Same Nanozyme, Different Rankings: A Critical Assessment and a Practical Reference Standard for Peroxidase-Mimicking Nanozymes

Abstract Nanozymes are widely investigated as stable and cost-effective alternatives to natural enzymes, yet their quantitative evaluation remains hindered by the lack of standardized metrics for catalytic activity. This limitation leads to inconsistent comparisons across studies and impedes the assessment of structure–activity relationships. Here, we demonstrate that using the same experimental data set, different normalization strategies yield turnover numbers that vary by up to 5 orders of magnitude. This finding underscores the urgent need for a unified, physically consistent approach to enable meaningful cross-study benchmarking of nanozymes and enzymes. Using bimetallic Au@Pt core–shell and trimetallic Au@Ag–Pt nanozymes with surface-distributed Pt as model systems, we experimentally validate two normalization strategies (per particle and per surface-accessible atom), which are relevant to bioanalytical and materials-design applications, respectively. Furthermore, we propose a simple and reproducible reference standard for peroxidase activity based on Cu2+-mediated TMB oxidation. Collectively, these results clarify how normalization strategy should be matched to the intended application and provide practical tools for more consistent catalytic reporting.