Ultrathin 2D catalysts with N-coordinated single Co atom outside Co cluster for highly efficient Zn-air battery

Zn-air battery (ZAB) has been considered as a kind of important mobile energy system. However, one of the major challenges is to improve the efficiency of involved oxygen reduction reaction (ORR), which requires stable and highly effective electrocatalysts that may work with air as O2 supplier. Herein, we report the design and synthesis of a group of ultrathin 2D electrocatalysts (8.2 to 18.5 nm) from a new metal-organic framework (MOF) ([Co2(TCPP)(DABCO)], named NTU-70) that can be facilely prepared in large-scale. Compared with its block counterpart and other ultrathin electrocatalysts, Co@N-C700 exhibits superior ORR activity (E1/2 = 0.78 V) and outstanding durability, which originates from the synergistic effect of N-coordinated single Co atom outside Co cluster and ultrathin porous carbon support. Encouragingly, a rechargeable ZAB assembled with Co@N-C700 air cathode delivers a steady discharge voltage plateau of 1.22 V and a low discharge/charge polarization (0.80 V) within 240 h, outperforming Pt/C catalysts. The current strategy for finely design and synthesis of MOF-derived ultrathin electrocatalysts provides a prospect in developing metal-air batteries with a higher power density and may also pave the way for the feasible application of these ultrathin catalysts in energy conversion/storage devices.