Heterogenizing MnO₂ nanostructure with industrial impurity ions for lead leakage-preventable anodes in zinc...

γ-MnO₂ precoated lead (Pb)-based anodes have shown high initial activity in heavy-metal pollution reduction and production improvement for zinc electrowinning in laboratory. However, the accumulated impurity ions (M) in industrial MnO₂-precursors restrict its industrial application. Herein, the heterostructure-induced rich oxygen-vacancies for M-MnO₂ and its higher activity (Pb/Co-MnO₂>Pb/Ni-MnO₂>Pb/Fe-MnO₂ ≈Pb/Cu-MnO₂>Pb/MnO₂) was reported. However, it reached a concentration threshold and afterwards provided the inhibited activity. Moreover, the Pb²⁺ diffusion-induced lead leakage is the dominant factor in the inactivation of anodes before extrinsic mechanical effects manifest, which follows: Pb/Fe-MnO₂>Pb/Cu-MnO₂>Pb/MnO₂ ≈Pb/Ni-MnO₂ ≈Pb/Co-MnO₂. Instead, due to the enhanced activity and suppressed lead leakage, Pb/Co-MnO₂ avoided about 12.4 % and 72.3 % lead-containing anode slime in comparison with Pb/MnO₂ and Pb/Fe-MnO₂ and minimized the contamination of zinc products by lead. Such complex effects also provide a cost-effective and environmental-friendly strategy for lead-leakage preventable Pb-based anodes in zinc electrowinning as it can reduce the exogenous dopants usage while still delivering competitive electrooxidation activity-stability.