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.