Metal (oxy)hydroxides (MO_xH_y, M = Fe, Co, Ni, and mixtures thereof) are important materials in electrochemistry. In particular, MO_xH_y 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 Ni_1−δCo_δO_xH_y 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 NiO_xH_y 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 NiO_xH_y, which dramatically reorganize under electrochemical conditions to form nanoparticle assemblies, restructuring is not found for Ni_1−δCo_δO_xH_y with a high Co content. Ni_0.8Fe_0.2O_xH_y 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 MO_xH_y materials and provide insight into how nanostructure and composition affect structural dynamics at the nanoscale.

中文翻译：

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氧释放反应过程中金属（羟基）氢氧化物纳米片的结构演变

金属（氧）氢氧化物（MO _x H _y，M = Fe，Co，Ni及其混合物）是电化学中的重要材料。特别地，MO _x H _y是在碱性介质中最快的氧释放反应（OER）已知催化剂。尽管已经充分表征了诸如过电势和活性之类的关键特征，但尚未完全了解纳米结构及其在电化学条件下的动力学。在这里，我们对Ni的结构演进报告_1-δ钴_δ ø _X ħ _ý纳米片具有不同的Ni的比例对Co，在电化学循环期间使用operando原子力显微镜。我们发现在NiO中添加Co_x H _y纳米片会导致合成后的纳米片具有更高的孔隙率，从而明显降低了与氧化还原循环相关的机械应力，从而增强了在电化学条件下的稳定性。相对于纯的NiO构成的纳米片_X ħ _ÿ，其电化学的条件来形成纳米颗粒组装下急剧重组，重组未找到的Ni _1-δ钴_δ ø _X ħ _Ÿ具有高Co含量。镍_0.8铁_0.2 O _x H _y纳米片表现出高的合成粗糙度，其在电化学循环期间增加，同时保持了纳米片形状的完整性。这些发现增强了对MO _x H _y材料的基本理解，并提供了有关纳米结构和组成如何影响纳米级结构动力学的见识。