Summary
To analyze the effect of Co and Ni on hydrogen generation in water, the reactions of Mg and Al with water in CoCl2 and NiCl2 solutions are studied in terms of amount of H2 produced and rate of reaction. Mg rapidly reacts with water in CoCl2 and NiCl2, producing high amount of H2 without induction time. While there is a short induction time is detected for Al─H2O reaction in CoCl2 and NiCl2. In addition to the galvanic cell behavior of the Mg (Al)/Co (Ni) compounds formed, Co and Ni catalyze the hydrogen production reaction; however, the agglomeration of Co or Ni leads to a noticeable decrease in H2 production. The open‐circuit potential in CoCl2 and NiCl2 solutions after the addition of Mg or Al at ambient temperature shows an obvious change, coinciding with the initiation of the hydrogen generation process. Mg rapidly reacts with water in Co (Ac)2, CoSO4, Ni (Ac)2 and NiSO4 solutions as a consequence of its intrinsic metallic properties and of the formation of Co or Ni. The hydrogen production amount is lower (<200 ml g−1) in Co (NO3)2 and Ni (NO3)2, even after adding NaCl. No reaction occurs when adding Al in CoSO4, Co (Ac)2, Co (NO3)2, NiSO4, Ni (Ac)2, and Ni (NO3)2. The synergistic effect of Co, Ni, and anion ions in water affects the rate of Al or Mg corrosion and hydrogen generation.
Summary
A Fe2O3@C/Co3O4 hybrid composite anode is synthesized via a two‐step hydrothermal method in which the acetylene carbon black component serves as a conductive matrix and as an effective elastic buffer to relieve the stress from Fe2O3@C and Co3O4/C during the electrochemical testing. The crystallinity, structure, morphology, and electrochemical performance of the composites are systematically characterized. Galvanostatic charge/discharge measurements of Fe2O3@C/Co3O4 present the excellent rate performance and cyclic stability. Its reversible capacity reaches 1478 mAh·g−1 after 45 cycles, and it is equal to 1035 mAh·g−1 after 350 cycles at a current density of 200 mA·g−1. Furthermore, the changes after 30, 45, 60, 90, and 120 cycles are investigated. It is found that the electrochemical performance varies with the morphological change of the electrode surface. Correspondingly, the microstructure, cyclic voltammetry curves, and Nyquist plots significantly change as a consequence of cycling. The results of this study provide an understanding of the increased capacity and excellent cyclic performance of a new anodic material for Li‐ion batteries.
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