Kim Jutae, Urchaga Patrick, Baranton Stève, Coutanceau Christophe, Jerkiewicz Gregory
Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, ON K7L 3N6, Canada.
Phys Chem Chem Phys. 2017 Aug 23;19(33):21955-21963. doi: 10.1039/c7cp02528a.
The electrochemical quartz-crystal nanobalance (EQCN) measures in situ mass changes associated with interfacial electrode processes. Real electrodes are not atomically flat, thus their surface roughness affects the conversion of frequency variations (Δf) to mass changes (Δm) associated with electrochemical processes. Here, we analyze Δm associated with the electrochemical H adsorption/desorption and surface oxide formation/reduction on Pt electrodes of gradually increasing surface roughness using the EQCN and cyclic-voltammetry in an aqueous HSO solution. These two interfacial processes are ideal to probe changes in the electrochemically active surface area. The surface roughness of Pt-coated resonators is fine-tuned through Pt electrodeposition and examined using atomic force microscopy. The results acquired using Pt electrodes of increasing roughness factor (1.61 ≤ R ≤ 13.0) reveal a linear relationship between Δm and R. Extrapolation of this relationship to R = 1.00 leads to the determination of Δm associated with H adsorption/desorption and oxide formation/reduction on an atomically flat polycrystalline Pt electrode. The values of Δm associated with these processes are analyzed in terms of the number of H, O, water, and ionic species interacting with each Pt atom of the electrode surface. We find that the charge densities associated with these electrochemical processes and mass variations do not scale up by the same factor. This leads to a modified version of the Sauerbrey equation for Pt electrodes, which takes into account the intrinsic surface roughness.
电化学石英晶体微天平（EQCN）可原位测量与界面电极过程相关的质量变化。实际电极并非原子级平整，因此其表面粗糙度会影响与电化学过程相关的频率变化（Δf）到质量变化（Δm）的转换。在此，我们使用EQCN和循环伏安法，在HSO水溶液中分析了表面粗糙度逐渐增加的铂电极上与电化学氢吸附/脱附和表面氧化物形成/还原相关的Δm。这两个界面过程是探测电化学活性表面积变化的理想选择。通过铂电沉积对涂铂谐振器的表面粗糙度进行微调，并使用原子力显微镜进行检测。使用粗糙度因子不断增加（1.61≤R≤13.0）的铂电极获得的结果显示，Δm与R之间存在线性关系。将这种关系外推到R = 1.00，可确定与原子级平整的多晶铂电极上的氢吸附/脱附和氧化物形成/还原相关的Δm。根据与电极表面每个铂原子相互作用的氢、氧、水和离子物种的数量，分析了与这些过程相关的Δm值。我们发现，与这些电化学过程和质量变化相关的电荷密度并非按相同因子放大。这导致了一个考虑了固有表面粗糙度的铂电极Sauerbrey方程的修正版本。
