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Chitosan-stabilized iron-copper nanomaterials (CS-nZVI/Cu) were successfully prepared and applied to the nitrate removal. Batch experiments were conducted to examine the effects of experimental parameters on nitrate removal, including Cu loading, CS-nZVI/Cu dosages, initial nitrate concentrations, and initial pHs. From the experimental date, it was concluded that CS-nZVI/Cu has a high nitrate removal efficiency, which can be more than 97%, respectively, at Cu loading = 5%, dosages of CS-nZVI/Cu = 3 g/L, initial nitrate concentrations of 30~120 mg/L, and initial pH values = 2~9. Additionally, the kinetic data for CS-nZVI/Cu were found to fit well with the first-order kinetic model with a rate constant of 0.15 (mg∙L) 1-n /min, where n=1. The Langmuir model showed a good fit for NO 3 - removal, indicating that monolayer chemisorption occurred. The SEM and TEM analyses showed that the addition of chitosan resulted in improved dispersion of the CS-nZVI/Cu. The CS-nZVI/Cu nanomaterials have a more complete elliptical shape and are between 50 and 100 nm in size. The XRD analysis showed that the chitosan encapsulation reduced the oxidation of the iron component and the main product was Fe 3 O 4 . The FT-IR analysis showed that the immobilization of chitosan and the iron was accomplished by the ligand interaction. The nitrogen adsorption-desorption isotherm results showed that the CS-nZVI/Cu specific surface area and pore volume decreased significantly after the reaction. Adsorption, oxidation, and reduction are possible mechanisms for nitrate removal by CS-nZVI/Cu. The XPS analysis investigated the contribution of nZVI and Cu in the removal mechanism. Adding copper accelerates the reaction time and rate. In addition, nZVI played a vital role in reducing nitrate to N 2 . Based on these results, it looks like CS-nZVI/Cu could be a satisfactory material for nitrate removal., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Combining metal-organic frameworks with electrospinning technology, this work employs coaxial electrospun fibers decorated with ZIF-67 as precursors. The Fe3+/Co2+/Ni2+ ions in the electrospun fibers are converted into FeCoNi alloy nanoparticles which catalyze the pyrolysis of ZIF-67 on the fiber surface to generate reticulated carbon microfibers. This produces an efficacious bifunctional oxygen electrocatalyst. This new N-doped carbon hierarchical network (NCHNs) catalyst with a distinct secondary reticulated carbon structure possesses larger surface area and pore volume. Besides, the decoration of FeCoNi nanoparticles on the NCHNs provides effective active sites. With rapid mass and electron transfer between the hollow fibers, the synergistic effect between the FeCoNi nanoparticles and the layered carbon network can contribute to the high activity and kinetics of oxygen electrochemistry. At 10 mA cm−2, the FeCoNi/NCHNs exhibit an ORR half-wave potential of 0.885 V and an OER potential of 1.610 V, which exceeds that of the existing Pt/C and RuO 2 catalysts. Furthermore, the FeCoNi/NCHNs-based rechargeable Zn-Air battery has an excellent power density (160.5 mV cm−2), high open-circuit voltage (1.48 V), large specific capacity (792 mAh g−1) and excellent cycling stability (>200 h). This work provides a convenient method for designing high performance and low cost catalysts. [Display omitted] • Pyrolysis of electrospun fibers yields FeCoNi embedded in N-doped carbon fiber. • FeCoNi catalyzes the generation of carbon nanotubes in the pyrolysis of ZIF-67. • Carbon nanotubes/microfibers create N-doped carbon hierarchical networks (NCHNs). • FeCoNi/NCHNs shows excellent bifunctional oxygen catalytic activity and durability. • Zinc-air batteries based on FeCoNi/NCHNs exhibit high power density and capacity. [ABSTRACT FROM AUTHOR]

