Dynamic Redeposition Over Bidirectional Amorphous NiFe-Oxides toward Surface Self-Healing for the Alkaline Oxygen Evolution Reaction.

The NiFe-oxy/hydroxides (NiFeOH) have emerged as promising candidates for alkaline oxygen evolution reaction (OER) but suffer from irreversible metal dissolution to pose a great challenge to long-term stability. Here, a self-supported electrode of NiFeOH/FeNiO/SS-A (substrate-etched stainless steel, SS-A; interlayer-amorphous FeNiO oxide; catalytic layer-amorphous NiFeOH) is fabricated and presents rare self-healing property of surface cracks, as well excellent activity and stability. It is found that crack repair is driven by the redeposition of dissolved Fe and Ni ions from the amorphous interlayer involved in the OER process because no similar behavior is observed in Fe-free and crystalline interlayer-supported NiFeOH. Moreover, the repair performance is dependent on current density and electrolysis time, with 71% of surface cracks being repaired after 72 h operated on an industrial level of 500 mA cm. It needs to be emphasized that the irreversible dissolution of Fe and Ni from the catalytic layer of NiFeOH still occurs but is effectively suppressed. It is demonstrated that the construction of an amorphous FeNiO oxide interlayer in self-supported electrodes plays an important role in improving the stability and is expected to open up an opportunity for the design and develop highly efficient and durable alkaline OER catalytic electrodes.