用布拉格相干衍射成像研究银纳米粒子在非吸附电解质中的稳定极限和表面化学
Stability Limits and Surface Chemistry of Ag Nanoparticles in Non-Adsorbing Electrolytes Probed by Bragg Coherent Diffractive Imaging
摘要：
表面化学在腐蚀和纳米结构合成等不同领域都很重要。不幸的是，许多合成的纳米材料，包括用于燃料电池的部分脱合金纳米颗粒催化剂，具有高活性表面，在其反应环境中不稳定，阻碍了广泛应用。因此，通过关注纳米尺度下的结构-稳定性和缺陷-稳定性关系来理解不稳定性是至关重要的，并且可能在应对重大挑战方面发挥重要作用。为此，最近的进展，在成像纳米结构的稳定性已经通过电子，X射线，和其他技术，如原子力显微镜，但往往限于特定的样品环境和/或二维图像。在这里，我们报告的缺陷稳定性关系的银纳米粒子的电压诱导的电化学溶解成像在三维（3D）的详细原位布拉格相干衍射成像（BCDI）的调查。我们首先通过固定探针旋转圆盘电极（SPRDE）结合电感耦合等离子体质谱（ICP-MS）确定平均溶解动力学，这允许实时原位测量Ag+离子形成和相应的电化学电流。然后，我们在单个纳米晶体中用BCDI观察3D溶解和再沉积过程，提供关于表面应变，缺陷及其与溶解化学的耦合作用的独特见解。开发的方法和获得的知识远远超出了“简单”的银电化学，并适用于所有的电催化反应的活性和稳定性之间的功能联系控制的结构和缺陷动力学。
英文摘要：
Surface chemistry is important across diverse fields such as corrosion and nanostructure synthesis. Unfortunately, many as-synthesized nanomaterials, including partially dealloyed nanoparticle catalysts for fuel cells, with highly active surfaces are not stable in their reactive environments, preventing widespread application. Thus, understanding instability by focusing on the structure-stability and defect-stability relationship at the nanoscale is crucial and will likely play an important role in meeting grand challenges. To this end, recent advances in imaging nanostructure stability have come via both electron, x-ray, and other techniques such as atomic force microscopy, but tend to be limited to specific sample environments and/or two-dimensional images. Here, we report investigations into the defect-stability relationship of silver nanoparticles to voltage-induced electrochemical dissolution imaged in-situ in three-dimensional (3D) detail by Bragg Coherent Diffractive Imaging (BCDI). We first determine the average dissolution kinetics by Stationary Probe Rotating Disk Electrode (SPRDE) in combination with inductively coupled plasma mass spectrometry (ICP-MS), which allows real-time in-situ measurement of Ag+ ions formation and the corresponding electrochemical current. We then observe the dissolution and redeposition processes in 3D with BCDI in single nanocrystals, providing unique insight about the role of surface strain, defects, and their coupling to the dissolution chemistry. The methods developed and the knowledge gained go well beyond a "simple" silver electrochemistry and are applicable to all electrocatalytic reactions where functional links between activity and stability are controlled by structure and defect dynamics.
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