从理论和实验上改进的电化学相图：Ni-水系统及其复杂化合物,The Journal of Physical Chemistry C

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从理论和实验上改进的电化学相图：Ni-水系统及其复杂化合物
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-05-01 00:00:00 , DOI: 10.1021/acs.jpcc.7b02771
L.-F. Huang ₁ , M. J. Hutchison ₂ , R. J. Santucci ₂ , J. R. Scully ₂ , J. M. Rondinelli ₁

Affiliation

电极电势-pH（Pourbaix）图提供了金属中最稳定的化合物，其腐蚀产物以及溶液中相关离子的相图。这些相图的实用性在于它们能够评估电化学稳定性，例如镍金属及其衍生的氧化物，氢氧化物和羟基氧化物在水环境中对腐蚀的电化学稳定性。值得注意的是，过去50年间报道的Ni Pourbaix图在很大程度上与各种电化学观察结果不一致，这可能归因于用于生成可用图的复杂Ni基化合物的实验形成自由能（_ΔfG）不准确。在这里，我们证明了最新的密度泛函理论（DFT）可用于获得准确的_ΔfG值导致产生的Ni Pourbaix图与直接电化学实验更加一致：电化学阻抗谱和表面增强拉曼光谱用于表征NiO和在Ni上形成的Ni（OH）₂的电化学稳定性，从而证明了Ni的可靠性。基于无校正的第一性原理的Pourbaix图。我们的结果表明，在结合现代密度泛函功能和水环境化合物鉴定实验进展以评估材料的电化学相稳定性方面的重要性，这将对耐腐蚀金属，光吸收剂和光催化材料的设计，合成和选择非常有用材料。

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Improved Electrochemical Phase Diagrams from Theory and Experiment: The Ni–Water System and Its Complex Compounds

Electrode potential–pH (Pourbaix) diagrams provide a phase map of the most stable compounds of a metal, its corrosion products, and associated ions in solution. The utility of these phase diagrams is that they enable the assessment of electrochemical stabilities, for example, of Ni metal and its derived oxides, hydroxides, and oxyhydroxides, against corrosion in aqueous environments. Remarkably, the Ni Pourbaix diagrams reported over the last 50 years are largely inconsistent with various electrochemical observations, which may be attributed to inaccurate experimental free energies of formation (Δ_fG) for the complex Ni-based compounds used in producing the available diagrams. Here we show that state-of-the-art density-functional theory (DFT) can be used to obtain accurate Δ_fG values, which lead to Ni Pourbaix diagrams that are more consistent with direct electrochemical experiments: Electrochemical impedance spectroscopy and surface-enhanced Raman spectroscopy are used to characterize the electrochemical stabilities of NiO and Ni(OH)₂ formed on Ni, demonstrating the reliability in correction-free first-principles based Pourbaix diagrams. Our results show the importance in applying modern density functionals in combination with experimental advances in aqueous environment compound identification for assessing electrochemical phase stability of materials, which will be useful for the design, synthesis, and selection of corrosion-resistant metals, photoabsorbers, and photocatalytic materials.

更新日期：2017-05-01

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