Nowadays, the limited catalytic efficiency, metal leaching, and stability decrease during catalyst reuse hinder the heterogeneous catalysis application in water treatment. Moreover, the heterogeneous catalysis mechanism regarding novel sodium periodate (NaIO 4 )-based advanced oxidation process (AOP) is ambiguous. Herein, MgMn 2 O 4 spinel was synthesized through the co-precipitation method to test the NaIO 4 -based AOP’s mechanism. The morphological and physicochemical properties of MgMn 2 O 4 were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In this research, 0.1 g L −1 MgMn 2 O 4 activated 1 mM NaIO 4 to remove 10 μM bisphenol A (BPA) in 60 min without toxic iodine species generation and the acute toxicity decrease through radical (iodine active substances, IO 3 • ) and non-radical ( 1 O 2 , Manganese (IV)-oxo species) pathways by utilizing X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), radical quenching experiments, and methyl phenyl sulfoxide (PMSO)-based probing experiment. With tetrahedral Mg 2+ introduction and the Mn 2+ /Mn 3+ /Mn 4+ redox domination, the MgMn 2 O 4 shows high catalytic ability for NaIO 4 . To summarize, this research would extend the mechanism for the NaIO 4 -based advanced oxidation process.
This work reports a composite material consisting of MgMn 2 O 4 particles and multi-walled carbon nanotubes (MWCNTs) for aqueous magnesium ion batteries (AMIBs), which is prepared with electrochemical conversion method. The electrochemical conversion method has the advantages of easy accessibility, mild condition and small structural failure of electrode material. The obtained MgMn 2 O 4 /MWCNTs displays good surface integrity and structure stability, which improves electrochemical performance. Simultaneously, MWCNTs network serves as the pathways of Mg 2+ ions and electrons not only shorts the ion migration path but also enlarges the interface of electrode/electrolyte. The MgMn 2 O 4 /MWCNTs exhibites the advantages of high conductivity, large charge-discharge capacity and good rate performance. The obtained MgMn 2 O 4 /MWCNTs shows a high discharge capacity of 412.9 mAh g −1 at 50 mA g −1 , which is close to two times of that for the MgMn 2 O 4 obtained by sol-gel method, and the capacity retention is 73.3% after 1000 cycles at 1000 mA g −1 . In addition, the MgMn 2 O 4 /MWCNTs//AC system is firstly assembled, which displays a specific discharge capacity of 94.5 mA h g −1 at 50 mA g −1 . Furthermore, the relevant electrochemical mechanism of Mg 2+ ion insertion/extraction can be explained by the change of manganese valence, which is investigated with ex-situ XRD and XPS measurements. This work expands the compound method of high-performance electrode material for rechargeable aqueous magnesium ion battery.
Polyhedral MgMn₂O₄ nanozymes were synthesized through a solvothermal route followed by high-temperature calcination. Their particle size and morphology were precisely tailored by varying the precursor concentration. Decreasing the precursor dosage reduced the particle size from approximately 3 μm to 1 μm while simultaneously transforming the morphology from bispherical aggregates into well-defined polyhedra, accompanied by a gradual decrease in crystallinity. The optimized polyhedral MgMn₂O₄ nanozymes exhibited pronounced intrinsic oxidase-like activity, directly catalyzing the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxidized TMB (TMBox) without the addition of exogenous hydrogen peroxide (H₂O₂). Exploiting this intrinsic catalytic activity, an intelligent colorimetric sensing platform was developed for the sensitive determination of epinephrine in human urine. The proposed platform exhibited a linear detection range of 10–100 μM with limits of detection of 0.382 μM (UV–vis), 0.365 μM (smartphone RGB), 0.431 μM (smartphone grayscale), and 0.289 μM (SERS). Owing to its excellent stability, high sensitivity, and outstanding selectivity, the integrated sensing platform demonstrates considerable potential for practical point-of-care biosensing applications.
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