Ultrasmall NiFe layered double hydroxide strongly coupled on atomically dispersed FeCo-NC nanoflowers as efficient bifunctional catalyst for rechargeable Zn-air battery - Carbon4Energy

Atomically dispersed FeCo-NC material with 3D flower-like morphology was investigated as unique substrate for the controllable deposition of ultrasmall NiFe layered double hydroxide nanodots (termed as NiFe-ND) to simultaneously promote the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The size-limiting growth of NiFe-ND (~4.0 nm in diameter) was realized via the confinement of the 3D flower-like mesoporous structure and the rich N/O functionality of FeCo-NC. Benefiting from the distinctive structure with the simultaneous maximum exposure of both OER and ORR active sites, the NiFe-ND/FeCo-NC composite showed a 0.85 V ORR half-wave potential and a 1.66 V OER potential in 0.1 M KOH at 10.0 mA cm-2. In-situ Raman analysis suggested the origin of OER activity to be the Ni sites on NiFe-ND/FeCo-NC. Moreover, the NiFe-ND/FeCo-NC-assembled Zn-air batteries (ZAB) exhibited a very small discharge-charge voltage gap of 0.87 V at 20 mA cm-2 and robust cycling stability. Furthermore, the NiFe-ND/FeCo-NC composite was also applicable for fabricating all-solid-state ZAB to power wearable electronics and rendered superior cycling stability under deformation. Our work may enlighten the new applicable branch of atomically dispersed metal-nitrogen-carbon materials as unique substrate for fabricating multifunctional electrocatalysts.