Mn Sites Research Articles

Nature-inspired N, O Co-Coordinated Manganese Single-Atom Catalyst for Efficient Hydrogen Peroxide Electrosynthesis.

The two-electron oxygen reduction reaction (2e- ORR) is a pivotal pathway for the distributed production of hydrogen peroxide (H2O2). In nature, enzymes containing manganese (Mn) centers can convert reactive oxygen species into H2O2. However, Mn-based heterogeneous catalysts for 2e- ORR are scarcely reported. Herein, we developed a nature-inspired single-atom electrocatalyst comprising N, O co-coordinated Mn sites, utilizing carbon dots as the modulation platform (Mn CD/C). As-synthesized Mn CD/C exhibited exceptional 2e- ORR activity with an onset potential of 0.786 V and a maximum H2O2 selectivity of 95.8%. Impressively, Mn CD/C continuously produced 0.1 M H2O2 solution at 200 mA/cm2 for 50 h in the flow cell, with negligible loss in activity and H2O2 faradaic efficiency, demonstrating practical application potential. The enhanced activity was attributed to the incorporation of Mn atomic sites into the carbon dots. Theoretical calculations revealed that the N, O co-coordinated structure, combined with abundant oxygen-containing functional groups on the carbon dots, optimized the binding strength of intermediate *OOH at the Mn sites to the apex of the catalytic activity volcano. This work illustrates that carbon dots can serve as a versatile platform for modulating the microenvironment of single-atom catalysts and for the rational design of nature-inspired catalysts.

Investigating the multifunctionality of Cu2+ doped LaSrMnO3: understanding structural, optical, and magnetic responses

Abstract This study examines the impact of copper ions (Cu2+) on the structural, optical, and magnetic, characteristics of La0.6Sr0.4Mn1-xCuxO3 (LSMCO) manganites. Various techniques, including X-ray diffraction, field emission scanning electron microscopy, Raman spectroscopy, DC magnetization, and photoluminescence measurements were employed for a comprehensive analysis. Structural examinations revealed that all compositions exhibit a single-phase orthorhombic structure. Raman spectroscopy reveals the structural distortion due to the inclusion of Cu at Mn site. The photoluminescence properties of the manganite were found to be influenced by the excitation wavelength, demonstrating energy transfer from Mn ions. Magnetic investigations indicated that the introduction of Cu leads to a reduction in the saturation magnetization of the manganite.

Trimetallic ZIFs-derived nanoarchitecture for portable wireless electrochemical determination of chlorogenic acid in natural medicine and food samples

In this paper, a novel trimetallic zeolitic imidazolate frameworks (ZnCoMn-ZIFs) was successfully synthesized by a facile one-pot method at room temperature, which was further used to prepare a triatomic site anchored in N-doped carbon (Co2MnN8@C) hybrid nanostructure via a pyrolysis method. The synthesized Co2MnN8@C was modified on the screen-printed carbon electrode, and the modified electrode was used for the portable wireless sensitive determination of chlorogenic acid (CGA) by differential pulse voltammetry. The Co2MnN8@C exhibited large surface area and excellent catalytic activity with increasing Co and Mn sites, which could selectively combine with CGA to enhance the sensitivity of the electrochemical sensor. Under the optimized conditions, the constructed sensor had wider linear ranges for CGA analysis from 0.05–10.0 μmol/L and 10.0–100.0 μmol/L with a detection limit of 0.0075 μmol/L (3S0/S). The sensor was successfully applied to detect CGA in natural medicine and food samples with satisfied recoveries. Therefore, the proposed strategy may stimulate the exploration of trimetallic ZIFs with more active sites for the development of sensitive electrochemical sensors.

Synthesis and structural study of the partially disordered complex hexagonal phase δ1-MnZn9.7.

