High-performance pseudocapacitive removal of cadmium via synergistic valence conversion in perovskite-type FeMnO3

Cadmium pollution is a serious threat for the global drink water and natural environment. Herein, a poly-pyrrole coated dual-metal perovskite-type oxide FeMnO₃ (PFMO@PPy) was developed firstly as pseudocapacitive cathode for the reversible capture and release of cadmium ions by asymmetry pseudocapacitive deionization (APCDI) technology, extending the library of CDI electrodes. Our work highlighted several points: (i) PFMO@PPy achieved a maximum Cd-removal capacity of 144.6 mg g^-1, and maintained the retention rate of 93.4% after 15-cycle CDI process for up to 150 h, far beyond other previous work. (ii) PFMO@PPy showed the superior removal ratio (~90%) under different real water environments such as tap water, lake water and the groundwater. (iii) The superior Cd(II) electrosorption and desorption behavior is ascribed to the reversible synergistic valence conversion (Fe³⁺/Fe⁰ and Mn³⁺/Mn²⁺), which is confirmed by ex-situ XPS measurement and electrochemical tests. (iv) DFT calculations confirmed the synergistic effect from Mn and Fe elements in perovskite-type bimetallic oxide FeMnO₃. This study paves a new way for promising future applications of perovskite-type oxides containing dual Faradic redox-activity for wastewater treatment and environmental remediation.

Co-Existence of Iron Oxide Nanoparticles and Manganese Oxide Nanorods as Decoration of Hollow Carbon Spheres for Boosting Electrochemical Performance of Li-Ion Battery

Here, we report that mesoporous hollow carbon spheres (HCS) can be simultaneously functionalized: (i) endohedrally by iron oxide nanoparticle and (ii) egzohedrally by manganese oxide nanorods (FexOy/MnO2/HCS). Detailed analysis reveals a high degree of graphitization of HCS structures. The mesoporous nature of carbon is further confirmed by N2 sorption/desorption and transmission electron microscopy (TEM) studies. The fabricated molecular heterostructure was tested as the anode material of a lithium-ion battery (LIB). For both metal oxides under study, their mixture stored in HCS yielded a significant increase in electrochemical performance. Its electrochemical response was compared to the HCS decorated with a single component of the respective metal oxide applied as a LIB electrode. The discharge capacity of FexOy/MnO2/HCS is 1091 mAhg-1 at 5 Ag-1, and the corresponding coulombic efficiency (CE) is as high as 98%. Therefore, the addition of MnO2 in the form of nanorods allows for boosting the nanocomposite electrochemical performance with respect to the spherical nanoparticles due to better reversible capacity and cycling performance. Thus, the structure has great potential application in the LIB field.

All-Inorganic p-n Heterojunction Solar Cells by Solution Combustion Synthesis Using N-type FeMnO3 Perovskite Photoactive Layer

This study outlines the synthesis and physicochemical characteristics of a solution-processable iron manganite (FeMnO₃) nanoparticles via a chemical combustion method using tartaric acid as a fuel whilst demonstrating the performance of this material as a n-type photoactive layer in all-oxide solar cells. It is shown that the solution combustion synthesis (SCS) method enables the formation of pure crystal phase FeMnO₃ with controllable particle size. XRD pattern and morphology images from TEM confirm the purity of FeMnO₃ phase and the relatively small crystallite size (∼13 nm), firstly reported in the literature. Moreover, to assemble a network of connected FeMnO₃ nanoparticles, β-alanine was used as a capping agent and dimethylformamide (DMF) as a polar aprotic solvent for the colloidal dispersion of FeMnO₃ NPs. This procedure yields a ∼500 nm thick FeMnO₃ n-type photoactive layer. The proposed method is crucial to obtain functional solution processed NiO/FeMnO₃ heterojunction inorganic photovoltaics. Photovoltaic performance and solar cell device limitations of the NiO/FeMnO₃-based heterojunction solar cells are presented.

The encapsulation of MnFe2O4 nanoparticles into the carbon framework with superior rate capability for lithium-ion batteries

Binary transition metal oxides (BTMOs) have been regarded as one of the most hopeful anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity, excellent electrochemical activity and abundant electrochemical reactions. However, BTMOs still suffer from two main problems, which are poor conductivity and large volume expansion during the charge/discharge processes. In order to address the above-mentioned problems, mesoporous MnFe2O4@C nanorods have been successfully synthesized in this work. The synergistic effect of the cross-linked carbon framework and mesoporous structure greatly improves the electrochemical performances. As expected, the mesoporous MnFe2O4@C electrode manifests discharge capacities of 987.5 and 816.6 mA h g-1 at the current densities of 100 and 2000 mA g-1, respectively, with the capacity retention ratio of 82.7%, exerting distinguished rate capabilities for LIBs.

Synthesis and antibacterial activity of iron manganite (FeMnO3) particles against the environmental bacterium Bacillus subtilis

Iron manganite (FeMnO₃) particles express antibacterial activity against Bacillus subtilis, together with H₂O₂ release and Fe, Mn-ion release in LB bacterial medium.

Nonhierarchical Heterostructured Fe2 O3 /Mn2 O3 Porous Hollow Spheres for Enhanced Lithium Storage

High capacity transition-metal oxides play significant roles as battery anodes benefiting from their tunable redox chemistry, low cost, and environmental friendliness. However, the application of these conversion-type electrodes is hampered by inherent large volume variation and poor kinetics. Here, a binary metal oxide prototype, denoted as nonhierarchical heterostructured Fe₂ O₃ /Mn₂ O₃ porous hollow spheres, is proposed through a one-pot self-assembly method. Beyond conventional heteromaterial, Fe₂ O₃ /Mn₂ O₃ based on the interface of (104)_Fe2O3 and (222)_Mn2O3 exhibits the nonhierarchical configuration, where nanosized building blocks are integrated into microsized spheres, leading to the enhanced structural stability and boosted reaction kinetics. With this design, the Fe₂ O₃ /Mn₂ O₃ anode shows a high reversible capacity of 1075 mA h g^-1 at 0.5 A g^-1 , an outstanding rate capability of 638 mA h g^-1 at 8 A g^-1 , and an excellent cyclability with a capacity retention of 89.3% after 600 cycles.