The efficiency of energy storage technologies such as water splitting and metal-air batteries is limited by the sluggish dynamics of the oxygen evolution reaction (OER). Herein, we report a galvanic replacement-mediated method for in-situ growth of iron-nickel nitride on carbon nanotubes (CNTs) as a powdery catalyst for OER. This in-situ grown structure creates intimate interaction between the active substance of Fe2Ni2N and CNTs so as to accelerate charge transfer in the catalytical interface. First-principles calculations reveal that the Fe2Ni2N is intrinsically metallic, and the contribution mainly derives from the Fe atoms at corner sites of crystal structures. A good synergistic effect between metallic Fe2Ni2N with excellent intrinsic activity and conductive CNTs lead to outstanding electrochemical performance with a low overpotential (η 10 mAcm-2 = 282 mV) and Tafel slope (38 mV dec−1), as well as good long-term stability.