Synthesis Strategies, Catalytic Mechanisms and Multifunctional Applications of Heterojunction Nanozymes: A Review

Abstract Heterojunction nanozymes offer unique advantages, including interface charge regulation, multivalent-state cycling, defect engineering, and enhanced field responses. These merits overcome the bottlenecks of single-component nanozymes, such as low catalytic activity, poor stability, and limited functionality. They have shown great potential for applications in biomedical, environmental governance, and food detection fields. This article provides a systematic review of the latest research progress on heterojunction nanozymes. First, heterojunction nanozymes are classified by their diverse enzyme−mimetic activities (e.g., oxidase (OXD), catalase (CAT), peroxidase (POD)), followed by a systematic overview of their material components, key active centers, and representative synthetic strategies. We next discuss the charge-separation and directional-transfer mechanisms of type I, II, S, Z, and Schottky heterojunctions, and reveal how multivalent-state cycling, interface defects, external-field responses, and microenvironment activation regulate catalytic performance. Finally, we summarize their applications in biosensing, disease treatment, antibacterial therapy, pollutant degradation and detection, and food-contaminant analysis. We also discuss the remaining challenges and future directions, including interface precision design, mechanism elucidation, biosafety, and large-scale production. This article aims to provide comprehensive reference for the rational design and application expansion of high-performance multifunctional heterojunction nanozymes.