电解制备二氧化锰强酸性电解液中气体扩散电极的稳定性与失效行为

Stability and Failure Behavior of Gas Diffusion Electrodes in Strong Acid Media for Electrolytic Manganese Dioxide

采用气体扩散电极(GDE)代替传统析氢阴极电解制备二氧化锰(EMD),重点研究了气体扩散电极在强酸性MnSO4-H2SO4电解液中的稳定性、寿命及失效行为.结果表明:气体扩散电极在MnSO4-H2SO4电解液中重现性好、具有一定的稳定性,寿命可达400 h;平行实验表明,阳极沉积一定厚度的EMD是槽电压第一次升高的主要原因;电流密度为100 A m-2时,气体扩散电极失效前阴极过程的速度由氧的离子化反应和氧的扩散混合控制,失效后阴极过程由氧去极化和氢去极化共同组成,主要发生析氢反应;催化层聚四氟乙烯(PTFE)网络结构的破坏和镍网层的溶解是电极失效的原因之一;Pt的团聚降低了电极的电催化活性,是电极失效的主要原因;阴极失效是槽电压再次升高的主要原因.

Electrolytic manganese dioxide （EMD） was prepared using a gas diffusion electrode （GDE） instead of a traditional hydrogen evolution cathode. The stability, lifetime, and failure behavior of the GDE were studied in a strongly acidic MnSO4-H2SO, electrolysis system. The results show that the GDE has good reproducibility and stability, and its lifetime is up to 400 h in a MnSO4-H2SO4 electrolysis system. Parallel experiments indicate that the major reason for the first increase in the anode cell voltage is the deposition on the anode of a certain thickness of EMD. When the current density is 100 A. m-2, the cathode reaction rate is controlled by a mixture of oxygen ionization and oxygen diffusion before failure of the GDE, and the cathode reaction process consists of two simultaneous reactions after failure of the GDE, i.e., oxygen depolarization and hydrogen depolarization. Hydrogen depolarization is the main controlling process after GDE failure. One of the reasons for electrode failure is destruction of the polytetrafiuoroethylene （PTFE） network structure in the catalyst layer and dissolution of the nickel mesh layer. Platinum agglomeration reduces the electrocatalytic activity of the GDE, and this is the main reason for electrode failure. Cathode failure is the main reason for the second increase in the anode cell voltage.