A detailed structural analysis of the Zn-rich δ1-MnZn9.7 phase using single-crystal X-ray diffraction is presented. The δ1 phase has been synthesized by the high-temperature synthetic route. The structure crystallizes in space group P63/mmc (Pearson symbol hP556) with unit-cell parameters: a = b = 12.9051 (2) Å and c = 57.640 (1) Å. The 556 atoms are distributed over 52 Wyckoff positions in the hexagonal unit cell: seven ordered Mn sites, 37 ordered Zn sites and eight positionally disordered Zn sites. The structure predominantly consists of Frank-Kasper polyhedra (endohedral icosahedra Zn12 and icosioctahedron Zn16) and four distinct types of glue Zn atoms. The structure comprises a 127-atom supercluster (Mn13Zn114), a 38-atom extended Pearce cluster (Mn3Zn35), a 46-atom L-tetrahedron (Mn4Zn42), a Friauf polyhedron (Zn17), a disordered icosahedral cluster (MnZn12) and four glue Zn atoms. Positionally disordered Zn sites around an Mn site can be visualized as the superimposition of three differently oriented Zn12 icosahedra.

Balancing the redox activity against structure stability in high-voltage manganese/iron-based layered oxide cathodes through copper doping for potassium-ion batteries

Earth-abundant manganese/iron-based layered oxide cathodes display high energy densities in cost-effective potassium-ion batteries, but still encounter severe structure distortions and irreversible phase transformations upon cycling. To ameliorate its structural stability, the highly electronegative but electrochemically inactive Cu2+ is rationally introduced into Mn sites of P3-type K0.5Mn0.8Fe0.2O2 cathode materials to regulate crystal structures and elemental valences toward a balance between redox activity and structure stability. Ranging from 4.2 to 1.5 V, the optimal K0.5Mn0.7Fe0.2Cu0.1O2 cathode material with a lower formation energy and a narrower band gap could present a large initial discharging capacity of 91 mAh g−1 at 50 mA g−1 with an excellent capacity retention of 71.6 % over 50 cycles and a competitive capacity retention of 62.3 % at 100 mA g−1 after 100 cycles. Regardless of its compromised K+ diffusion capabilities from a slightly contracted interlayer, a superior rate performance of 71 mAh g−1 can be achieved at 500 mA g−1, implying a dominant function of structural stability in electrochemical depotassiation/potassiation. Additionally, the dynamic redox activities and high electrochemical reversibility of Mn4+/3+ and Fe4+/3+ couples are verified by ex-situ X-ray photoemission spectroscopies. This solid work would enlighten the novel structural manipulations of layered oxide cathodes for high-voltage potassium-ion batteries.

Exploring the structural, morphology, optical and magnetic properties of ZnCoxMn(2-x)O4 prepared using hydrothermal method

Here we report the structural and physical property of ZnCoxMn(2-x)O4 (x = 0, 0.1 and 0.2) materials. The hierarchical ZnCoxMn2-xO4 (x = 0, 0.1 and 0.2) have been successfully synthesized by hydrothermal method. The surface of the ZnCoxMn(2-x)O4 varies according to its composition which is investigated. The absorption and band gap of the material were measured by UV-Vis diffuse reflectance spectroscopy (DRS) in the range of 200 – 800 nm. It was observed that the band gap gets decreased from the parent compound. The room temperature photoluminescence emission spectra of ZnCoxMn(2-x)O4 (x = 0,0.1 and 0.2) has been investigated. The magnetic property of material shows an antiferromagnetic nature. Further, X-ray photoelectron spectroscopy analysis confirms the substitution of Co on Mn site.

Synthesis and Electrochemical Performance Enhancement of Li2MnSiO4 Cathode Material for Lithium‐Ion Batteries via Mn‐Site Ni Doping

