The rigidity of self-assembled cofacial porphyrins influences selectivity and kinetics of oxygen reduction electrocatalysis

Abstract

We report the electrocatalytic Oxygen Reduction Reaction on a rigid Co(II) porphyrin prism scaffold bridged by Ag(I) ions. The reactivity of this scaffold differs significantly from previous prism catalysts in that its selectivity is similar to that of monomer (∼35% H₂O) yet it displays sluggish kinetics, with an order of magnitude lower k_s of ∼0.5 M⁻¹ s⁻¹. The deleterious cofacial effect is not simply due to metal–metal separation, which is similar to our most selective prism catalysts. Instead we conclude the structural rigidity is responsible for these differences.