Adsorption and Oxidation Dynamics of Disperse Orange 3 on a Polycrystalline Pt Electrode Studied by in Situ Second Harmonic Generation
Adsorption and Oxidation Dynamics of Disperse Orange 3 on a Polycrystalline Pt Electrode Studied by in Situ Second Harmonic Generation
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原位二次谐波研究分散橙3在多晶Pt电极上的吸附和氧化动力学
DOI：
10.1021/acs.jpcc.0c07393
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发表时间：
2020
影响因子：
3.7
通讯作者：
Zhang Zhen
中科院分区：
文献类型：
--
作者：
Bai Ruipeng;Xue Man;Lin Yuan;Wen Rui;Guo Yuan;Zhang Zhen
分子水平上的吸附机理和电化学反应机理是电化学中的基本问题。本文采用原位二次谐波发生（SHG）结合原位紫外-可见光谱和电位阶跃技术研究了4-氨基-4 ′-硝基偶氮苯（分散橙子3，DO 3）分子在多晶Pt电极上的吸附和氧化动力学。在一定的电位阶跃下，不同偏振态组合下的时变SHG谱证实了DO 3分子中SHG强度的变化是由数密度变化引起的，而不是由取向角变化引起的.双电位阶跃实验和紫外-可见光谱证实了DO 3在界面上的吸附和氧化的协同作用导致了数密度的变化。在外加电位下，DO 3的吸附速率在前一百秒内大于电氧化速率，直到实现完全覆盖并达到最大SHG强度。随后，DO 3的氧化占主导地位，直到建立平衡，而SHG强度稳定。含时二次谐波谱表明，吸附过程和氧化反应的速率常数对电位有很强的依赖性。这项工作提供了深入的见解在电极/溶液界面的吸附和电化学反应。
Adsorption mechanisms and electrochemical reaction mechanisms at the molecular level are fundamental issues in electrochemistry. Here, we used in situ second harmonic generation (SHG) combined with in situ UV–vis spectra and potential step techniques to investigate the dynamics of the adsorption and oxidation of 4-amino-4′-nitroazobenzene (disperse orange 3, DO3) molecules on a polycrystalline Pt electrode. Time-dependent SHG spectra with different polarization combinations under certain potential steps confirmed that the SHG intensity change in the DO3 molecules resulted from the number density change rather than the orientation angle change. A double potential step experiment and UV–vis spectra verified that the number density change arose from the cooperative effects of adsorption and oxidation of DO3 at the interfaces. Under an applied potential, the adsorption rate of DO3 was greater than the electrooxidation rate in the first hundred seconds until full coverage was achieved and the maximum SHG intensity was reached. Subsequently, the oxidation of DO3 dominated until equilibrium was established, while the SHG intensity stabilized. In addition, the time-dependent SHG spectra showed that the rate constants of the adsorption process and the oxidation reaction were strongly dependent on the potential. This work provides in-depth insights into the adsorption and electrochemical reaction at electrode/solution interfaces.