Electron and configuration engineering of atomic Cu and multi-oxidated Cu₂₊₁O centers via gasifiable reductant strategy for efficient oxygen reduction toward Zn-air battery

Efforts in a large number of transition metal-carbon systems are devoted to the development of efficient catalysts for oxygen reduction reaction (ORR). However, unsatisfied O₂ adsorption and slow reduction of OH* at the active centers hinder the further development of these catalysts. We here report a gasifiable reductant strategy, of which a new Cu-based metal organic framework (MOF: termed NTU-83) nanosheet was co-pyrolyzed with melamine to produce the N-coordinated atomic Cu and multi-oxidated Cu₂₊₁O active centers on the carbon foam with ultrathin skeleton. The engineered electrons and configuration of the active centers boost the catalyst (Cu/NC-1000) to show superior ORR activity (E_1/2 = 0.85 V), excellent stability, and methanol resistance. Further modeling calculation and controlled experiments reveal that the Cu₂₊₁O species play a crucial role in kinetically accelerated adsorption and activation of O₂, while the N₄ coordinated atomic Cu facilitates fast reduction of OH*. Such characteristics endow the Zn-air battery that containing Cu/NC-1000 as air cathode to show a high peak power density (138 mW·cm⁻²), a high specific capacity of 763 mAh·g_Zn⁻¹, and outstanding long-term cycle stability. The plausible mechanism and excellent performance show that gasifiable reductant strategy opens up a new route for regulation of the electronic of active sites but also provides a candidate for the practical application in energy conversion/storage devices.