The electrochemical oxidation of gold nanoparticles (NPs) has been examined in HSO and acidified NaCl by combining multiple techniques including scanning electrochemical cell microscopy (SECCM) and electrochemical transmission electron microscopy (EC-TEM). Our findings provide novel insights into the intricate oxidation dynamics of Au NPs, which are determined by the interplay between passivation and dissolution. SECCM chronoamperometric measurements in the Cl containing electrolyte reveal distinct current peak events during the dissolution process. We attribute these events to delayed one-by-one NP dissolution following the rapid breakdown of the passive layer formed during the initial stages of anodic polarization, and exposure of the metallic gold core to Cl ions. Statistical analysis of these peak events further uncovers relationships between the applied potential and the distribution of the peak descriptors over time. The analysis of the charge consumed during each event indicates that NPs undergo partial dissolution interrupted by rapid re-passivation. As the potential increases, the peak current rises and the duration of the peak events decreases due to intensified dissolution and faster re-passivation. The onset time of the peak events displays a highly stochastic nature. EC-TEM measurements support these findings by confirming that Au NPs dissolve one-by-one at different time intervals and stages, revealing a core-shell structure during the dissolution process. The shell, which is more resistant, leads to a delayed, particle-by-particle dissolution once it is broken down. Quantification of the EC-TEM video allows recreating an equivalent current-time transient which presents peak events similar to these measured by SECCM. These findings contribute to our understanding of the complex and stochastic behavior of nanoparticle dissolution, which cannot be fully explained by traditional (macro) electrochemistry alone. The combination of SECCM and EC-TEM offers high potential to understand complex nanomaterial degradation pathways, essential for the design of durable electrocatalysts for electrochemical conversion and storage applications.

中文翻译：

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使用扫描电化学电池显微镜观察金的电化学沉积和溶解的微观视图 - 第二部分：恒电位溶解以及与原位 EC-TEM 的相关性


通过结合扫描电化学细胞显微镜 (SECCM) 和电化学透射电子显微镜 (EC-TEM) 等多种技术，在 HSO 和酸化 NaCl 中对金纳米颗粒 (NP) 的电化学氧化进行了研究。我们的研究结果为金纳米粒子复杂的氧化动力学提供了新的见解，这是由钝化和溶解之间的相互作用决定的。含 Cl 电解液中的 SECCM 计时电流测量揭示了溶解过程中不同的电流峰值事件。我们将这些事件归因于阳极极化初始阶段形成的钝化层快速分解以及金属金核暴露于 Cl 离子后，纳米粒子逐一延迟溶解。这些峰值事件的统计分析进一步揭示了施加的电位与峰值描述符随时间的分布之间的关系。对每个事件期间消耗的电荷的分析表明，纳米粒子经历了部分溶解，并被快速重新钝化中断。随着电位增加，峰值电流上升，并且由于溶解加剧和重新钝化更快，峰值事件的持续时间减少。峰值事件的发生时间表现出高度随机性。 EC-TEM 测量通过确认 Au NP 在不同的时间间隔和阶段逐一溶解来支持这些发现，揭示了溶解过程中的核壳结构。外壳的抵抗力更强，一旦被分解，就会导致逐个颗粒的延迟溶解。 EC-TEM 视频的量化允许重新创建等效的电流时间瞬态，该瞬态呈现与 SECCM 测量的峰值事件类似的峰值事件。 这些发现有助于我们理解纳米颗粒溶解的复杂和随机行为，而这种行为不能仅用传统（宏观）电化学来完全解释。 SECCM 和 EC-TEM 的结合为理解复杂的纳米材料降解途径提供了巨大的潜力，这对于设计用于电化学转换和存储应用的耐用电催化剂至关重要。