Unusual temperature effect on the stability of nickel anodes in molten carbonates
Unusual temperature effect on the stability of nickel anodes in molten carbonates
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DOI：
10.1016/j.electacta.2017.05.149
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发表时间：
2017-08
影响因子：
6.6
通讯作者：
K. Du;Kaiyuan Zheng;Zhigang Chen;Hua Zhu;F. Gan;Dihua Wang
中科院分区：
文献类型：
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作者：
K. Du;Kaiyuan Zheng;Zhigang Chen;Hua Zhu;F. Gan;Dihua Wang
在450 °C ~ 750 °C温度范围内，系统研究了Li_2CO_3-Na_2CO_3-K_2CO_3共晶熔融电解槽中镍阳极的稳定性。观察到一种不寻常的温度效应，涉及熔体中镍的临界活化-钝化转变温度为575 ° C;在阳极极化下，发现镍在低于575 °C时发生快速溶解，而其表面在高于该温度时变得钝化，并且通过将温度升高至750 °C进一步提高钝化膜的稳定性。在镍的表面形成一层黑色的氧化膜，延缓镍的阳极溶解。通过电化学测试结合X射线光电子能谱（XPS）和X射线衍射（XRD）表征，研究了氧化膜的组成、结构及其形成机理。镍的两种温度敏感氧化态（即，Ni（II）和Ni（III））。在较低温度下，Ni（III）与Li 2CO 3发生联合收割机结合，形成可溶性更强的LiNiO 2，且随温度升高，Ni（III）在膜中的含量急剧下降。因此，在高于575 °C的温度下，可以形成由NiO组成的稳定的保护膜。
The stability of nickel anode in a eutectic molten Li2CO3-Na2CO3-K2CO3electrolysis cell was systematically investigated over the temperature range of 450 °C to 750 °C. An unusual temperature effect was observed involving a critical activation-passivation transition temperature at 575 °C for the nickel in the melt; rapid dissolution of nickel was found to occur below 575 °C under anodic polarization, whereas its surface became passivated above this temperature, and the stability of the passivation film was further improved by increasing the temperature up to 750 °C. A blackish oxide film forms on nickel surfaces that retard the anodic dissolution of nickel. The composition and structure of the oxide film, as well as its formation mechanism, were studied by electrochemical measurements combined with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterization. Two temperature sensitive oxidation states of nickel (i.e., Ni(II) and Ni(III)) formed during the anodic polarization. Ni(III) tended to combine with Li2CO3to form the more soluble LiNiO2during anodic polarization at lower temperature, and its content in the film decreased dramatically with increasing temperature. Thus, a stable and protective film consisting of NiO can form at temperatures above 575 °C.