Preparation and electrochemical properties of a novel porous Ti/Sn–Sb-RuOx/β-PbO2/MnO2 anode for zinc electrowinning

MnO2 coatings prepared in a sulfate system (S-MnO2) and MnO2 prepared in a nitrate system (N-MnO2) were successfully deposited on porous Ti/Sn-Sb-RuO x /β-PbO2 substrates by electrodeposition, and their electrochemical properties were studied in detail. The bath composition plays a very important role in the MnO2 coating prepared by electrodeposition at a low current density. The results of scanning electron microscopy show that a Ti/Sn-Sb-RuO x /β-PbO2/MnO2 electrode has a rough morphology and the unit cell is very good. At the same time, the surface cracks in the S-MnO2 coating are larger than those in the N-MnO2 coating. In addition, the N-MnO2 coating is composed of a fluffy sheet-like substance. The surface morphology of the N-MnO2 coating is denser than that of the S-MnO2 coating. The S-MnO2 coating consists of irregularly stacked granular particles. Further, the main crystal phase of MnO2 is γ type, and the main valence state of MnO2 is +4. The results show that the oxygen evolution potential of the N-MnO2 electrode is 63 mV lower than that of the S-MnO2 electrode, indicating that the N-MnO2 electrode has better oxygen evolution activity and electrochemical stability, which can also be confirmed by EIS test results. Under the accelerated life test conditions, the N-MnO2 electrode has a better service life of 77 h at a current density of 1 A cm-2 in 150 g L-1 H2SO4 and 2 g L-1 Cl- solution.