Rodríguez Nieto F J, Pasquale M A, Cabrera C R, Arvia A J
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-Consejo Nacional de Investigaciones Científicas y Técnicas, Sucursal 4, Casilla de Correo 16, 1900 La Plata, Argentina.
Langmuir. 2006 Dec 5;22(25):10472-82. doi: 10.1021/la0611716.
The topography of platinum electrodes produced by electrodeposition (19 to 200 mC cm-2) on highly oriented pyrolytic graphite (HOPG) under different potential modulations was investigated by atomic force microscopy, scanning tunneling microscopy, and H-atom electrosorption voltammetry. To modulate electrodeposition, (i) triangular potential cycling at 0.1 V s-1, (ii) a linear cathodic potential at 0.1 V s-1 and anodic potential step cycling, and (iii) square wave potential cycling at 5000 Hz were utilized. AFM and STM imaging showed that at lower platinum loading the HOPG surface was partially covered by a 3D sublayer of platinum. Electrodes produced by procedure (i) were made of faceted platinum aggregates of about 200 nm and nanoclusters in the range of 5-20 nm; those that resulted from procedure (ii) consisted of anisotropic aggregates of nanoclusters arranged as quasi-parallel domains. These electrodes from (i) and (ii) behaved as fractal objects. The electrodes resulting from procedure (iii) exhibited a flat surface that behaved as a Euclidean object. For all WEs, as the platinum loading was increased the HOPG surface was fully covered by a thin 3D layer of platinum aggregates produced by electrodeposition and coalescence phenomena. Large platinum loading led to electrodes with fractal geometry. Statistical parameters (root-mean-square height, skewedness, kurtosis, anisotropy, Abbot curve, number of protrusions and valleys, and fractal dimension) were obtained from the analysis of AFM and STM imaging data. Platinum electrodeposition coupled to either H-adatom formation for procedures (i) and (ii) or phonon dispersion for (iii) was involved in the surface atom rearrangements related to electrofaceting. The H-adatom electrosorption voltammetry data were used to evaluate the real electrode surface area via the voltammetric charge and to advance a tentative explanation of the contribution of the different crystallographic facets to the global electrochemical process dominated by weak H-Pt adsorption interactions.
通过原子力显微镜、扫描隧道显微镜和氢原子电吸附伏安法研究了在不同电位调制下，在高度取向热解石墨（HOPG）上通过电沉积（19至200 mC cm-2）制备的铂电极的形貌。为了调节电沉积，采用了以下方法：（i）以0.1 V s-1的速率进行三角电位循环；（ii）以0.1 V s-1的速率进行线性阴极电位和阳极电位阶跃循环；（iii）以5000 Hz的速率进行方波电位循环。原子力显微镜（AFM）和扫描隧道显微镜（STM）成像表明，在较低的铂负载量下，HOPG表面部分被铂的三维子层覆盖。通过方法（i）制备的电极由约200 nm的多面铂聚集体和5-20 nm范围内的纳米团簇组成；通过方法（ii）制备的电极由排列为准平行域的纳米团簇的各向异性聚集体组成。来自（i）和（ii）的这些电极表现为分形物体。通过方法（iii）制备的电极呈现出平坦的表面，表现为欧几里得物体。对于所有工作电极，随着铂负载量的增加，HOPG表面被电沉积和聚结现象产生的铂聚集体的薄三维层完全覆盖。高铂负载量导致具有分形几何形状的电极。通过对AFM和STM成像数据的分析获得了统计参数（均方根高度、偏度、峰度、各向异性、阿伯特曲线、凸起和凹谷数量以及分形维数）。对于方法（i）和（ii），铂电沉积与氢原子形成相关，对于方法（iii），铂电沉积与声子色散相关，这涉及到与电刻面相关的表面原子重排。氢原子电吸附伏安法数据用于通过伏安电荷评估实际电极表面积，并初步解释不同晶体面在由弱氢 - 铂吸附相互作用主导的全局电化学过程中的贡献。
