A Fe-Ni-Zn triple single-atom catalyst for efficient oxygen reduction and oxygen evolution reaction in rechargeable Zn-air batteries.

[Display omitted] • A Fe-Ni-Zn triple single atom catalyst is an excellent bifunctional catalyst for ORR and OER. • XAS and TEM studies confirm Fe, Ni and Zn SAC atomically dispersed in the matrix. • The SAC(Fe,Ni,Zn) with an optimal Fe/Ni ratio of 5:5 is used for ZAB. • The battery has good specific capacity(809 mAh/g @ 50 mA cm−2) and excellent power density of 300 mW cm−2 @ 406 mA cm−2. • A rechargeable Zn-air battery has superior cycle stability with 2150 cycles (358.3 h). The rechargeable Zn-air battery (ZAB) is a promising device for energy storage. A good bifunctional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a decisive role in the ZAB. Here, we prepare a Fe-Ni-Zn triple single-atom catalyst (SAC) anchored in the nitrogen-doped porous carbon framework (NC) denoted as SAC(Fe, Ni, Zn)/NC or A-SAC(Fe, Ni, Zn)/NC (ammonia-treated) for the ZAB study. We found that not only Fe-N x , Ni-N x , and Zn-N x act as excellent catalytic sites for ORR and OER, but the synergetic effect by the three adjacent SAC(Fe, Ni, Zn) in the NC enhances the catalytic performance. As a result, the voltage difference (ΔE) of 0.75 V is achieved (half-wave potential of ORR: 0.88 V and the potential of OER at 10 mA cm−2: 1.63 V). In the rechargeable ZAB study, the battery with the A-SAC(Fe, Ni, Zn)/NC has a good specific capacity of 809 mAh/g @ 50 mA cm−2, the excellent power density of 300 mW cm−2 @ 406 mA cm−2 and superior cycle stability (2150 cycles, 358.3 h @ 10 mA cm−2) while the all-soild-state ZAB showed promising power density of 64.5 mW cm−2 and acceptable cycling durability over 25 h@1 mA cm−2. Triple SAC(Fe, Ni, Zn) in the hierarchical porous NC possesses the bifunctional catalytic capability, high ionic diffusivity, and electron conductivity. [ABSTRACT FROM AUTHOR]