Promoted O₂Activation at a Co^IIICenter for Significantly Improved Electrocatalytic Oxygen Reduction Reaction

Electrocatalytic oxygen reduction reaction (ORR) near its thermodynamic equilibrium potential is vital for efficient energy conversion. However, low-valent metal ions generated at high cathodic potentials are typically required to achieve effective O₂activation. Herein we report O₂activation promoted by a Sc³⁺-hung Co^IIIcorrole, which realizes markedly boosted ORR electrocatalysis. Co^IIIcorrole 1 with an appended crown ether substituent was synthesized. By grabbing a Sc³⁺ion, the ORR overpotential with Sc³⁺-hung 1 decreased by 1.0 V in acetonitrile and 170 mV in 0.5 M H₂SO₄solutions. Importantly, Sc³⁺-hung 1 achieved an ORR half-wave potential of 0.78 V vs RHE in 0.5 M H₂SO₄solutions with a transferred electron number of 3.87. Our results suggest that the hanging Sc³⁺promotes O₂binding and activation at the Co^IIIion of 1 to generate a Co^III–superoxo–Sc³⁺corrole cation radical and assists subsequent O–O bond cleavage by accepting the leaving hydroxide.