Garrido Jose A, Nowy Stefan, Härtl Andreas, Stutzmann Martin
Walter Schottky Institut, Technische Universität München, Garching, Germany.
Langmuir. 2008 Apr 15;24(8):3897-904. doi: 10.1021/la703413y. Epub 2008 Mar 7.
We have investigated the electrochemical interface between diamond electrodes and aqueous electrolytes using electrochemical techniques such as cyclic voltammetry and ac impedance spectroscopy. High-quality CVD-grown boron-doped polycrystalline diamond electrodes and IIa single crystalline natural diamond electrodes have been used in this study. In the case of hydrogen-terminated diamond electrodes, the electrochemical interface is dominated by the electrochemical double layer. Frequency-dependent impedance spectroscopy reveals a potential regime in which the contribution of ion adsorption becomes relevant. We have conducted experiments to evaluate the effect of pH and ionic strength on the double layer. Our results suggest that only ions resulting from water auto-dissociation, i.e., hydroxide and hydronium ions, are responsible for ion adsorption and, thus, able to modify the charge at the double layer. In contrast, no effect of the adsorption of several dissolved ions (such as Na+, K+, Cl-) has been observed On the basis of the electrochemical characterization of H-terminated diamond surfaces, we also discuss the phenomenon of the surface conductivity in diamond, as well as the pH sensitivity of the diamond surface. The influence of the O2/OH- and H2/H3O+ redox couples on the origin of the surface conductivity is discussed.
我们使用循环伏安法和交流阻抗谱等电化学技术研究了金刚石电极与水性电解质之间的电化学界面。本研究中使用了高质量化学气相沉积生长的硼掺杂多晶金刚石电极和IIa型单晶天然金刚石电极。对于氢终止的金刚石电极，电化学界面由电化学双层主导。频率相关的阻抗谱揭示了一个离子吸附贡献变得显著的电位区域。我们进行了实验以评估pH值和离子强度对双层的影响。我们的结果表明，只有水自解离产生的离子，即氢氧根离子和水合氢离子，才负责离子吸附，从而能够改变双层电荷。相比之下，未观察到几种溶解离子（如Na+、K+、Cl-）吸附的影响。基于氢终止金刚石表面的电化学表征，我们还讨论了金刚石表面电导率现象以及金刚石表面的pH敏感性。讨论了O2/OH-和H2/H3O+氧化还原对表面电导率起源的影响。