AbstractIn exploring the potential of Li2MnSiO4 as a cathode material for lithium‐ion batteries (LIBs), the key challenges often involve enhancing electronic conductivity and lithium‐ion diffusion rates. To address these issues, this paper proposes the combination of solid‐state doping and a two‐step calcination process to successfully prepare the Li2Mn1−xNixSiO4 series of cathode materials, where Ni substitutes Mn at different doping amounts (x = 0, 0.02, 0.04, 0.06, 0.08). The use of chemically equivalent Ni2+ ions to replace Mn2+ ions is an effective method. Since the ionic radius of Ni2+ is smaller than that of Mn2+, this substitution can create more voids in the lattice structure. These increased voids provide smoother channels for the transport of electrons and lithium ions, thereby improving the material's electrical conductivity. At a Ni doping amount of 0.06, the material exhibits optimal electrochemical performance, achieving a discharge capacity of 155 mAh g−1 at 0.1 C, significantly superior to undoped lithium manganese silicate. The doping of Mn sites with Ni significantly improves the conductivity and lithium‐ion diffusion capabilities of Li2MnSiO4, revealing the tremendous potential of doping strategies in optimizing the performance of LIBs cathode materials.

Mechanism Behind the Enhanced Ferromagnetic Contributions Upon Ru Substitution in Ca3Mn2O7 from X-Ray Absorption Spectroscopies.

We have studied the local structure and electronic and magnetic properties of hybrid improper ferroelectric Ca3Mn2O7 upon Ru substitution at the Mn site by a combination of atomic-selective X-ray absorption spectroscopies in the soft and hard X-ray energy regimes. Ru substitution enhances the macroscopic ferromagnetic contributions, whose origin is here elucidated. In particular, soft X-ray magnetic circular dichroism (XMCD) data indicate that the spin moments of Mn and Ru are aligned in opposite directions, with the effective magnetic moments of Ru being about 1 order of magnitude smaller than for Mn. The XMCD results also demonstrate the presence of an intrinsic ferromagnetic component in the Mn sublattice for Ru contents x ≥ 0.3, although the values of the net Mn magnetic moment are much smaller than expected for a fully saturated Mn4+ magnetic sublattice. Soft and hard X-ray absorption spectroscopy measurements show that Mn keeps a +4 valence state independently of the Ru content, whereas Ru is in an intermediate valence state, ranging between +4.7 (x ≤ 0.1) and +4.4 (x ≥ 0.7). Analysis of the extended X-ray absorption fine structure (EXAFS) signals at the Mn and Ru K-edges suggests the lack of a complete solid solution in the local structure across the entire range of compositions. These findings disclose the existence of charge transfer between Mn and Ru atoms, so the weak ferromagnetic component is attributed to a canting of the antiferromagnetically ordered Mn4+ spins caused by the oxygen-mediated hybridization between localized Mn4+ 3d and itinerant intermediate valence Ru 4d bands, in analogy to the mechanism proposed for ferromagnetism in ordered doubled perovskites with 3d and 4d/5d transition-metal ions. In the present case, disorder prevents the formation of long-range ferromagnetism.

Mn‐Fe dual‐metal Assemblages on Carbon‐coated Al2O3 Spheres for Catalytic Ozonation Oxidation: Structure, Performance, and Reaction Mechanism

Catalysts with high catalytic activity and low production cost are important for industrial application of heterogeneous catalytic ozonation (HCO). In this study, we designed a carbon‐coated aluminum oxide carrier (C‐Al2O3) and reinforced it with Mn‐Fe bimetal assemblages to prepare a high‐performance catalyst Mn‐Fe/C‐Al2O3. The results showed that the carbon embedding significantly improved the abundance of surface oxygen functional groups, conductivity, and adsorption capacity of γ‐Al2O3, while preserving its exceptional mechanical strength as a carrier. The prepared Mn‐Fe/C‐Al2O3 catalyst exhibited satisfactory catalytic ozonation activity and stability in the degradation of p‐nitrophenol (PNP). Electron paramagnetic resonance (EPR) and quenching experiments reveal that radical (•OH and •O2–) and nonradical oxidation (1O2) dominated the PNP degradation process. Theoretical calculations corroborated that the anchored atomic Fe and Mn sites regulated the local electronic structure of the catalyst. This modulation effectively promoted the activation of O3 molecules, resulting in the generation of atomic oxygen species (AOS) and reactive oxygen species (ROS). The economic analysis on Mn‐Fe/C‐Al2O3 revealed that it was a cost‐competitive catalyst for HCO. This study not only deepens the understanding on the reaction mechanism of HCO with transition metal/carbon composite catalysts, also provides a high‐performance and cost‐competitive ozone catalyst for prospective application.

