Amorphous hierarchical porous manganese oxides for supercapacitors with excellent cycle performance and rate capability

An Amorphous-Crystalline Nanosheet Arrays Structure for Ultrahigh Electrochemical Performance Supercapattery

Hybrid supercapacitors (HSCs), also called supercapattery, which can substitute for low power density batteries have attracted extensive interest. However, when HSCs comes to commercial applications, there is still space for improvement in energy density. It seems that designing of electrode with high capacity is an effective measure. Herein, amorphous-crystalline MoO₃ -Ni₃ S₂ /NF-0.5 nanosheet arrays are developed as battery-type electrodes. Specifically, the sheet-like structure of crystalline Ni₃ S₂ can achieve rich structural nanocrystallization, improving the redox reaction efficiency. Meanwhile, the disordered structure and irregular surface of the amorphous MoO₃ are conducive to maximize the contact between the electrode and electrolyte, slowing down the volume change caused by the continuous charge-discharge process. As a result, it displays an ultrahigh areal specific capacity of 8.52 C cm^-2 at 5 mA cm^-2 , and superior lifespan up to 7500 cycles with 90.0% retention. Further, when assembled into HSCs, the specific capacity reaches 1.47 C cm^-2 , corresponding to an energy density of 4.18 mWh cm^-2 at a power density of 0.34 mW cm^-2 . Totally, the design of the unique structure displays a valuable measure for rational development of high energy density hybrid energy storage devices that are not limited to supercapacitors.

Effects of preparation method and precipitant on Mn–Ga oxide in combination with SAPO-34 for syngas conversion into light olefins

Mn–Ga oxides were prepared by different methods and using different precipitants, and the co-precipitated Mn–Ga using NH₃·H₂O as a precipitant exhibits the best performance.

Facile synthesis of manganese oxide modified lignin nanocomposites from lignocellulosic biorefinery wastes for dye removal

In this study, a facile method to prepare MnO₂ nanodots modified lignin nanocomposite (MnO₂@LNP) was developed for efficient dye removal. The MnO₂@LNP displayed hierarchical spherical nanostructures, where the MnO₂ nanodots were evenly dispersed within the lignin nanosphere. Compared with lignin nanoparticles, the as-prepared MnO₂@LNP exhibits higher surface area and can be separated after adsorption. It showed excellent adsorption capacity (806 mg/g) towards a typical cationic dye, methylene blue (MB), at a fast removal rate, where more than 80% of adsorption capacity was reached within 5 min at room temperature. The high adsorption capacity was contributed by the high surface area and negative charge on the adsorbent. The adsorption process is pH-responsive and exothermic, and the spent adsorbent can be reused for at least five cycles. This study displayed an efficient method to prepare MnO₂@LNP for the high-value utilization of lignin-derived from lignocellulosic biorefinery.

Amorphous manganese oxide as highly active catalyst for soot oxidation

A series of highly active amorphous manganese oxide catalysts for soot combustion were synthesized using colloidal solution combustion synthesis (CSCS) method. The surface morphological and structural properties were systematically tested via various techniques: X-ray diffraction, N₂ adsorption-desorption, temperature-programmed reduction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Manganese precursors and calcination temperatures affect the crystal structure, redox properties, and surface properties of MnOx. With the calcination temperature increasing from 550 to 850 °C, the crystalline structure of manganese oxides changed from amorphous phase to crystal phase. In general, the amorphous MnOx with a hierarchical porous structure showed better catalytic activity for soot oxidation than the crystal ones (T₁₀ as indicator), which can be ascribed to the improved low-temperature reducibility, more surface active oxygen species, and abundant surface Mn⁴⁺ ions. The presence of NO in O₂ also promoted soot oxidation which follows the NO₂-assisted mechanism. Our work may provide a rational comparison between high-efficient amorphous and crystal MnOx catalysts for soot oxidation.