• • Bacterial/Fe3O4 hybrid materials achieved significantly higher gallic acid degradation rates than Fe3O4 alone, with hydroxyl radicals showing the highest correlation (r = 0.98) to the degradation rate constant, confirming their dominant role in the oxidative pathway.
• • Electroactive bacteria promote the formation of oxygen vacancies (OVs) on Fe3O4 surfaces, which are positively correlated with ROS generation, thereby accelerating electron transfer and enhancing catalytic efficiency.
• • The optimal temperature range for gallic acid degradation was 30–40 °C, attributed to bacterial temperature sensitivity, indicating a trade-off between bacterial activity and catalytic performance.
• • The hybrid system generates multiple ROS species (hydroxyl radicals, superoxide radicals, and singlet oxygen), with hydroxyl radicals identified as the primary species responsible for degradation, as verified by quenching experiments.