Synergistic effect of Ru single atoms and MnO2 to boost oxygen reduction/evolution activity via strong electronic interaction

Ru-based single-atomic catalysts have shown great potential application in sustainable electrochemical energy conversion/storage devices. Herein Ru single atoms anchored on the surface of MnO2 nanorods (Ru SAs@MnO2) have been successfully constructed by a facile low-temperature solid-phase reaction, which has been confirmed by X-ray adsorption spectra. The synthesized Ru SAs@MnO2 catalyst exhibits a comparable ORR performance with half-wave potential of 0.83 V and a limiting current density of 7.1 mA cm−2 to commercial Pt/C, and high OER performance with the overpotential of 320 mV at 10 mA cm−2. Theoretical calculation results indicate that Mn sites and Ru sites of Ru SAs@MnO2 act as the catalytic ORR and OER sites, respectively, and the synergistic effect between Ru SAs and MnO2 contributes to the improved catalytic performance via strong electronic interaction. When assembled zinc-air batteries, a maximum power density 230.0 mW cm−2 could be delivered at 318.5 mA cm−2.

CO-Free Fuel Processing of Water Gas Shift Feedstocks: Effect of Support on CuMn Spinel Performance

AbstractCleaning up carbon monoxide (CO) in water gas shift feedstocks is crucial for fuel cell applications. The catalytic transformation of CO in hydrogen-rich feeds poses a significant challenge in environmental catalysis. To address this issue, a range of Cu–Mn-based monometallic and bimetallic catalysts with diverse supports (such as alumina, silica, zirconia, and titania) were employed. Temperature programming techniques were utilised to observe the reduction and oxidation behaviours of these catalysts. The investigation involved testing CO oxidation at various temperatures over copper and manganese-based supported catalysts in the presence of H2O and CO2 (simulating realistic conditions). A positive impact of H2O on catalytic performance was noted, whereas CO2 had a suppressive effect. Furthermore, the specific support materials (Al2O3, SiO2, TiO2, and ZrO2) were studied to understand their roles in CO oxidation under realistic conditions. In the presence of water, alumina catalysts containing bimetallic metals (Cu–Mn) exhibited 100% CO conversion even at a lower temperature of 160 °C. Conversely, under the predominant influence of CO2, alumina catalyst (Cu–Mn) showed 55% CO conversion. The exceptional performance was attributed to CO preferential adsorption on highly active Cu–Mn sites and a small H2-oxidative atmosphere of the catalysts. The activity results highlighted the strong dependence of CO conversion on reaction temperatures, the presence of metals, and the types of supports. Overall, these findings suggest the potential use of these catalysts for H2 purification under realistic conditions. Graphical Abstract

Dual‐Carbon Assisted Oxygen Vacancy Engineering for Optimizing Mn(III) Sites to Enhance Zn–air Battery Performances

AbstractOwing to kinetic‐sluggish nature of electrocatalytic oxygen transformation processes, it is pivotal to develop durable and efficient bifunctional air electrode catalysts for fabricating high‐performance Zn–air batteries (ZABs). In this work, oxygen vacancy (Ov) induced Mn(III) sites optimization is achieved via nano‐micro structure modulation. Protonated carbon nitride (p‐C3N4) is applied as a structure‐stiffening module to immobilize α‐MnO2 on N/P‐doped active carbon (NPAC) and induce Ov construction. X‐ray adsorption spectra (XAS) disclose the formation of Ov and Mn(III) sites in MCC, the unit coordination structure is well maintained with the aid of a dual‐carbon strategy. Mn(III) sites efficiently catalyze oxygen reduction/evolution reaction (ORR/OER), MCC shows high half‐wave potential (E1/2) of 0.88 V for ORR and low potential at 10 mA cm−2 (Ej = 10) of 1.64 V for OER. According to density functional theory (DFT) simulations analysis, the gorgeous bifunctional activity is owing to that optimized charge distribution facilitates the intermediates transformation. Aqueous ZABs based on MCC manifests high peak power density of 452 mW cm−2 and durable cycling stability of 1640 h. Quasi‐solid‐state ZABs based on MCC also show satisfactory performances (175 mW cm−2, 105 h). This work provides the route to develop efficient and durable electrocatalyst for constructing ZABs with long lifespan and high‐power‐density.

