Bipolar membranes (BPMs) are being studied for applications in fuel cells, water and CO₂ electrolysis, and pH swing devices for ocean capture of CO₂. In redox flow batteries, a BPM can manage proton balance between acidic and basic electrolytes, effectively adding up to 800 mV to the cell voltage. Functionalizing graphitic electrodes by diazonium chemistry (Fig. 1) addresses the problem of their slow electron transfer kinetics in alkaline media. This strategy is being applied to carbon electrodes for various electrochemical energy conversion applications.

Alkaline electrochemical systems such as fuel cells, electrolyzers, redox flow batteries, and metal-air batteries offer an interesting alternative to acidic polymer membrane electrolyte (PEM) systems because they do not require precious metal electrocatalysts. We have studied layered double hydroxides as solid-state hydroxide ion (OH^-) conductors for these devices and recently discovered that Ag₂O also conducts OH^- ions through the oxidative doping mechanism shown in Fig. 2. Ag₂O is a promising alternative to polymeric ionomers in alkaline fuel cells because it is resistant to degradation by oxygen radical species.