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CTAB對Pb?Ag陽極MnO2鍍膜電化學性能的影響

Effect of CTAB on the electrochemical performance of MnO2 coatings deposited on Pb?Ag anodes

  • 摘要: 工業鋅電積通常采用Pb–Ag合金(0.5%~1.0% Ag(質量分數))作為陽極材料,然而其催化析氧活性低,導致陽極析氧反應過電位高、電極表面Pb電化學腐蝕、能耗增加. 本文以十六烷基三甲基溴化銨 (CTAB) 為添加劑,通過干預Pb–Ag陽極表面MnO2的電結晶過程,誘導生成具有良好耐蝕性和析氧活性的MnO2膜層. 研究表明,鋅電積體系中適量CTAB的引入可加速Mn2+ → Mn3+中間體的氧化,促進MnO2的電結晶生長并均勻包覆在Pb–Ag基體上,有效提升電極的催化析氧活性和耐腐蝕性能. 在模擬長周期工業鋅電積過程中,1 g·L?1 CTAB輔助鍍膜下制得的Pb–Ag/MnO2陽極 (PAM-C1) 較之工業鍍膜條件下制備的MnO2鍍膜陽極 (IPAM),具有更優的析氧和耐蝕性能:500 A·m?2下,PAM-C1陽極的析氧電位 (2.09 V (vs RHE)) 較IPAM (2.14 V (vs RHE)) 低50 mV,且性能穩定;經15天電解,相較IPAM陽極,基于PAM-C1陽極的電鋅體系中溶鉛量由0.7 mg·L?1降低為0.6 mg·L?1.

     

    Abstract: In industrial zinc electrowinning processes, Pb–Ag alloys (typically containing 0.5%~1.0% Ag (mass fraction)) have been widely adopted as inert anodes due to their mechanical durability and cost-effectiveness. However, these anodes exhibit intrinsic limitations in strongly acidic sulfate electrolytes. The low catalytic activity of Pb–Ag alloys toward the oxygen evolution reaction (OER) leads to elevated anode potential and increased energy consumption during zinc production. This high overpotential not only raises power costs but also accelerates the electrochemical corrosion of the Pb–Ag anode. Specifically, lead on the surface undergoes oxidation, resulting in Pb dissolution into the electrolyte. These dissolved lead ions subsequently co-deposit on the cathode, contaminating the zinc product and reducing its purity. Furthermore, the uneven OER activity induces localized current density hotspots, exacerbating structural degradation and shortening anode service life. To address these issues, pre-coating Pb–Ag anodes with MnO2 has emerged as a promising solution. MnO2 coatings effectively enhance the corrosion resistance of Pb–Ag anodes and inhibit surface lead oxidation and dissolution. At the same time, the MnO2 film serves as an excellent catalytic layer, significantly improving the oxygen evolution performance of the electrode. However, the MnO2 film prepared via traditional coating processes often suffer from a loose structure, poor adhesion, and limited protective effects on the Pb–Ag substrate. In the electrodeposition process, additives play a crucial role in optimizing deposit quality, adhesion, and performance while ensuring efficient and consistent electroplating results. Inspired by this, the incorporation of additives is anticipated to improve MnO2 film quality on Pb–Ag anodes. In this study, cetyltrimethyl ammonium bromide (CTAB) was used as an additive to induce the formation of MnO2 films with enhanced corrosion resistance and OER activity by modulating the electrocrystallization process on the Pb?Ag surface. The results demonstrate that introducing appropriate amounts of CTAB into the zinc electrodeposition system accelerates the oxidation of Mn2+ to Mn3+ intermediates, promotes uniform electrocrystallization of MnO2 on the substrate, and significantly enhances both catalytic activity and corrosion resistance of the electrode. Comparative tests between CTAB-modified anodes (PAM-C) and conventionally coated MnO2 anodes (IPAM) revealed substantial performance improvements. During long-term simulated zinc electrowinning, the CTAB-assisted Pb-Ag/MnO2 anode prepared with 1 g·L?1 (PAM-C1) showed superior OER performance and corrosion resistance compared to IPAM. At 500 A·m?2, the oxygen evolution potential of PAM-C1 (2.09 V (vs RHE)) was 50 mV lower than that of IPAM (2.14 V (vs RHE)), while maintaining stable performance. After 15 days of electrolysis, the lead concentration in the PAM-C1-based system decreased from 0.70 mg·L?1 to 0.61 mg·L?1 compared to the IPAM system. The enhanced performance of the PAM-C1 anode could contribute to more efficient and environmentally friendly zinc production. This work presents a promising approach to reducing energy consumption and improving product quality through additive-regulated MnO2 coating of Pb–Ag anodes, offering valuable insights for the sustainable development of the zinc electrowinning industry.

     

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