Ultrathin Amorphous Nickel Doped Cobalt Phosphates with Highly Ordered Mesoporous Structures as Efficient Electrocatalyst for Oxygen Evolution Reaction

Herein, the facile preparation of ultrathin (≈3.8 nm in thickness) 2D cobalt phosphate (CoPi) nanoflakes through an oil-phase method is reported. The obtained nanoflakes are composed of highly ordered mesoporous (≈3.74 nm in diameter) structure and exhibit an amorphous nature. Attractively, when doped with nickel, such 2D mesoporous Ni-doped CoPi nanoflakes display decent electrocatalytic performances in terms of intrinsic activity, and low kinetic barrier toward the oxygen evolution reaction (OER). Particularly, the optimized 10 at% Ni-doped CoPi nanoflakes (denoted as Ni10-CoPi) deliver a low overpotential at 10 mA cm⁻² (320 mV), small Tafel slope (44.5 mV dec⁻¹), and high stability for OER in 1.0 m KOH solution, which is comparable to the state-of-the-art RuO₂ tested in the same condition (overpotential: 327 mV at 10 mA cm⁻², Tafel slope: 73.7 mV dec⁻¹). The robust framework coupled with good OER performance enables the 2D mesoporous Ni10-CoPi nanoflakes to be a promising material for energy conversion applications.