Sodium-Selenium Batteries with Outstanding Rate Capability by Introducing Cubic Mn2 O3 Electrocatalyst.

With their high volumetric capacity and electronic conductivity, sodium-selenium (Na-Se) batteries have attracted attention for advanced battery systems. However, the irreversible deposition of sodium selenide (Na2 Se) results in rapid capacity degradation and poor Coulombic efficiency. To address these issues, cubic α-Mn2 O3 is introduced herein as an electrocatalyst to effectively catalyze Na2 Se conversion and improve the utilization of active materials. The results show that the addition of 10 wt% Mn2 O3 in the selenium/Ketjen black (Se/KB) composite enhances the conversion from Na2 Se to Se by lowering activation energy barrier and leads to fast sodium-ion kinetics and low internal resistance. Consequently, the Mn2 O3 -based composite delivers a high specific capacity of 635 mAh ⋅ g-1 at 675 mA ⋅ g-1 after 250 cycles as well as excellent cycling stability for 800 cycles with a high specific capacity of 317 mAh ⋅ g-1 even at the high current density of 3375 mA ⋅ g-1 . Due to the cubic Mn2 O3 electrocatalyst, the performance of the composites is superior to existing state-of-the-art Na-Se batteries reported in the literature.

Morphological, microstructural and photocatalytic characterization of undoped and Ni, Co doped Fe2O3 particles synthesized by sonochemical method.

In this study, an abundant and eco-friendly photocatalytic material, Fe2O3 particles were synthesized by sonochemical method. Morphological and microstructural investigations of synthesized undoped and Ni, Co-doped Fe2O3 particles were performed. The effect of particle morphology and microstructure on its photocatalytic performance was further investigated. Comparative studies for evaluating particle crystallite sizes were conducted by Williamson-Hall (W-H) method and modified Debye-Scherrer (MDS). Crystallite sizes and lattice strains of Fe2O3 induced by process parameters were calculated by W-H method based on uniform deformation model (UDM). The crystallite sizes of the synthesized powders were calculated in the range of 200 nm and 76 nm by Williamson-Hall analysis. In addition to structural investigation, dislocation density of the synthesized particles was calculated by Williamson-Smallman relation. Afterwards, photocatalytic performance of Fe2O3 particles was investigated in detail. The photodegradation of methylene blue solutions in the presence of light in 20 min with samples 3,4, and 5 in 20 min were 0.937, 0.896, and 0.855, respectively. Moreover, the photodegradation of methylene blue solution with sample 5 for 15, 30, and 45 min were 0.9, 0.828, and 0.757, respectively. A photocatalytic activity of 24.25% has been observed under optimum conditions for the time interval of 45 min.