An electrochemically fabricated cobalt iron oxyhydroxide bifunctional electrode for an anion exchange membrane water electrolyzer.

For an anion exchange membrane water electrolyzer (AEMWE), exploring bifunctional electrodes with low cost and high efficiency is a crucial task for future renewable energy systems. Herein, we report a simple method to fabricate cobalt iron oxyhydroxide (Co z Fe 1- z O x H y ) bifunctional electrodes for AEMWEs. The bifunctional electrodes were prepared via one-pot electrodeposition on Ti paper (TP). By adjusting the electrodeposition conditions, the morphology and composition of Co z Fe 1- z O x H y /TP could be controlled. The Co 65 Fe 35 O x H y /TP electrode demonstrated the highest activity for overall water electrolysis owing to the maximized synergy effect between Co and Fe. The bifunctional activities of Co 65 Fe 35 O x H y /TP were well retained at -50 and 50 mA cm -2 for 12 h. Co 65 Fe 35 O x H y /TP, which shows the highest bifunctional activity, was employed in an AEMWE single cell as the anode and cathode. The AEMWE single cell employing Co 65 Fe 35 O x H y /TP showed a current density of 0.605 A cm -2 at a cell voltage of 2.0 V cell . The calculated energy efficiency of the single cell is 55.7% at 2.0 A cm -2 , which is comparable with those of the state-of-the-art AEMWE single cells with bifunctional electrodes. Furthermore, the cell voltage of the single cell with Co 65 Fe 35 O x H y /TP showed negligible degradation for 50 h at 0.6 A cm -2 .