D-band center coordination modulated enzyme-like activity in Fe-Cu dual-metal single-atom nanozymes

After explorations in a diversity of single-atom nanozymes (SAzymes), developing dual-centered SAzymes becomes a promising approach for superior catalytic performance. But confusing mechanisms including atomic coordination, spatial configuration, and metal–metal atom interaction hinder the development and design of SAzymes. Herein, a dual-centered Fe-Cu-N_x SAzyme exhibits excellent peroxidase (POD)- and catalase (CAT)-like activities with d-band center (ε_d) coordination of Fe and Cu in multiple reaction stages, which plays a critical role in the adsorption of H₂O₂ molecule and H₂O and O₂ release. Therefore, the d-band center coordination, which can be represented by ε_d(Fe)–ε_d(Cu) shifts, leads to the competition between one-side and bilateral adsorption, which determines the favorable reaction path with lower energy barriers. Based on experimental statistics, simulated formation energies, and reaction barriers, 3 configurations, Fe-Cu-N₆-I, Fe-Cu-N₈-II, and Fe-Cu-N₈-III, are modeled and validated. Impressively, configuration-dependent catalytic selectivity and the competition between one-side and bilateral adsorption can be unveiled by d-band center coordination paradigm analysis. Theoretical simulations suggest that the unsymmetrical charge distribution over the three Fe-Cu configurations could tune the adsorption strength compared with the counterparts FeN₄ and CuN₄. The present work provides a potential route for optimizing enzyme-like catalysis by designing the dual- or even triple-metal SAzymes, which demonstrates the large space to modulate the metal atomic configuration and interaction.