Scanning electrochemical cell microscopy (SECCM) has been used to explore structure-electrocatalytic activity relationships through high-resolution mapping of local activities of electrocatalysts. However, utilizing SECCM in strongly alkaline conditions presents a significant challenge due to the high wettability of the alkaline electrolyte leading to a substantial instability of the droplet in contact with the sample surface, and hence to unpredictable wetting and spreading of the electrolyte. The spreading phenomena in SECCM is confirmed by the electrochemical response of a free-diffusing redox probe and finite element method (FEM) simulations. Considering the significance of alkaline electrolytes in electrocatalysis, these wetting issues restrict the application of SECCM for electrocatalyst elucidation in highly alkaline electrolytes. We resolve this issue by incorporating a small percentage of polyvinylpyrrolidone (PVP) in the electrolyte inside the SECCM capillary to increase the surface tension of the electrolyte. To demonstrate successful wetting mitigation and stable SECCM mapping, we performed oxygen evolution reaction (OER) mapping on polycrystalline Pt by using 1 M KOH with an optimized PVP concentration. The OER activity maps correlated with the orientation of the exposed facets determined by electron backscatter diffraction and reveal different activities between Pt facets, hence confirming our methodology for exploring electrocatalytic activities in single facet scale in concentrated alkaline media. Interestingly, the maximum OER current density was highest for (110) and (111) which contradicts the activity trends in acidic electrolyte for which (100) is most active for the OER.

中文翻译：

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通过扫描电化学电池显微镜控制高碱性电解质中的表面润湿，以实现单面 Pt 析氧电催化活性图谱


扫描电化学细胞显微镜（SECCM）已被用于通过电催化剂局部活性的高分辨率绘图来探索结构-电催化活性关系。然而，在强碱性条件下使用 SECCM 提出了重大挑战，因为碱性电解质的高润湿性导致与样品表面接触的液滴显着不稳定，从而导致电解质的不可预测的润湿和扩散。自由扩散氧化还原探针的电化学响应和有限元法 (FEM) 模拟证实了 SECCM 中的扩散现象。考虑到碱性电解质在电催化中的重要性，这些润湿问题限制了 SECCM 在高碱性电解质中电催化剂阐明的应用。我们通过在 SECCM 毛细管内的电解质中加入少量的聚乙烯吡咯烷酮 (PVP) 以增加电解质的表面张力来解决这个问题。为了证明成功的润湿缓解和稳定的 SECCM 测绘，我们使用具有优化 PVP 浓度的 1 M KOH 对多晶 Pt 进行析氧反应 (OER) 测绘。 OER 活性图与电子背散射衍射确定的暴露面的方向相关，并揭示了 Pt 面之间的不同活性，从而证实了我们在浓碱性介质中探索单面规模电催化活性的方法。有趣的是，(110)和(111)的最大OER电流密度最高，这与酸性电解质中的活性趋势相矛盾，其中(100)对于OER最活跃。