Crystalline-amorphous heterointerfaces engineering through NiFe-OH integrated CoP core@shell 3-D arrays for high-efficiency simulated alkaline seawater splitting

In-situ design of crystalline-amorphous heterointerfaces in tandem can mitigate the problems of limited electrolyte diffusion, lower electrochemical active surface area (ECSA), and structural deformations, leading to higher efficiency for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Ascertaining these, we develop three-dimensional core@shell heterostructure by in-situ integrating ultrathin, amorphous NiFe-OH nanosheets onto crystalline CoP nanowire arrays on nickel foam (NF), forming a hierarchical CoP@NiFe-OH/NF bifunctional electrocatalyst for high-efficiency seawater splitting using 1 M KOH + 0.5 M NaCl as simulated alkaline seawater (SAS). The crystalline CoP core enhances electrical conductivity and lowers the hydrogen adsorption energy, suitable for HER. Meanwhile, the ultrathin and amorphous NiFe-OH nanosheet shell offers abundant unsaturated active sites, favorable electronic modulation, and facilitates electrolyte diffusion, leading to higher OER. Consequently, the crystalline-amorphous interfaces in CoP@NiFe-OH/NF induce electronic redistribution, enhance intrinsic activity, and facilitate rapid charge transfer, resulting in an outstanding HER and OER performance in SAS, requiring low overpotentials of only 87 and 230 mV at 10 mA cm −2 , respectively. When employed as both the anode and cathode, the CoP@NiFe-OH/NF (±) electrolyser achieves overall SAS splitting demanding low cell-potential of 1.54 V at 10 mA cm −2 , outperforming benchmark noble-metal-based catalysts and demonstrating long-term stability.