Structural Evolution of Metal (Oxy)hydroxide Nanosheets during the Oxygen Evolution Reaction
Structural Evolution of Metal (Oxy)hydroxide Nanosheets during the Oxygen Evolution Reaction
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DOI：
10.1021/acsami.8b02796
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发表时间：
2019-02-13
影响因子：
9.5
通讯作者：
Boettcher, Shannon W.
中科院分区：
文献类型：
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作者：
Dette, Christian;Hurst, Michael R.;Boettcher, Shannon W.
金属（氧）氢氧化物（MOxHy，M = Fe、Co、Ni及其混合物）是电化学中的重要材料。特别地，MOxHy是已知的用于碱性介质中的析氧反应（OER）的最快催化剂。虽然关键的描述符，如过电位和活性已被彻底表征，但纳米结构及其在电化学条件下的动力学尚未完全理解。在这里，我们报告的结构演变的Ni 1-δ Co δ OxHy纳米片与不同比例的Ni，Co，在operando在电化学循环过程中使用原子力显微镜。我们发现，添加Co到NiOxHy纳米片导致合成的纳米片的更高的孔隙率，明显降低了与氧化还原循环相关的机械应力，从而提高了电化学条件下的稳定性。与由纯NiOxHy组成的纳米片相反，纯NiOxHy在电化学条件下显著重组以形成纳米颗粒组装体，未发现具有高Co含量的Ni 1-δ Co δ OxHy的重组。Ni0.8Fe0.2OxHy纳米片显示出合成的高粗糙度，其在电化学循环期间增加，同时保持纳米片形状的完整性。这些发现增强了对MOxHy材料的基本理解，并提供了对纳米结构和组成如何影响纳米尺度结构动力学的见解。
Metal (oxy)hydroxides (MOxHy, M = Fe, Co, Ni, and mixtures thereof) are important materials in electrochemistry. In particular, MOxHy are the fastest known catalysts for the oxygen evolution reaction (OER) in alkaline media. While key descriptors such as overpotentials and activity have been thoroughly characterized, the nanostructure and its dynamics under electrochemical conditions are not yet fully understood. Here, we report on the structural evolution of Ni1-delta Co delta OxHy nanosheets with varying ratios of Ni to Co, in operando using atomic force microscopy during electrochemical cycling. We found that the addition of Co to NiOxHy nanosheets results in a higher porosity of the as synthesized nanosheets, apparently reducing mechanical stress associated with redox cycling and hence enhancing stability under electrochemical conditions. As opposed to nanosheets composed of pure NiOxHy, which dramatically reorganize under electro-chemical conditions to form nanoparticle assemblies, restructuring is not found for Ni1-delta Co delta OxHy with a high Co content. Ni0.8Fe0.2OxHy nanosheets show high roughness as synthesized which increases during electrochemical cycling while the integrity of the nanosheet shape is maintained. These findings enhance the fundamental understanding of MOxHy materials and provide insight into how nanostructure and composition affect structural dynamics at the nanoscale.