Room Temperature Synthesis of Gradient-Distributed Ni/Fe Sites in Layered Double Hydroxides for Enhanced Oxygen Evolution Reaction.

NiFe-based materials, especially NiFe layered double hydroxides (LDHs), are recognized as the most promising non-precious metal electrocatalysts for alkaline oxygen evolution reaction (OER). However, the precisely designed distribution of active sites for enhancing activities is still significantly restricted due to the lack of reasonable modulation strategies. Herein, sulfur doped Ni/Fe gradient-distributed LDH (GD-NiFe LDH/S) is fabricated by facile air-induced strategy at room temperature. This strategy accelerates the growth process with abundant CO and O in air, which promotes the inward migration of Fe species, resulting in gradient distribution with Ni/Fe-rich edge/planar. This allows significant enhancement of Ni/Fe synergistic effect, which plays a vital role in OER. Moreover, the sharp pine-like morphology of GD-NiFe LDH/S endows superhydrophilicity/aerophobicity characteristics, facilitating electrolyte penetrating and oxygen releasing. The optimized GD-NiFe LDH/S delivers superior OER performance with low overpotentials of 234 and 270 mV at 10 and 100 mA cm. The assembled anion exchange membrane water electrolyzer only requires 1.90 V at 1.0 A cm and 2.10 V at 1.5 A cm with robust stability for at least 130 h. This work introduces a facile air-induced strategy under room temperature to controllably design active site distributions of LDH for enhanced OER performance.