Engineering multi-shell Mn-Co oxide for ultrasensitive electroanalysis of Pb(II) in mining subsidence area water with promotion of adsorption and electron mediation: Behaviors and mechanisms of Mn(II)/Mn(III) and Co(II)/Co(III) cycles

• Published in: Electrochimica acta 2020-11, Vol.360, p.136991, Article 136991
• Main Authors: Li, Shan-Shan, Cheng, Xing-Liang, Xu, Qian-Qian, Zhou, Wen-Yi, Zhang, Yongxing, Yang, Meng
• Format: Article
• Language: English
• Subjects: Adsorption; Electrochemical analysis; Electrochemical sensing; Electrolytic analysis; Electron mediation; Grippers; HMIs; Lead; Mediation; Metal oxides; Multi-shell Mn-Co oxide; Nanomaterials; Photoelectrons; Subsidence; Surface chemistry; Surface cycle; Transition metal oxides; X ray photoelectron spectroscopy
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2020.136991

•Mn-Co oxide multi-shell hiberarchy microsphere was fabricated as sensing interface.•Hypersensitive detection of Pb(II) was achieved with sensitivity of 120.72 µA µM−1.•Mn, Co and O exposed on surface are active sites for redox reaction and adsorption.•The variable valence mediation effect highly improves the sensing behavior.•The electrode has impressive performance for the water of mining subsidence area. It still remains unclear that the intrinsic structure-sensing property interplay of diverse transition metal oxides based sensing materials, although they have been applied in the field of environmental analysis and have achieved great progress. In this work, we performed X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and in situ electrochemical experiment to investigate the structure-sensing interplay of Mn-Co oxide (MnCo2O4) multi-shell hiberarchy microsphere. The comprehensive studies conclusively show that the active sites on MnCo2O4 surface work as key role in determining the electrochemical behavior through the aspect of adsorption and electrocatalytic activity. In detail, the exposed oxygen on the surface of MnCo2O4 forming amounts of –OH can act as grippers to adsorb the Pb(II) in water, and then the adsorbed Pb(II) can directly occur redox in situ by the mediation of Mn(II)/(III) and Co(II)/(III) cycle on the exposed Mn and Co active sites. As a result, an excellent electroanalytical behavior (sensitivity of 120.72 µA µM−1) toward Pb(II) could be effectively improved on MnCo2O4. The fabricated electrode also showed impressive electroanalytical performance for Pb(II) in mining subsidence area. Our findings will provide new insights and effective directions for designing ultr-sensitive nanomaterials based on variable valence mediation engineering in tuning the activity of transition metal oxides. [Display omitted]