Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden.
Phys Chem Chem Phys. 2018 Jun 27;20(25):17105-17116. doi: 10.1039/c8cp01814f.
Here, we report the electrochemical deposition of lead (Pb) as a model metal on epitaxial graphene fabricated on silicon carbide (Gr/SiC). The kinetics of electrodeposition and morphological characteristics of the deposits were evaluated by complementary electrochemical, physical and computational methods. The use of Gr/SiC as an electrode allowed the tracking of lead-associated redox conversions. The analysis of current transients passed during the deposition revealed an instantaneous nucleation mechanism controlled by convergent mass transport on the nuclei locally randomly distributed on epitaxial graphene. This key observation of the deposit topology was confirmed by low values of the experimentally-estimated apparent diffusion coefficient, Raman spectroscopy and scanning electron microscopy (SEM) studies. First principles calculations showed that the nucleation of Pb clusters on the graphene surface leads to weakening of the interaction strength of the metal-graphene complex, and only spatially separated Pb adatoms adsorbed on bridge and/or edge-plane sites can affect the vibrational properties of graphene. We expect that the lead adatoms can merge in large metallic clusters only at defect sites that reinforce the metal-graphene interactions. Our findings provide valuable insights into both heavy metal ion electrochemical analysis and metal electroplating on graphene interfaces that are important for designing effective detectors of toxic heavy metals.
在这里，我们报告了在碳化硅（Gr/SiC）上外延石墨烯上电化学沉积铅（Pb）作为模型金属。通过互补的电化学、物理和计算方法评估了电沉积的动力学和沉积物的形态特征。使用 Gr/SiC 作为电极可以跟踪与铅相关的氧化还原转化。对沉积过程中通过的电流瞬变的分析揭示了一种瞬时成核机制，该机制由局部随机分布在外延石墨烯上的核上的收敛质量传输控制。通过实验估计的表观扩散系数、拉曼光谱和扫描电子显微镜（SEM）研究证实了这种沉积物拓扑结构的关键观察结果。第一性原理计算表明，Pb 团簇在石墨烯表面的成核导致金属-石墨烯复合物的相互作用强度减弱，只有吸附在桥位和/或边缘位的空间分离的 Pb adatoms才能影响石墨烯的振动特性。我们预计，只有在强化金属-石墨烯相互作用的缺陷位置，铅 adatoms 才能合并成大的金属团簇。我们的研究结果为电化学分析重金属离子和在石墨烯界面上电沉积金属提供了有价值的见解，这对于设计有效的有毒重金属探测器非常重要。
