Examination of Water Electrolysis and Oxygen Reduction As Self-Discharge Mechanisms for Carbon-Based, Aqueous Electrolyte Electrochemical Capacitors

Water electrolysis and oxygen reduction as possible self-discharge mechanisms for carbon-based, aqueous H2SO4 electrolyte electrochemical capacitors is examined through a comparison of the predicted and actual effects of varying the dissolved oxygen an hydrogen content on self discharge. e. Water electrolysis, in the form of oxygen evolution, is no the self discharge mechanism on the positive electrode, although, the self-discharge profile is consistent with an activation-controlled Faradaic discharge or charge redistribution mechanism. The addition of hydrogen evidences no change in self-discharge from the negative electrode, and the profile is consistent with a diffusion-controlled mechanism, suggesting water electrolysis through hydrogen evolution is not the self discharge mechanism Oxygen reduction causes a large increase in self discharge on the negative electrode which necessitates purging the cell of oxygen. As such, water electrolysis is likely not the cause of self-discharge in carbon-based, aqueous electrolyte electrochemical capacitors but oxygen reduction is a cause of increased self-discharge on the negative electrode.