Operando Cooperated Catalytic Mechanism of Atomically Dispersed Cu−N₄ and Zn−N₄ for Promoting Oxygen Reduction Reaction

Abstract

Dual-metal single-atom catalysts exhibit superior performance for oxygen reduction reaction (ORR), however, the synergistic catalytic mechanism is not deeply understood. Herein, we report a dual-metal single-atom catalyst consisted of Cu-N₄ and Zn-N₄ on the N-doped carbon support (Cu/Zn-NC). It exhibits high-efficiency ORR activity with an E_onset of 0.98 V and an E_1/2 of 0.83 V, excellent stability (no degradation after 10 000 cycles), surpassing state-of-the-art Pt/C and great mass of Pt-free single atom catalysts. Operando XANES demonstrates that the Cu-N₄ as active center experiences the change from atomic dispersion to cluster with the cooperation of Zn-N₄ during ORR process, and then turns to single atom state again after reaction. DFT calculation further indicates that the adjustment effect of Zn on the d-orbital electron distribution of Cu could benefit to the stretch and cleavage of O-O on Cu active center, speeding up the process of rate determining step of OOH*.