Significantly boosted oxygen electrocatalysis with cooperation between cobalt and iron porphyrins

Abstract

Developing electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is of great importance. Herein, Co tetrakis(pentafluorophenyl)porphyrin (Co–P) and Fe chloride tetrakis(pentafluorophenyl)porphyrin (Fe–P) were loaded on carbon nanotubes (CNTs) for combining the electrocatalytic advantages of both Co–P and Fe–P. The resultant (Co–P)_0.5(Fe–P)_0.5@CNT composite displayed significantly boosted activity for the selective four-electron ORR with a half-wave potential of 0.80 V versus reversible hydrogen electrode (RHE) and for the OER with a potential of 1.65 V versus RHE to obtain 10 mA cm⁻² current density in 0.1 M KOH. A Zn–air battery assembled from (Co–P)_0.5(Fe–P)_0.5@CNT exhibited a small charge–discharge voltage gap of 0.74 V at 2 mA cm⁻², a high power density of 174.5 mW cm⁻² and a good rechargeable stability (>120 cycles).