Magnetic excitation in the hyperkagome antiferromagnet Mn3RhSi

In a paramagnetic state of a hyperkagome lattice antiferromagnet Mn3RhSi, magnetic diffuse scattering by magnetic short-range order is observed over a wide temperature range of approximately 500 K above the Néel temperature of 190 K. We have studied the magnetic excitation with a single crystal in a wide energy range from 0.3 to 140 meV by inelastic neutron scattering, where the prominent inelastic neutron-scattering signal is observed at Q=(2,0,0). The inelastic scattering intensity integrated for two of twelve magnon modes leads to a localized magnetic moment of about 5 μB per Mn site, although the long-range ordered magnetic moment is only 2.61 μB at 4 K. The result suggests that a large part of the magnetic moment does not order in Mn3RhSi, possibly due to the geometrical spin frustration of the hyperkagome lattice. Published by the American Physical Society 2024

Study on N2 selectivity of iron-manganese ore catalysts in NH3-SCR process

Natural iron-manganese ores exhibit a good deNOx activity at low temperatures after a simple treatment, but the reason for its low N2 selectivity requires further in-depth study. This work conducted deNOx performance and characterization tests on iron-manganese ore catalysts. Based on the experimental results, a simplified computational model of the iron-manganese ore catalyst (Fe2O3/MnO2 (110) surface) was constructed, and the density functional theory (DFT) method was used to investigate the mechanism of N2 formation in the NH3-SCR process. Fe and Mn in the iron-manganese ore play an important role in the deNOx activity, and NH3 forms the stable chemical adsorption on its surface, especially on the Fe site, where the adsorption capacity of NH3 is stronger than that of Mn site. The Fe site exhibits better ability than the Mn site in the dehydrogenation reaction of NH3. However, in a comprehensive comparison, the capability of iron-manganese ore catalyst to promote NH3 dehydrogenation is not high. In addition, the key NH2NO intermediate prefers to form on the Mn site over the Fe2O3/MnO2 (110) surface. Among them, the Mn site is better than the Fe site in promoting the decomposition of NH2NO intermediate to form N2. The study can further understand the microscopic mechanism of iron-manganese ore catalysts in N2 formation, which lays a foundation for improving the N2 selectivity of iron-manganese ore deNOx catalysts.

Effect of A-site cation doping on the catalytic oxidation of toluene over mullite catalyst GdMn2O5

Manganese-based mullite (AMn2O5) catalysts are promising for the catalytic oxidation of VOCs, with their oxidation reaction performance being tunable by modifying the composition of the A-site elements. In this work, various manganese-based mullite catalysts (Gd0.9X0.1Mn2O5, X =Sr, Ce, or Ca) with different A-site elements doping were prepared by the citric acid sol–gel method and applied to the catalytic oxidation of toluene. The activity tests indicated that the enhancement of catalytic performance by doping elements was in the order of Sr > Ce > Ca. Notably, the T90 of the Gd0.9Sr0.1Mn2O5 catalyst was 235.6 °C, a lower 37.8 °C than that of the GdMn2O5. Comprehensive characterization and density functional theory (DFT) simulations revealed that Sr doping facilitates the reduction of Mn4+ to Mn3+, increases the electron occupancy of the eg orbitals in octahedral Mn sites, and elevates the Mn-d band center, thus facilitating the adsorption and activation of O2. Additionally, the raised O-p band center caused by Sr doping enhances lattice oxygen mobility. In situ DRIFTS analysis indicated that the introduction of Sr at the A-site optimizes the toluene reaction pathway and accelerates the reaction rate. This work reveals that a simple A-site cation doping strategy can effectively regulate manganese-based mullite catalysts’ electronic structure and surface reaction activity, providing a feasible method for the large-scale preparation of manganese-based mullite catalysts with excellent catalytic performance.

