Full reaction mechanism of hydrogen peroxide catalyzed by reductive CoP nanoparticles: the enzyme-like activity

The hydrogen peroxide (H₂O₂) catalyzed by nanoparticles (NPs) demonstrates potential broad applications in the field of biomedicine and environmental protection. However, a systematic understanding of the catalytic mechanism severely limited the rational design of NPs with better enzyme-like activity and selectivity. Here, compared with the widely concerned Fe₃O₄ NPs, the decomposition process of H₂O₂ on reductive CoP NPs and pH-regulated peroxidase- and catalase-like activities with 3,3′,5,5′-tetramethylbenzidine (TMB) as reductive substrates were explored. All results show that OH· radical intermediates generated from the decomposition of H₂O₂*/OOH* at acidic conditions and complexed with TMB via H-bonds (complexed OH·) are the principal oxidant of TMB rather than free OH· as reported. Besides, the produced O*/OH* on CoP NPs shows negligible oxidation activity due to the strong reducibility of catalysts. The high coverage of O*/OH* from the dissociation of H₂O₂ (H₂O) at neutral (alkaline) pH conditions on CoP NPs enhances the dehydrogenation of H₂O₂ to O₂, leading to the transition between peroxidase- and catalase-like activities. [Figure not available: see fulltext.].