Preparation and electrochemical properties of a novel porous Ti/Sn–Sb-RuO(x)/β-PbO(2)/MnO(2) anode for zinc electrowinning

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