No abstract

Rechargeable Li-O2 batteries have been considered as the most promising chemical power owing to their ultrahigh specific energy density. But the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) result in the high overpotential (~1.5V), the poor rate capability and even the short cycle life, which critically hinder their practical applications. Herein, we propose a synergistic strategy to boost the electrocatalytic activity of Co3O4 nanosheets for Li-O2 battery by tuning the inner oxygen vacancies and the exterior Co 3+ /Co 2+ ratio which have been identified by Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray Absorption Near Edge Structure spectroscopy. Operando X-ray diffraction and ex-situ Scanning Electron Microscope are used to probe the evolution of the discharge product. In comparison with bulk Co3O4, the cells catalyzed by Co3O4 nanosheets show a much higher initial capacity (~24051.2mAh g -1 ), better rate capability (8683.3mAh g -1 @400mA g -1 ) and cycling stability (150 cycles@400mA g -1 ), and lower overpotential. The large enhancement of the electrochemical performances can be greatly attributed to the synergistic effect of the architectured 2D nanosheets, the oxygen vacancies and Co 3+ /Co 2+ difference between the surface and the interior.Moreover, the addition of LiI in the electrolyte can further reduce the overpotential making the battery more practical. This study offers some insights into designing high performance electrocatalysts for Li-O2 batteries through the combination of the 2D nanosheets architecture, oxygen vacancy and surface electronic structure regulation.

A substantial knowledge on the pathogenesis of diabetes mellitus (DM) by oxidative stress and inflammation is available. Berberine is a biologically active botanical that can combat oxidative stress and inflammation and thus ameliorate DM, especially type 2 DM. This article describes the potential of berberine against oxidative stress and inflammation with special emphasis on its mechanistic aspects. In diabetic animal studies, the modified levels of proinflammatory cytokines and oxidative stress markers were observed after administering berberine. In renal, fat, hepatic, pancreatic and several others tissues, berberine-mediated suppression of oxidative stress and inflammation was noted. Berberine acted against oxidative stress and inflammation through a very complex mechanism consisting of several kinases and signaling pathways involving various factors, including NF-κB (nuclear factor-κB) and AMPK (AMP-activated protein kinases). Moreover, MAPKs (mitogen-activated protein kinases) and Nrf2 (nuclear factor erythroid-2 related factor 2) also have mechanistic involvement in oxidative stress and inflammation. In spite of above advancements, the mechanistic aspects of the inhibitory role of berberine against oxidative stress and inflammation in diabetes mellitus still necessitate additional molecular studies. These studies will be useful to examine the new prospects of natural moieties against DM.