Constructing Flower‐Like Ni‐Doped Co ₃ O ₄ Nanozyme With Abundant Oxygen Vacancies for Enhanced Peroxidase Mimetic Catalysis

The construction of cobalt‐based nanozymes (e.g., “nanostructured Co 3 O 4 catalysts with enzyme‐mimicking activity”) with highly efficient peroxidase (POD)‐like activity remains a challenging task, due to the insufficient active sites and inefficient electron transfer. Herein, the flower‐like Ni‐doped Co 3 O 4 (Ni‐Co 3 O 4 ) nanozyme was synthesized by a two‐step method involving solvothermal and thermal treatment. The uniform doping of Ni improves the dispersibility and specific surface area of Co 3 O 4 nanoparticles, and induces the generation of more oxygen vacancies (O vac ) by regulating the surface Co 2+ /Co 3+ ratio. Compared with Co 3 O 4 , Ni‐Co 3 O 4 nanozyme shows much enhanced POD‐like activity in buffer (pH 5) and water under ambient temperature (25 ± 2°C). After repeated use for six times, Ni‐Co 3 O 4 retains more than 80% of the highest activity, proving the excellent reusability. Based on Ni‐Co 3 O 4 , practical colorimetric sensors were constructed for specific detection of H 2 O 2 and phenol. Ni doping effectively reduces the formation energy of O vac on the surface of Co 3 O 4 and enhances electron mobility for fast electron transport. The introduction of more O vac not only lowers the adsorption energy but also changes the dissociation pathway of H 2 O 2 on Co 3 O 4 nanozyme. This work provides a theoretical basis and experimental reference for the development and application of highly efficient nanozymes.