Abstract: Zinc-decorated silica-coated magnetic nanoparticles (ZnSiMNPs) were prepared by adsorbing zinc onto colloidal silica. These nanoparticles were used for the rapid purification of 6×His-tagged recombinant phycobiliprotein. The surface changes in the magnetic nanoparticles after zinc adsorption were characterized by transmission electron microscopy. The adsorption of the 6×His-tagged phycobiliprotein onto ZnSiMNPs in 10mM PBS at 25°C was found to follow the Langmuir isotherm. ZnSiMNPs could be used to extract 6×His-tagged phycobiliprotein from lysate to single-band purity, as determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. No spectral variation was observed in the purified phycobiliprotein. Thus, ZnSiMNPs served as a useful tool for the magnetic separation and delivery of the 6×His-tagged phycobiliprotein. [Copyright &y& Elsevier]

Due to slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during discharging and charging processes, it is essential to rationally design and synthesize non-precious metal bifunctional electrocatalysts with good performance for metal-air batteries. Herein, Ag-MnFe2O4 heterojunction nanoparticles supported on N, S, P-codoped graphene (NSPG) are developed with enhanced ORR and OER bifunctional electrocatalytic activities and stability. In contrast, S, P-doped graphene (SPG) and N, P-doped graphene (NPG) show less stabilization for the heterojunction particles. For example, under alkaline conditions, the ORR half-wave potential of Ag-MnFe2O4/NSPG can reach 0.831 V, and the over potential for OER is 0.56 V at the current density 10 mA·cm−2. Furthermore, Ag-MnFe2O4/NSPG shows better methanol resistance and durability than Pt/C catalysts. [ABSTRACT FROM AUTHOR]

Iron/nitrogen co-doped carbon materials (Fe/N-C) have been extensively investigated as oxygen reduction reaction (ORR) catalysts in alkaline medium. Here, Fe 3 O 4 nanoparticles decorated carbon black is encapsulated with polypyrrole and subsequently utilized as a precursor to synthesize a highly efficient ORR catalyst through pyrolysis. Interestingly, this catalyst consists of yolk-shell Fe@FeN x and N-doped porous carbon, demonstrating a synergistically improved ORR activity. It shows better durability, Pt-comparable activity, and superior tolerance against methanol crossover under alkaline conditions. Control experiments confirm that yolk-shell Fe@FeN x nanoparticles provide efficient catalytic sites and facilitate charge transfer in ORRs. Thus, this study provides a new kind of Fe/N-C electrocatalyst synthesized to be nitride rather than carbide simply with a heat-treatment under N 2 atmosphere. Image 1 • Fe@FeN x /N-C consist of yolk-shell Fe@FeN x nanoparticles and N-doped mesoporous carbon. • Fe@FeN x /N-C are synthesized with pyrolysis of polypyrrole-encapsulated Fe 3 O 4 /C. • Yolk-shell Fe@FeN x provides catalytic sites and facilitates charge transfer in ORR. • Fe@FeN x /N-C show excellent ORR activity and durability in alkaline media. [ABSTRACT FROM AUTHOR]

Heterogeneous nanoparticles with synergistic effects between different composites are potential catalysts with bifunctional catalytic activity for oxygen reduction (ORR) and oxygen evolution reaction (OER). Herein, heteroatoms such as N and S are doped into graphene substrates to improve catalytic activity and structural stability of Ag-MnFe 2 O 4 nanoparticles. Interestingly, these particles keep a primarily heterogeneous structure for their assembly on N, S-codoped graphene (NSG), while Ag domains shrink on S-doped graphene (SG) or N-doped graphene (NG). Subsequently, Ag-MnFe 2 O 4 /NSG shows the best bifunctional catalytic activity due to the improved stability of Ag-MnFe 2 O 4 NPs on NSG and enhanced bonding energy between supports and particles. The Koutecky-Levich plots confirm a major four-electron reaction pathway for the ORRs on Ag-MnFe 2 O 4 /NSG. Meanwhile, Ag-MnFe 2 O 4 /NSG exhibits higher stability and better methanol tolerance than commercial Pt/C. Therefore, Ag-MnFe 2 O 4 /NSG with bi-functional catalytic activity for ORR and OER is a promising non-Pt catalyst candidate. Unlabelled Image • Heteroatoms such as N and S are doped into graphene to make NSG supports. • Heterogeneous structures of Ag-MnFe 2 O 4 nanoparticles maintain on NSG supports. • NSG supports improve the catalytic activity of the Ag-MnFe 2 O 4 /NSG. • Ag-MnFe 2 O 4 /NSG shows promising bi-functional catalytic activity for ORR and OER. [ABSTRACT FROM AUTHOR]

