Therapy with the probiotic bacteria B. Subtilis and E. faecalis are an effective and safe means for preventing VAP and the acquisition of PPMO colonization in the stomach.

Noble-metal-free bifunctional cathode catalysts, which can promote both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), are quite necessary for lithium−air batteries. In this study, we propose a novel strategy to improve the catalytic performance of CoO through the integration with the dotted carbon species and oxygen vacancies. We have successfully prepared carbon-dotted defective CoO with oxygen vacancies (CoO/C) by sintering the pink precursors obtained from the ethanol-mediated Co(Ac) 2 •4H 2 O. In comparison with the commercial or oxygen-vacancies-only CoO, the cycling stability, the initial capacity, and the rate capability of CoO/C-catalyzed cathode have all been greatly enhanced, and the overpotential has also been decreased, which can be attributed to the synergetic effect of the dotted carbon species and oxygen vacancies on both ORR and OER. Oxygen vacancies can enhance the mobility of e − and Li + and bind to O 2 and Li 2 O 2 as active sites. The dotted carbon species not only improve the conductivity of CoO but also stabilize the oxygen vacancies during ORR/OER. In addition, our further investigation on the evolution of the morphology and phase composition of CoO/C and commercial CoO based cathodes under different charge/discharge states confirms that CoO/ C can largely accelerate the formation and decomposition of Li 2 O 2 during discharge−charge cycles.

Co substitution has been extensively used to improve the electrochemical performances of cathode materials for sodium-ion batteries (SIBs), but the role of Co has not been well understood. Herein, we have comprehensively investigated the effects of Co substitution for Ni on the structure and electrochemical performances of Na0.7Mn0.7Ni0.3-xCoxO2 (x = 0, 0.1, 0.3) as cathode materials for SIBs. In comparison with the Co-free sample, the high-rate capability and cycle performance have been greatly improved by the substitution of Co, and some new insights into the role of Co have been proposed for the first time. With the substitution of Co(3+) for Ni(2+) the lattice parameter a decreases; however, c increases, and the d-spacing of the sodium-ion diffusion layer has been enlarged, which enhances the diffusion coefficient of the sodium ion and the high-rate capability of cathode materials. In addition, Co substitution shortens the bond lengths of TM-O (TM = transition metal) and O-O due to the smaller size of Co(3+) than Ni(2+), which accounts for the decreased thickness and volume of the TMO6 octahedron. The contraction of TM-O and O-O bond lengths and the shrinkage of the TMO6 octahedron improve the structure stability and the cycle performance. Last but not least, the aliovalent substitution of Co(3+) for Ni(2+) can improve the electronic conductivity during the electrochemical reaction, which is also favorable to enhance the high-rate performance. This study not only unveils the role of Co in improving the high-rate capability and the cycle stability of layered Na0.7Mn0.7Ni0.3-xCoxO2 cathode materials but also offers some new insights into designing high performance cathode materials for SIBs.

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