Unusual oxidase-mimetic catalytic performance surpassing peroxidase in amorphous CoOx: underlying mechanism and toward a novel H2O2-related detection paradigm†

Different from crystalline cobalt oxides (Co₃O₄ and CoO) and most reported nanozymes, amorphous CoO_x was found to exhibit better oxidase-like catalytic performance than the peroxidase one. Mechanistic investigations revealed that the introduction of H₂O₂ could decompose CoO_x into inactive Co²⁺ under acidic conditions, leading to the loss of catalytic activity. With the unusual phenomenon, a proof-of-concept “turn-off” cascade system was fabricated to detect glucose colorimetrically via combining CoO_x with glucose oxidase.