Oxygen‐Tolerant Hydrogen Peroxide Reduction Catalysts for Reliable Noninvasive Bioassays

: Noninvasive bioassays based on the principle of a hydrogen peroxide (H2 O2 ) cathodic reaction are highly desirable for low concentration analyte detection within biofluids since the reaction is immune to interference from oxidizable species. However, the inability to selectively reduce H2 O2 over O2 for commonly used stable catalysts (carbon or noble metals) is one of the key factors limiting their development and practical applications. Herein, catalysts that enable selective H2 O2 reduction in the presence of oxygen with fluctuating concentrations are reported. These catalysts consist of noble metal nanoparticles underneath an amorphous chromium oxide nanolayer, which inhibits O2 diffusion to the metal/oxide interface and suppresses its reduction reaction. Using these catalysts, analytes of low concentration in biofluids, including but not limited to glucose and lactate, are detected within the presence of various interferents. This work enables wide application of the cathodic detection principle and the development of reliable noninvasive bioassays.