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For rechargeable aqueous Zn-ion batteries (ZIBs), MnO2 is a desirable cathode material because of its structural diversity and high theoretical capacity of ~308 mA h g−1. MnO2 materials' poor cycle life and inferior conductivity, however, continue to be key obstacles to their application in ZIBs. These problems are anticipated to be resolved by developing a nanocomposite system consisting of MnO2 and a carbon-based matrix. Herein, a series of graphite carbon-coated δ-MnO2 nanoparticles (denoted as GC-δ-MnO2-X; X = 1, 2, and 3) for ZIB cathode materials is prepared via a feasible redox route and varying the amount of KMnO4 (7, 8, and 9 mmol). Benefiting from the abundant active sites and boosted Zn2+ ion diffusion rate, the GC-δ-MnO2-2 nanoparticles (8 mmol KMnO4) display excellent capacity of 299.6 mA h g−1 at 0.3 A g−1 with good cycle stability (62% capacity retention after 1500 cycles at 2 A g−1), surpassing that of the GC-δ-MnO2-1 (7 mmol KMnO4) and GC-δ-MnO2-3 (9 mmol KMnO4) samples. Moreover, the constructed quasi-solid-state ZIBs based on the GC-δ-MnO2-2 cathode show respectable capacity of 194.3 mA h g−1 at 0.3 A g−1, as well as outstanding safe properties. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) based on tin (Sn) have shown great potential as materials for lithium storage, thanks to their ability to alleviate volume expansion due to the homogeneous distribution of Sn in a porous matrix framework. However, the weak mechanical strength of the porous Sn-MOF structure has been a major challenge, leading to pulverization during the discharging/charging process. To overcome this issue, we have developed a feasible strategy to strengthen the Sn-MOF mechanical properties by incorporating SiO 2 /GeO 2 nanoparticles during the synthesis process. The resulting composites of Sn-Si and Sn-Ge exhibited high energy density and long-term cycle stability, thanks to their synergistic effect in alloying and conversion reactions. Our density functional theory (DFT) calculations have revealed that the rigid SiO 2 /GeO 2 nanoparticles enhance the Sn-MOF mechanical properties, including Young's and shear moduli, which contribute to the long-term cycle stability of these composites.

Exploring high-efficiency and stable monolithic structured catalysts is vital for catalytic combustion of volatile organic compounds. Herein, we prepared a series of Pd/δ-MnO 2 nanoflower arrays monolithic integrated catalysts (0.01-0.07 wt% theoretical Pd loading) via the hydrothermal growth of δ-MnO 2 nanoflowers onto the honeycomb cordierite, which subsequently served as the carrier for loading the Pd nanoparticles (NPs) through the electroless plating route. Moreover, we characterized the resulting monolithic integrated catalysts in detail and evaluated their catalytic activities for toluene combustion, in comparison to the controlled samples including only Pd NPs loading and the δ-MnO 2 nanoflower arrays. Amongst all the monolithic samples, the Pd/δ-MnO 2 nanoflower arrays monolithic catalyst with 0.05 wt% theoretical Pd loading delivered the best catalytic performance, reaching 90% toluene conversion at 221°C at a gas hourly space velocity (GHSV) of 10,000 h -1 . Moreover, this sample displayed superior catalytic activity for o -xylene combustion under a GHSV of 10,000 h -1 . The monolithic sample with optimal catalytic activity also displayed excellent catalytic stability after 30 h constant reaction at 210 and 221°C., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Li, Liao, Ling, Ye, Liu, Zhang, He and Cheng.)