An Electron Relay Driven by Built‐in Electric Fields for Self‐Sustaining and External‐Energy‐Free Fenton‐Like Catalysis

Efficiency in Fenton‐like processes is often bottlenecked by the sluggish redox cycling of metal centers. Herein, we report a self‐sustaining and energy‐free catalysis strategy by constructing an intermetallic potential difference‐induced built‐in electric field (BIEF) to drive an “electron relay” within bimetallic spinels (AB 2 O 4 A = Ni, Cu, Zn; B = Co, Fe, Mn). The intrinsic potential gradient between the A‐site and B‐site metals triggers a spontaneous charge redistribution, establishing an atomic‐level electron transmission channel. Experimental results and theoretical calculations reveal that CuCo 2 O 4 possesses the most robust BIEF, which significantly accelerates the “electron relay” for H 2 O 2 activation. This mechanism enables a closed‐loop valence cycling between (Cu(II)/Cu(I) and Co(III)/Co(II)), achieving highly efficient and continuous generation of reactive oxygen species without any external energy input. Consequently, the CuCo 2 O 4 system exhibits a bisphenol A degradation rate that is 2.45 and 5.69 times higher than those of CuFe 2 O 4 and CuMn 2 O 4 respectively, along with exceptional stability across a wide pH range (5–9). When integrated into a hollow fiber membrane, the system demonstrates a high flux of 318 L·m −2 ·h −1 and long‐term operational durability. This work provides a transformative perspective on designing autonomous catalytic systems for sustainable water remediation.