• Heterogeneous FeNi 3 /NiFe 2 O 4 nanoparticles are embedded in modified graphene matrix. • Synergistic effects of FeNi 3 /NiFe 2 O 4 and graphene to enhance electrocatalytic activities. • The DSSC with FeNi 3 /NiFe 2 O 4 @mGr achieves a power conversion efficiency of 12.14%. • The FeNi 3 /NiFe 2 O 4 @mGr device remains 90% efficiency up to 42 days under ambient conditions. The development of low cost electrocatalysts with excellent I−/I 3 − redox reaction efficiency is critically important for practical applications of dye-sensitized solar cells (DSSCs). Nevertheless, it is difficult to simultaneously improve the activity and stability of catalysts. Herein, heterogeneous FeNi 3 /NiFe 2 O 4 nanoparticles are successfully embedded in modified graphene (mGr) matrix with network structure. As-prepared FeNi 3 /NiFe 2 O 4 @mGr shows excellent electrocatalytic activities and high stability. The DSSCs with FeNi 3 /NiFe 2 O 4 @mGr as counter electrodes demonstrate a high power conversion efficiency of 12.14%, which is superior to that of platinum (Pt, 8.31%). Also, the FeNi 3 /NiFe 2 O 4 @mGr device remains 90% efficiency up to 42 days under ambient conditions without encapsulation. Therefore, the FeNi 3 /NiFe 2 O 4 @mGr composite can be further developed as an environmentally friendly, inexpensive, and efficient counter electrode material for DSSCs. [ABSTRACT FROM AUTHOR]

• Heterostructured CoFe 2 O 4 -TiO 2 nanoparticles show an excellent photocatalytic property. • CoFe 2 O 4 -TiO 2 is also proved to be an efficient catalyst for O 2 reduction reaction (ORR). • The rapid growth of O 2 –∙ by CoFe 2 O 4 -TiO 2 results in photocatalytic activity improvement. • Synergistic operation of photocatalysis and catalytic ORR is conducted by CoFe 2 O 4 -TiO 2. The improved photocatalytic activity of TiO 2 with the addition of spinel CoFe 2 O 4 as an effective catalyst for O 2 reduction reaction (ORR) is studied and proved in this study. CoFe 2 O 4 -TiO 2 heterostructure nanoparticles are prepared by a reflux condensation and two-step hydrolysis-hydrothermal method. The addition of trace CoFe 2 O 4 onto TiO 2 can improve its affinity to O 2 , generate a faster transportation of photo-induced carriers, but hardly affect band structure. With an appropriate amount of CoFe 2 O 4 to TiO 2 , a remarkable acceleration occurs in photocatalytic decolorization of dye wastewater, and the calculated apparent kinetic constant (k app) of the composite (0.020 min−1) is 2.4 and 5.6 times of pure TiO 2 (0.0085 min−1) and CoFe 2 O 4 (0.0036 min−1), respectively. Quenching experiments with different radical scavengers show that O 2 –∙ is the key oxidative radical in all photocatalytical reactions. Meanwhile, the rapid growth of O 2 –∙ production by CoFe 2 O 4 -TiO 2 is proved to be a major cause for photocatalytic performance improvement. Furthermore, an improved electrochemical ORR catalytic ability by CoFe 2 O 4 -TiO 2 is verified and the 2-plus-2 electron route generates the same product (H 2 O 2) as the photocatalytic process. Therefore, the synergistic operation of photocatalytic and catalytic ORR process by CoFe 2 O 4 -TiO 2 resulted in a rapid degradation of dye wastewater. [ABSTRACT FROM AUTHOR]