Construction of hierarchical FeP/Ni₂P hollow nanospindles for efficient oxygen evolution

In this work, we demonstrate the design and construction of hierarchical FeP/Ni₂P hybrid hollow nanospindles (HNSs) as an active and stable electrocatalyst for the oxygen evolution reaction (OER). Employing solid FeOOH NSs coated with a thin layer of SiO₂ as the template and Ni(NO₃)₂·6H₂O as the reagent, 2D nickel silicate (Ni₃Si₄O₁₀(OH)₂·5H₂O) nanosheets were grown on the surface of the FeOOH spindles through a facile solvothermal method to produce hierarchical FeOOH@Ni₃Si₄O₁₀(OH)₂·5H₂O hybrid NSs. Following a subsequent phosphorization treatment, the as-prepared solid composite NSs were successfully converted into FeP/Ni₂P HNSs. The SiO₂ nanocoating was found to play a crucial role in this synthesis, and served not only as a reagent for the solvothermal reaction, but also as a nanoreactor for preserving the template morphology after the phosphorization treatment. Benefiting from the unique hollow and hierarchical nanoscaled hybrid structure, the FeP/Ni₂P HNS electrocatalyst displays superior electrocatalytic activity for the OER to Fe_xP, Ni₂P and the physical mixture of Fe_xP and Ni₂P samples, achieving an overpotential of 234 mV at a current density of 10 mA cm^-2 in 1 M KOH and a relatively low Tafel slope of 56 mV dec^-1.