Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg , 93053 Regensburg, Germany.
Anal Chem. 2017 Feb 7;89(3):1658-1664. doi: 10.1021/acs.analchem.6b03764. Epub 2017 Jan 18.
In the present report the well-known advantages of hydrodynamic mass transport in electrochemical systems are used in combination with scanning electrochemical microscopy (SECM). The hydrodynamic SECM system integrates a high-precision stirring device into the experimental setup. The well-defined stirring of the SECM electrolyte results in steady state diffusion layer characteristics in the vicinity of large substrate electrodes operated in chronoamperometric measuring mode. For a range of rotation frequencies of a rotating cylinder the thickness and the stability of the diffusion layer was studied by hydrodynamic SECM in the substrate generation/tip collection (SG/TC) as well as in the competition mode using ferrocene methanol as redox mediator. Different UME probe dimensions ranging from Pt diameters of 20 μm down to 0.6 μm were used. The smallest probe with d = 0.6 μm was found most suitable for these studies due to the almost convection-independent amperometric response associated with subμm electrodes. Additionally, preliminary studies of hydrodynamic SECM imaging of a 2 mm Pt disk electrode surface in the SG/TC mode based on in situ produced hydrogen as a mediator are presented. Comparative images measured in the conventional positive feedback mode in quiescent solution show that hydrodynamic SECM offers attractive complementary information.
在本报告中，将电化学系统中众所周知的流体动力质量传输优势与扫描电化学显微镜（SECM）结合使用。该流体动力 SECM 系统将高精度搅拌装置集成到实验设置中。在chronoamperometric 测量模式下，在大基底电极附近，SECM 电解液的明确定义搅拌导致扩散层特性达到稳定状态。在旋转圆柱的一系列旋转频率下，使用 ferrocene methanol 作为氧化还原介体，通过基底生成/尖端收集 (SG/TC) 以及竞争模式下的流体动力 SECM 研究了扩散层的厚度和稳定性。使用的 UME 探针尺寸范围从 20 μm 的 Pt 直径减小到 0.6 μm。由于与亚微米电极相关的几乎与对流无关的安培响应，最小的 d=0.6 μm 的探针被发现最适合这些研究。此外，还提出了基于原位产生的氢气作为介体的 SG/TC 模式下 2mm Pt 圆盘电极表面的流体动力 SECM 成像的初步研究。在静止溶液中以传统正反馈模式测量的比较图像表明，流体动力 SECM 提供了有吸引力的互补信息。
