До теорії імпедансу дифузійно-контрольованої адсорбції нейтральних молекул з дифузійного шару Нернста на шерехатому електроді

• Datum: 2025
• 1. Verfasser: Gichan, О.І.
• Format: Artikel
• Sprache: Englisch
• Veröffentlicht: Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2025
• Schlagworte: імпеданс; подвійний шар; адсорбція; ємність; дифузія; шерехатий електрод; дифузійний шар Нернста
• Online Zugang: https://www.cpts.com.ua/index.php/cpts/article/view/822
• Назва журналу: Chemistry, Physics and Technology of Surface

The influence of a weak harmonic roughness of electrode surface, and the near-electrode layer thickness on the frequency characteristics of constituents of the adsorption impedance for a step of diffusion-controlled adsorption of neutral molecules from the Nernst diffusion layer has been analyzed. It has been done based on the expression for the generalized finite adsorption impedance for an electrode with a model harmonic roughness describing by a perturbation parameter equals to the ratio of the amplitude of the surface oscillations to its period. It allows us to separate the contributions of the double layer and adsorption capacitances to the adsorption impedance. It has been shown that the peculiarities of adsorption from a thin layer on a rough electrode can be observed at low frequencies. At high frequencies, the characteristic functional dependences on frequency coincide with those for a semi-infinite layer. The roughness of the interface raises its capacitance. At high frequencies, the capacitance increase on a rough electrode is determined by a geometric roughness factor. At low frequencies, this capacitance depends on the adsorption conditions. The additional adsorption capacitance is determined by the mass transport of surface-active species to the electrode with a model roughness. The electrode roughness raises the absolute value of the interfacial capacitance. Depending on perturbation parameter, relaxation time of diffusion-controlled process, and the Nernst diffusion layer thickness, a second loop can appear in a complex frequency dependence of interfacial capacitance. The high-frequency loop is caused by the charge and discharge of the double layer, while the low-frequency loop characterizes transport processes in the near-electrode layer. The electrode roughness changes the distribution of relaxation times and the phase angle of the adsorption impedance. At low frequencies, the phase angle depends also on the Nernst diffusion layer thickness. The dependence of the roughness function obtained in the case of a weak harmonic surface roughness on the system’s parameters has been analyzed. It has been shown that the roughness function decreases as the perturbation parameter decreases.