Lv Ze, Chen Zhen, Yu Qiang, Zhu Wei, You Hongjun, Chen Bangyao, Zheng Zhaoyi, Liu Yuanyuan, Hu Qi
Faculty of Science, Kunming University of Science and Technology Kunming 650093 China
RSC Adv. 2021 Aug 31;11(46):28949-28960. doi: 10.1039/d1ra04006e. eCollection 2021 Aug 23.
PbO-CoO-MnO electrodes, used in the electrowinning industry and in the degradation of organic pollutants, have demonstrated an elevated performance through macroscopic electrochemical measurements. However, few reports have investigated localized electrochemical performance, which plays an indispensable role in determining the essential reasons for the improvement of the modified material. In this study, the causes of the increase in electrochemical reactivity are unveiled from a micro perspective through scanning electrochemical microscopy (SECM), X-ray diffraction (XRD), Raman microscopy (Raman), and X-ray photoelectronic energy spectroscopy (XPS). The results show that the increase of electrochemical reactivity of the modified electrodes results from two factors: transformation of the microstructure and change in the intrinsic physicochemical properties. Constant-height scanning maps indicate that the electrochemical reactivity of the modified electrodes is higher than that of the PbO electrode on the whole and high-reactivity areas are orderly distributed, coinciding with the observations from SEM and XRD. Thus, one of the reasons for the improvement of the modified electrode performance is the refinement of the microscopic morphology. The other reason is the surge of the oxygen vacancy concentration on the surface of the coating, which is supported by XRD, Raman and XPS. This finding is detected by the probe approach curve (PAC), which can quantitatively characterize the electrochemical reactivity of a substrate. Heterogeneous charge transfer rate constants of the modified electrode are 4-5 times higher than that of the traditional PbO electrode. This research offers some insight into the electrochemical reactivity of modified PbO electrodes from a micro perspective.
用于电积工业和有机污染物降解的PbO-CoO-MnO电极，通过宏观电化学测量已展现出卓越的性能。然而，鲜有报告研究局部电化学性能，而局部电化学性能在确定改性材料性能提升的根本原因方面起着不可或缺的作用。在本研究中，通过扫描电化学显微镜（SECM）、X射线衍射（XRD）、拉曼显微镜（Raman）和X射线光电子能谱（XPS）从微观角度揭示了电化学活性增加的原因。结果表明，改性电极电化学活性的增加源于两个因素：微观结构的转变和内在物理化学性质的变化。等高线扫描图表明，改性电极的电化学活性总体上高于PbO电极，且高活性区域有序分布，这与扫描电子显微镜（SEM）和XRD的观察结果一致。因此，改性电极性能提升的原因之一是微观形态的细化。另一个原因是涂层表面氧空位浓度的激增，这得到了XRD、Raman和XPS的支持。这一发现通过探针逼近曲线（PAC）得以检测，该曲线可定量表征基底的电化学活性。改性电极异相电荷转移速率常数比传统PbO电极高4至5倍。本研究从微观角度为改性PbO电极的电化学活性提供了一些见解。
