Nickel (Ni) is an important catalytic metal that finds application in electrochemical energy technologies, such as alkaline water electrolyzers (AWEs) and alkaline fuel cells (AFCs). An essential property that determines nickel’s applicability in AWE and AFC technologies is its stability under operating conditions, i.e., performance at extreme potential (E) conditions and in the presence of reactive gases. However, the electrochemical and electrocatalytic behavior of nickel is not as well understood as that of noble electrocatalytic metals such as platinum. This lack of knowledge needs to be addressed prior to dedicating significant efforts to the design, fabrication, and characterization of Ni-based materials for electrochemical energy technologies. We report experimental data on the catalytic activity and corrosion behavior of polycrystalline Ni in the presence of different dissolved gases. Cyclic voltammetry (CV) and potentiodynamic polarization (PDP) measurements are conducted at room temperature in 0.10 M aqueous NaOH solution saturated with either N₂(diss), H₂(diss), or O₂(diss). CV measurements are performed using different potential scan rates in the regions of α-Ni(OH)₂ and NiOOH formation/reduction. PDP measurements are conducted in the same electrolyte and in the presence of different dissolved gases but over a much broader potential range (−0.40 V ≤ E ≤ 2.20 V) and at a very low potential scan rate (s = 0.10 mV s⁻¹) to achieve steady-state conditions. The influence of the state of the electrode’s surface (metallic versus oxidized) on the catalytic activity and corrosion behavior of nickel is also investigated by applying two different types of conditioning. The results demonstrate that the electrochemical behavior of Ni changes depending on the nature of the dissolved gas. The corrosion behavior is shown to depend on the polarization direction, thus the surface state of the electrode, and the nature of the dissolved gas. A graph, which is an extension of the Pourbaix diagram for Ni, summarizes the main interfacial and faradaic processes occurring at the surface of polycrystalline Ni in relation to the potential. The results and their analysis are expected to benefit renewable electrochemical energy technologies, such as alkaline water electrolyzers and fuel cells. In addition, they will serve as standards in electrochemical and electrocatalytic characterization of monocrystalline Ni materials and Ni-based nanomaterials.

Graphical abstract

中文翻译：

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中性和活性气体存在下多晶镍在碱性介质中的催化活性和腐蚀行为

镍（Ni）是一种重要的催化金属，可用于电化学能源技术，例如碱性水电解槽（AWE）和碱性燃料电池（AFC）。决定镍在AWE和AFC技术中的适用性的一项重要特性是其在工作条件下的稳定性，即在极端电势下的性能（E）条件和有反应性气体存在的情况。但是，镍的电化学和电催化行为不如贵金属的电催化金属如铂好。在投入大量精力用于电化学能源技术的镍基材料的设计，制造和表征之前，需要解决这种知识不足的问题。我们报告了在不同溶解气体存在下多晶镍的催化活性和腐蚀行为的实验数据。循环伏安法（CV）和电势极化（PDP）测量是在室温下于0.10 M NaOH溶液中进行的，该溶液用N ₂（diss），H ₂（diss）或O ₂饱和（diss）。使用α-Ni（OH）₂和NiOOH形成/还原区域中的不同电位扫描速率执行CV测量。PDP测量是在相同的电解质和在不同溶解气体的存在，但在宽得多的电势范围（-0.40 V≤进行Ë ≤2.20 V）和以非常低的电势扫描速率（小号= 0.10毫伏小号^-1）以达到稳态条件。电极表面状态（金属与氧化态）对镍的催化活性和腐蚀行为的影响也通过应用两种不同的调节方法进行了研究。结果表明，Ni的电化学行为根据溶解气体的性质而变化。腐蚀行为取决于极化方向，电极的表面状态和溶解气体的性质。图是Ni的Pourbaix图的扩展，总结了与电势相关的多晶Ni表面上发生的主要界面和法拉第过程。结果及其分析有望使可再生电化学能源技术受益，例如碱性水电解槽和燃料电池。另外，它们将作为单晶镍材料和镍基纳米材料的电化学和电催化表征的标准。

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