Hydroxide ion conduction in Ni–Al layered double hydroxide

Ionic conductivities of Ni/Al layered double hydroxides (Ni–Al LDHs) intercalated with CO32-, Cl− and OH− were evaluated in the temperature range of 25–80 °C under 65–95% relative humidity. X-ray diffraction and Fourier transform infrared measurements confirmed the formation of Ni–Al LDHs intercalated with CO32-, Cl− and OH−. In the AC conductivity measurements, Ni–Al LDH intercalated with CO32- (Ni–Al CO32- LDH) showed the highest ionic conductivity among them. The ionic conductivity of Ni–Al CO32- LDH was 1.3 × 10−2 S cm−1 at 80 °C under 80% relative humidity. The electromotive force for the water vapor concentration cell using Ni–Al CO32- LDH showed similar behavior with that using anion exchange membrane, indicating that Ni–Al CO32- LDH is a hydroxide ion conductor. Pelletized Ni–Al CO32- LDH was confirmed to work as the electrolyte of alkaline-type direct ethanol fuel cell.

► Ni–Al LDH intercalated with CO32- is found to show quite high “hydroxide ion conducting” property. ► Interlayer anions have effect on ionic conductivities of Ni–Al LDHs. ► Ni–Al LDH intercalated with CO32- is the highest ionic conductivity. ► The ionic conducting species of Ni–Al CO32- LDH is confirmed to be hydroxide ion.