Moderate d-band center determines the high activity of Cu₂O laccase nanozymes

Designing high-performance laccase-mimicking nanozymes could realize effective oxidation of phenolic pollutants, while solve the unstable problem of natural laccase. Cu₂O has same Cu active center with natural laccase, but its catalytic activity is not satisfactory. In this work, by simply regulating the exposed facet of Cu₂O, we found that its catalytic activity could be greatly improved. Cubic Cu₂O (c-Cu₂O) with single exposed (100) facet exhibited the highest activity, followed by short hexapods (111), while rhombic dodecahedrons (110) showed the poorest performance. The activity of c-Cu₂O was 2.5 times higher than that of natural laccase and exceeded most of other copper-based laccase mimics. c-Cu₂O also exhibited superior stability and universal catalytic activity toward several phenolic compounds. Theoretical calculations demonstrate that the d-band center of (100) facet is moderate (-1.74 eV) compared with (110) (-1.71 eV) and (111) (-1.86 eV), which enables balanced substrate adsorption and optimal oxygen activation, thereby resulting in the highest catalytic activity. This study provided a simple approach for realizing highly-effective laccase-like activity and elucidates the atomic mechanism of facet-dependent activity of Cu₂O, which provides fundamental insights for designing high-performance nanozymes.