It remains challenging to develop economical and bifunctional electrocatalysts toward oxygen/hydrogen evolution reactions (OER/HER). Herein, we construct Co₉S₈ nanoflakes decorated Co₃O₄ nanoarrays with enriched heterogeneous interface zones on Ni foam (Co₉S₈@Co₃O₄/NF) via a novel step-wise approach. The Co₉S₈@Co₃O₄/NF hybrid manifests excellent performance with low overpotentials of 130 mV for HER (10 mA·cm^–2) and 331 mV for OER (100 mA·cm^–2), delivering a small voltage of 1.52 V for water splitting at 10 mA·cm^–2 as well as outstanding catalytic durability, which surpasses precious metals and previously reported earth-abundant nanocatalysts. Further experimental and theoretical investigations demonstrate that the excellent performance is attributed to the followings: (ⅰ) Highly conductive Ni facilitates the efficient charge transfer; (ⅱ) porous core-shell nanoarchitecture benefits the infiltration and transportation of gases/ions; (ⅲ) heterogeneous interface zones synergistically lower the chemisorption energy of hydrogen/oxygen intermediates. This work will shed light on the controllable synthesis and engineering of heterostructure nanomaterials for clean energy storage and conversion technologies.