Iron-doped nickel sulfide @ phosphate heterostructures nanosheets constructed by solvothermal P2S5 and layered double hydroxides for electrocatalytic oxygen evolution

The design of efficient and active electrocatalysts for oxygen evolution reaction (OER) is crucial for renewable energy generation. Here, crystalline iron-doped nickel sulfide core, amorphous iron-doped nickel phosphate shell heterostructured nanosheets grown on nickel foam (Ni0.9Fe0.1S@NiFe(PO4)x/NF) are prepared by solvothermal reaction of nickel iron layered double hydroxides on NF (NiFe-LDH/NF) with P2S5. The heterogeneous interface induces the electronic interaction between the Ni0.9Fe0.1S and NiFe(PO4)x phases, that is beneficial for OER. The electrode exhibits excellent OER performance, requiring only a low overpotential of 208 mV and 246 mV at current densities of 10 mA cm−2 and 100 mA cm−2, respectively, and a low Tafel slope of 38.75 mV dec−1 in 1 M KOH. The OER mechanistic pathways of Ni0.9Fe0.1S@NiFe(PO4)x/NF and NiFe-LDH/NF both involve decoupled electron and proton transfer processes, and the contribution of lattice oxygen oxidation mechanism (LOM) is higher for Ni0.9Fe0.1S@NiFe(PO4)x/NF. The increase in the acidity of Ni sites leads to the enhanced participation of LOM for Ni0.9Fe0.1S@NiFe(PO4)x/NF. Additionally, the electrode also shows high long-term durability (150 h), with the transition of surface metal sulfides and phosphates to hydroxide and (oxy) hydroxide observed. This study provides a new idea for the development and design of heterogeneous oxygen evolution electrocatalytic materials.