Targeted design of metal defects in photocatalysts helps to realize stable and efficient wastewater treatment. Herein, a novel spinel Cu_1-xCo_2-yO_4-z with bimetal defects is precisely designed by a simple temperature programmed reduction method in hydrogen atmosphere. The co-existence of metallic defects leads to defects distortion forming polarization effect, which can significantly accelerate the separation of photogenerated carriers. By optimizing the band structure, Cu_1-xCo_2-yO_4-z induced in-situ H₂O₂ production (190 μmol L⁻¹·h⁻¹ with sacrificial agent and 78 μmol L⁻¹·h⁻¹ without sacrificial agent) to boost the generation of hydroxyl radical, and the photodegradation activity was 7.8 and 8.4 times for MB and Cr(VI) as that of CuCo₂O₄, respectively. Bimetal defects achieve high performance through in-situ production of H₂O₂ and purification of contaminants, providing novel strategies for the applications of spinel photocatalysts in environmental purification.