Interface engineering has emerged as a promising strategy for efficiently enhancing catalytic performance. Herein, we present a built-in electric field (BEF) strategy to assemble Co9S8/Ni3S2 heterojunctions confined in S-doped carbon matrix (SC) and anchored S-doped carbide wood framework (SCW). Leveraging BEF, Co-S-Ni charge transfer channels and the superior mass transfer properties inherent in wood’s unique structure, (Co9S8/Ni3S2)@SC/SCW exhibits a low overpotential of 220 mV at 50 mA cm−2, and remarkable stability. The experimental characterizations and theoretical simulation indicate that the constructed BEF can induce the directional transfer of electrons from Co9S8 to Ni3S2, which is beneficial for the adsorption of OH- owing to the electrostatic interaction, thereby promotes the formation of the highly active amorphous metal hydroxide oxides at lower OER potentials. This work provides a new perspective for exploring the design of energy storage and conversion catalysts based on renewable wood substrates.