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

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 (AB₂O₄ 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 CuCo₂O₄ possesses the most robust BIEF, which significantly accelerates the "electron relay" for H₂O₂ 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 CuCo₂O₄ system exhibits a bisphenol A degradation rate that is 2.45 and 5.69 times higher than those of CuFe₂O₄ and CuMn₂O₄ 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.