Tuning ORR selectivity of π-conjugated cobalt corroles from 2e- to 4e-
He Sun, Houssein Awada, Haitato Lei, Abdalaziz Aljabour, Luyang Song, Simon Offenthaler, Rui Cao, Wolfgang Schöfberger
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.