“The Ce electrolyte is highly oxidative, which poses a challenge towards the stability of anion membrane,” Daoud said. “Thus, the stability and selectivity of anion membrane require further improvement.”

The device achieved a voltage plateau of 2.3 V at 20 mA cm − 2, energy efficiency of 71.3% at 60 mA cm − 2, and a record average Coulombic efficiency of 94% during cycling.