Revealing Selectivity in Nanozyme Reactions via OH Adsorption: A Descriptor-Guided Mechanism for H ₂ O ₂ Activation on Doped Carbon Nanotubes

Controlling the catalytic selectivity of nanozymes remains a major challenge in redox nanomedicine. Although various carbon-based materials have been developed as enzyme-mimicking catalysts for H₂O₂ decomposition, doped carbon nanotubes (CNTs) remain underexplored, especially regarding their ability to direct peroxidase (POD) or catalase (CAT) pathways. Here, we conduct a systematic first-principles study of H₂O₂ activation on 70 single-walled CNTs with varying chiralities, diameters, and dopants (B, N, P, S). By calculating adsorption energies of key intermediates (H*, O*, OH*, OOH*), we establish strong linear correlations between Eads,OH and the reaction energies of different H₂O₂ decomposition pathways. We propose Eads,OH as a unified descriptor that predicts both activity and selectivity. N-doped CNTs favor OH* formation, while B- and N,P-co-doped CNTs promote O* intermediates─demonstrating two distinct POD-like mechanisms. This difference originates from dopant-dependent shifts in the p-band center, which tune adsorption strengths and reaction thermodynamics. Several doped CNTs, including B-doped CNT(5,5) and N,P-co-doped CNT(6,0), show strong POD selectivity, whereas pristine armchair CNTs prefer CAT-like behavior. Our work reveals how dopant and geometric modulation of CNTs govern catalytic selectivity at the molecular level. These insights not only clarify H₂O₂ reaction pathways on carbon nanozymes but also provide a descriptor-guided framework for designing selective and high-performance nanocatalysts.