Boosting oxygen-reduction catalysis over mononuclear CuN2+2 moiety for rechargeable Zn-air battery

The molten salt assisted pyrolysis strategy is proposed to directly transform bulk metal into isolated single-atom sites, by which Cu-based single-atom catalyst can be prepared successfully and the catalyst demonstrates superior ORR activity as well as excellent Zn-air battery performance. • CuN 2+2 /C was prepared by molten-salt-assisted pyrolysis. • CuN 2+2 /C delivers remarkable alkaline ORR activity, outperforming that of Pt/C. • Excellent battery performance signifies the potential for practical applications. Endowing the transition-metal-nitrogen-carbon (M-N-Cs) electrocatalysts with high oxygen reduction activity for sustainable energy conversion, is a field of intense research while remains elusive. Here we exploit the variable configuration of atomically dispersed Cu 1 centers on carbon support via rationally constructing prototypical CuN 2+2 active sites to boost the kinetically sluggish electrochemical oxygen reduction. Density functional theory reveals the modified electronic structure of active Cu site and its derived orbital overlap through right symmetry with the degenerate π* orbital of O 2 molecule, which more effectively facilitates O 2 activation compared with CuN 4 counterpart. The targeted electrocatalyst delivers superior alkaline ORR activity with a half-wave potential of 0.88 V and superior kinetics with Tafel slope of 48 mV dec −1 , outperforming those of benchmark Pt/C. Remarkably, further demonstrated excellent peak power density and long-term durability in both primary liquid and flexible solid-state Zn-air battery assemblies signify the potential for practical applications.