We demonstrated that the electronic-band structure holds the key to electrocatalytic durability towards the oxygen-evolution reaction (OER). Density functional theory (DFT) revealed the characteristic of Ni–Ni bonding interactions within Ni₅P₄, Ni₅P₂ and Ni₃P were different and could influence their phase stabilities during the OER. Ni₅P₂ and Ni₃P exhibited very robust OER performances at high current density (>350 mA cm⁻²) over 12 h whereas, for Ni₅P₄, obvious deterioration was observed. In situ/ex situ X-ray near-edge structure, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy indicated the phase stability of Ni₅P₄, Ni₅P₂ and Ni₃P behaved differently during the OER. These materials transformed to Ni oxyhydroxide but the process for Ni₅P₂ and Ni₃P was much slower even under high anodic potential 1.6 V (V vs. RHE). These results supported the theoretical prediction and provide a refreshing viewpoint for designing reliable electrocatalysts for the OER.