• • The Pt/FeCoNiMnCr HEH/NF electrocatalyst achieves an OER overpotential of 306 mV at 100 mA cm−2, surpassing commercial IrO2 (typically >320 mV at 10 mA cm−2) and enabling high-current-density operation essential for industrial electrolyzers.
• • For HER, the catalyst requires only 116 mV overpotential at 50 mA cm−2, comparable to Pt/C (≈30–50 mV at 10 mA cm−2) but with drastically reduced Pt loading due to atomic-level dispersion on the HEH matrix, addressing noble metal cost constraints.
• • In a two-electrode water splitting cell, the bifunctional catalyst delivers 20 mA cm−2 at a cell voltage of 1.56 V, which is among the lowest reported for Pt-based bifunctional catalysts, and maintains stable operation for over 50 h, indicating robust durability under continuous electrolysis.
• • The two-step electrodeposition at ambient temperature yields a three-dimensional porous structure with ultrathin nanosheets, providing a high electrochemically active surface area and efficient gas bubble release, which mitigates mass transport limitations at high current densities.