthesis process in order to achieve better control of the materials' features affecting the magnetic behaviour, and consequently, the performances as heat mediators or components for data storage devices.

Oxygen Vacancies-Rich S-Cheme BiOBr/CdS Heterojunction with Synergetic Effect for Highly Efficient Light Emitting Diode-Driven Pollutants Degradation

Recently, the use of semiconductor-based photocatalytic technology as an effective way to mitigate the environmental crisis attracted considerable interest. Here, the S-scheme BiOBr/CdS heterojunction with abundant oxygen vacancies (Vo-BiOBr/CdS) was prepared by the solvothermal method using ethylene glycol as a solvent. The photocatalytic activity of the heterojunction was investigated by degrading rhodamine B (RhB) and methylene blue (MB) under 5 W light-emitting diode (LED) light. Notably, the degradation rate of RhB and MB reached 97% and 93% in 60 min, respectively, which were better than that of BiOBr, CdS, and BiOBr/CdS. It was due to the construction of the heterojunction and the introduction of Vo, which facilitated the spatial separation of carriers and enhanced the visible-light harvest. The radical trapping experiment suggested that superoxide radicals (·O₂^-) acted as the main active species. Based on valence balance spectra, Mott-Schottky(M-S) spectra, and DFT theoretical calculations, the photocatalytic mechanism of the S-scheme heterojunction was proposed. This research provides a novel strategy for designing efficient photocatalysts by constructing S-scheme heterojunctions and introducing oxygen vacancies for solving environmental pollution.

Surface Coordination of Pd/ZnIn2S4 toward Enhanced Photocatalytic Activity for Pyridine Denitrification

New surface coordination photocatalytic systems that are inspired by natural photosynthesis have significant potential to boost fuel denitrification. Despite this, the direct synthesis of efficient surface coordination photocatalysts remains a major challenge. Herein, it is verified that a coordination photocatalyst can be constructed by coupling Pd and CTAB-modified ZnIn₂S₄ semiconductors. The optimized Pd/ZnIn₂S₄ showed a superior degradation rate of 81% for fuel denitrification within 240 min, which was 2.25 times higher than that of ZnIn₂S₄. From the in situ FTIR and XPS spectra of 1% Pd/ZnIn₂S₄ before and after pyridine adsorption, we find that pyridine can be selectively adsorbed and form Zn⋅⋅⋅C-N or In⋅⋅⋅C-N on the surface of Pd/ZnIn₂S₄. Meanwhile, the superior electrical conductivity of Pd can be combined with ZnIn₂S₄ to promote photocatalytic denitrification. This work also explains the surface/interface coordination effect of metal/nanosheets at the molecular level, playing an important role in photocatalytic fuel denitrification.