Molten salt method for preparing Mn0.3Ru0.7O2 nanosheets as a superior bifunctional catalyst for rechargeable zinc-air batteries

Integrating components for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) while optimizing their electronic structure is an effective strategy for developing excellent bifunctional catalysts for rechargeable zinc-air batteries (ZABs). In this study, we successfully fabricated Mn0.3Ru0.7O2 nanosheets based on a solid solution oxide using a simple molten salt method. The Mn0.3Ru0.7O2 nanosheets exhibits abundant Ru and Mn sites through the Ru-O-Mn structure, which serve as excellent OER and ORR active centers. Experimental and theoretical studies validate the coccurrence of charge transefer between the Ru-O-Mn bond, modulating the valence state and d-band center of the Mn and Ru, thereby subsequently improving their ORR/OER intrinsic activity. Remarkably, the Mn0.3Ru0.7O2 nanosheets displays superior electropcatalytic performance with a charge/discharge voltage gap (ΔE) of only 0.59 V, which is the best among all reported counterpart catalysts. A rechargeable ZAB utilizing Mn0.3Ru0.7O2 nanosheets achieved a power density of 154 mW cm−2 and a specific capacity of 821 mA h g−1, surpassing that of the commercial Pt/C + RuO2 mixing catalyst. This study offers a new strategy for preparing highly active and durable bifunctional catalysts for rechargeable ZABs.

Unveiling the mechanistic synergy in Mn-doped NiO catalysts with atomic-burry structure: Enhanced CO oxidation via Ni-OH and Mn bifunctionality

The development of non-noble metal catalysts for low-temperature CO oxidation is a pivotal subject in various disciplines. In this study, an optimized Mn-doped NiO catalyst (Mn-NiO-0.5), prepared via aerosol pyrolysis with an equal molar ratio of Ni to Mn, demonstrates remarkable performance. It achieves an 82 % CO conversion at -20 °C and a 100 % conversion between 10 °C and 800 °C. The catalyst’s turnover frequency (TOF) for CO oxidation significantly surpasses that of previously reported noble-metal-based catalysts, underscoring its superior efficiency. Dynamic analyses suggest that the enhanced catalytic activity is a result of the unique atom burr structure, which presents an extensive surface area replete with abundant active sites. This structural feature is instrumental in maximizing the catalyst’s interaction with CO molecules. Experimental findings, corroborated by density functional theory (DFT) calculations, elucidate the mechanism of CO oxidation on the Mn-NiO-0.5 catalyst. The process is facilitated by the synergistic action of bimetallic sites, where the Ni–OH site acts as the primary adsorption point for CO. Subsequently, the CO is oxidized to bicarbonate through the interaction with the oxygen (O or O2) at adjacent Mn sites. This pioneering study introduces a paradigm-shifting insight: the effectiveness of non-noble metal oxide catalysts can now compete with, and in some cases, outperform their noble metal counterparts. This breakthrough is set to transform the industry, presenting a compelling alternative to conventional noble metal catalysts and propelling the evolution of state-of-the-art environmental conservation technologies.

Transformation of in-plane to out-of-plane anisotropy in MnBi alloy for permanent magnet application: a First-principles study

