Tuning ORR selectivity of π-conjugated cobalt corroles from 2e- to 4e-

Abstract

Efficient oxygen reduction reaction (ORR) is crucial for the performance of fuel cells and other electrochemical devices. Seeking for stable and electrochemically selective 2e^- and 4e^- ORR electrocatalyst is yet a challenge, making the design extremely important and outmost of interest. In this study, we demonstrate a method to tune ORR selectivity by adjusting the local cobalt density through oligo-/polymerization of π-conjugated cobalt(III) A₂B and A₃-corroles to linear and two-dimensional matrix structures. These heterogeneous catalysts exhibit remarkable physicochemical properties, fast charge transfer kinetics, electrochemical reversibility, and high durability. Unselective three-electron transfer kinetics with n = 2.5–2.9 in between −0.20 V and +0.40 V vs. RHE are detected with the π-conjugated cobalt(III) A₂B- corrole polymers. Highly selective four-electron kinetics with n = 3.7 in between −0.20 V and +0.40 V vs. RHE are detected by employing the cobalt A₃-corrole oligomers during the ORR catalysis.