Robust CoP@NiFe LDH/Ni heterostructured electrodes for efficient overall water splitting with high current density

Alkaline water electrolysis techniques have enormous potential for industrial-scale hydrogen generation, but a lack of effective and low-cost bifunctional electrocatalysts capable of steady high-current density operation has hampered progress. Layered double hydroxides (LDHs) have been considered promising OER electrocatalysts, but their poor electrical conductivity impedes hydrogen evolution reaction (HER) activity. Integrating LDHs with transition metal phosphides (TMPs) can potentially achieve bifunctional capability by overcoming individual limitations. Herein, CoP@NiFe LDH/Ni heterostructured catalyst was rapidly synthesized by a scalable two-step electrodeposition method. The integration of NiFe LDH with CoP enhanced its electrical conductivity. Meanwhile, electron transfer occurred from the metal atoms to the more electronegative phosphorus, facilitating phosphorus to act as a proton acceptor and expedite the HER process. Benefiting from the synergistic integration and optimized electronic structure, CoP@NiFe LDH/Ni exhibited excellent alkaline water-splitting performances with low overpotentials of 260 mV for HER and 351 mV for OER at 400 mA/cm2. The CoP@NiFe LDH/Ni twoelectrode-based alkaline electrolyzer displayed a cell voltage of 2.13 V and stable operation for 100 h at a high current density of 1000 mA/cm2. This work elucidates a strategy to tackle critical challenges impeding the design and preparation of high-current-density tolerant bifunctional electrocatalysts.