The low-temperature phase (LTP) MnBi exhibits remarkable ferromagnetic properties at room temperature. However, below its Curie temperature (TC\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${T}_{C}$$\\end{document}), a phase transition occurs around 613 K due to diffusion of Mn into interstitial sites, raising concerns about its structural and magnetic properties. Furthermore, the presence of in-plane anisotropy in LTP-MnBi alloy at low temperatures raises concerns about its suitability for use in permanent magnet applications, even at higher temperature. Therefore, this study examines the structural and magnetic properties of pure LTP-MnBi and its successive Ni-doped and Fe-substituted alloys using first-principles study based on density functional theory (DFT). To prevent Mn diffusion into interstitial sites, Ni doping is employed. Additionally, the incorporation of Ni successfully addresses the in-plane anisotropy issue in LTP-MnBi, transforming it into out-of-plane anisotropy. Moreover, we explored the potential advantages of substituting Fe for one of Mn site. This substitution aims to improve the observed dynamical instability in Ni-doped alloy and to further enhanced the magnetocrystalline anisotropy energy (MAE) of the material, resulting in an MAE of 3.21 MJ/m3, along with a TC\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${T}_{C}$$\\end{document} of 523 K. Therefore, the coexistence of high MAE and moderate TC\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${T}_{C}$$\\end{document} in the Mn0.5Fe0.5Bi–Ni alloy presents viable option for its application in permanent magnet technology.

Deep mineralization of bisphenol A via Cu–Mn spinel oxide nanospheres anchored N-doped carbon activated peroxymonosulfate

Fenton-like technology can efficiently remove recalcitrant pollutants, but developing catalytic oxidation system for deep mineralization of pollutants remains a challenge. Therefore, Cu–Mn spinel oxide nanospheres anchored N-doped carbon (CMO/NC) was prepared by a one-step calcination method and used to activate peroxymonosulfate (PMS) for efficient mineralization of bisphenol A (BPA). With the use of 0.5 g/L CMO/NC and 0.2 g/L PMS, the added BPA (50 mg/L) was completely degraded and deeply mineralized (nearly 95.2 %) in 9 min. The apparent first-order degradation rate constant k was 0.557 min−1, which was 61.9, 6.2 and 2.5 times than those in the systems of N-C/PMS (0.009 min−1), CuO/NC/PMS (0.09 min−1) and Mn3O4/NC/PMS (0.22 min−1). A comparison between the catalytic performances of CMO/NC catalysts prepared by changing the dosage of urea confirmed the catalysis synergism between Cu–Mn spinel oxides and N-C. A further comparison between the catalytic performances of CMO/NC catalysts prepared by varying the Cu/Mn molar ratio of the precursors showed that the synergy between Cu and Mn sites promoted the catalytic activity, with a synergistic effect factor of 1.8. XPS and H2-TPR characterizations proved that strong Cu-Mn interaction caused Mn species easier to donate electrons to PMS and Cu species easier to accept electrons from PMS. The degradation pathway and intermediate toxicity suggested that the system did not produce secondary pollution. Based on the results of EPR and capture experiments confirming that 1O2 was the major active species, a mechanism on PMS activation was proposed. Through investigations of continuous flow BPA wastewater removal, the influence of coexisting anions and catalyst cycling stability, it was clearly demonstrated that the present system had broad application prospects.

Microwave-induced dual-responsive spinel (CoxMn1-xFe2O4) target-triggered non-radical pathways of peroxymonosulfate: Superexchange interaction and synergistic mechanism

The efficient activation of peroxymonosulfate (PMS) and the directional selection of oxidation pathways are crucial for achieving efficient pollutant removal in advanced oxidation processes (AOPs). A composite activation method of a microwave-induced dual-responsive catalyst (Co0.4Mn0.6Fe2O4) with both dielectric and catalytic properties is proposed to successfully trigger the non-radical pathway of PMS for 100 % removal of pharmaceutical pollutant (diatrizoate, DTZ) in 6 min, which shows good resistance to environmental interference and cyclic stability, and lower electrical energy requirement. 1O2 and surface-bound reactive oxygen species (ROS) are the main ROSs responsible for non-radical oxidation, with a total contribution of 98 %. The superexchange effect of Co-Mn (Mn3++Co3+→Mn4++Co2+) induces the electron delocalization of Mn site, which promotes the adsorption of PMS, interfacial charge transfer, and surface-bound ROS generation. The "thermal and non-thermal" effects of microwaves accelerate electron transfer and 1O2 generation to further trigger non-radical pathways. This work provides new strategies for bifunctional catalyst design and directional triggering of non-radical pathways of PMS-AOPs.