锌电积用Pb-Ag阳极MnO_(2)镀膜的电化学性能

Electrochemical performance of MnO_(2) films coated on Pb-Ag anode for zinc electrowinning

锌电积用Pb-Ag阳极存在析氧过电位高、表面铅易电化学氧化溶解,造成阴极电锌品质低等突出问题,如何减少阳极的溶铅污染并提升其催化析氧活性、降低反应能耗,成为亟待解决的难题。本文在Pb-Ag阳极表面电沉积一层均匀、致密的MnO_(2)薄膜,采用SEM、XRD和ICP等对MnO_(2)催化层的表面微观形貌、晶体结构和溶液含铅量进行分析;采用CV、LSV、EIS和Tafel等对Pb-Ag/MnO_(2)阳极的析氧催化活性和耐腐蚀性能进行分析。结果表明:在MnSO_(4)-H_(2)SO_(4)溶液中,当循环速率为200 mL/min、温度为80℃时,以4 mA/cm^(2)电沉积120 min制备的Pb-Ag/MnO_(2)镀膜电极具有最佳的催化析氧和耐蚀性能;PbAg阳极经优化镀膜后,50 mA/cm^(2)时其析氧过电位由936 mV降低为648 mV,腐蚀电流密度由7.03μA/cm^(2)降低至0.66μA/cm^(2);相较于Pb-Ag阳极,基于Pb-Ag/MnO_(2)阳极的15 d长周期电锌体系中溶铅量由0.61 mg/L降至0.29 mg/L。

The Pb-Ag anode utilized in zinc electrowinning exhibits a high overpotential for oxygen evolution,leading to the facile dissolution of surface lead through electrochemical oxidation,thereby producing low-quality cathode zinc.To address this issue and mitigate lead pollution caused by anode dissolution of the Pb-Ag anode,enhancing its catalytic activity for oxygen evolution and reducing energy consumption during the electrowinning process is imperative.In this study,a uniform and compact MnO_(2) films electrodeposited onto the Pb-Ag anode surface.The morphology,crystal structure and solution lead content of the MnO_(2) catalytic layer were thoroughly characterized using SEM,XRD,and ICP techniques,respectively.Furthermore,the oxygen evolution catalytic activity and corrosion resistance of the Pb-Ag/MnO_(2) anode were evaluated by CV,LSV,EIS and Tafel electrochemical tests.The results show that,under optimal electrodeposition conditions(4 mA/cm^(2) for 120 min in MnSO_(4)-H2SO_(4) electrolyte at temperature of 80℃and solution circulation rate of 200 mL/min),the Pb-Ag/MnO_(2) electrode exhibits superior performance in terms of both catalytic oxygen evolution and corrosion resistance.Specifically,after coating the Pb-Ag anode with MnO_(2) film under these optimized conditions,the oxygen evolution overpotential at 50 mA/cm^(2) decreases from 936 mV to 648 mV while simultaneously reducing corrosion current density from 7.03μA/cm^(2) to 0.66μA/cm^(2).Compared with the Pb-Ag anode,the dissolved lead content in the solution decreases significantly from 0.61 mg/L to only 0.29 mg/L after continuous long-term zinc electrowinning experiments lasting 15 d based on the Pb-Ag/MnO_(2) anode.