No 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 ad ual-metal single-atom catalyst consisted of Cu À N 4 and Zn À N 4 on the N-doped carbon support (Cu/Zn À NC). It exhibits high-efficiency ORR activity with an E onset of 0.98 Vand 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.O perando XANES demonstrates that the CuÀN 4 as active center experiences the change from atomic dispersion to cluster with the cooperation of Zn À N 4 during ORR process,a nd 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,s peeding up the process of rate determining step of OOH*.

NiFe-layered double hydroxides (NiFe-LDH) are among the most active catalysts developed to date for the oxygen evolution reaction (OER) in alkaline media, though their long-term OER stability remains unsatisfactory.H erein, we reveal that the stability degradation of NiFe-LDH catalysts during alkaline OER results from adecreased number of active sites and undesirable phase segregation to form NiOOH and FeOOH, with metal dissolution underpinning both of these deactivation mechanisms.F urther,w ed emonstrate that the introduction of cation-vacancies in the basal plane of NiFe LDH is an effective approach for achieving both high catalyst activity and stability during OER. The strengthened binding energy between the metals and oxygen in the LDH sheets, together with reduced lattice distortions,b oth realized by the rational introduction of cation vacancies,d rastically mitigate metal dissolution from NiFe-LDH under high oxidation potentials,r esulting in the improved long-term OER stability. In addition, the cation vacancies (especially M 3+ vacancies) accelerate the evolution of surface g-(NiFe)OOH phases, therebyboosting the OER activity.The present study highlights that tailoring atomic cation-vacancies is an important strategy for the development of active and stable OER electrocatalysts.