Meng Hui-min

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

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- H2 SO4 electrolysis system. The results show that the GDE has good reproducibility and stability, and its lifetime is up to 400 h in a MnSO4- H2 SO4 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 polytetrafluoroethylene(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.