Tailoring the cobalt porphyrin for minimal overpotential in the electrochemical oxygen evolution/reduction reactions: A density functional study

Abstract

Oxygen reduction and evolution reactions (ORR/OER) have attracted tremendous attention as the means to provide sustainable energy solutions. Bifunctionality for ORR and OER is extremely crucial and relevant for regenerative fuel cell technology. Both reactions use precious metal-based electrocatalysts that are limited and expensive making a strong case to develop low-cost, active and stable electrocatalysts. We propose tailoring of Cobalt Porphyrin (Co–Pr) framework by introducing meso phenyl substituents in the Pr ligand and further substitution of phenyl group by ortho/para-anilino groups (CoTPP, CoTPP-o-NMe3, CoTPP-p-NMe3) to design an efficient and selective bifunctional catalyst. Electrocatalysis by CoTPP-o-NMe3 (ηORR/ηOER = 0.45/0.28 V) outperforms Ir/Ru and Pt based benchmark catalysts. Energy profile, scaling relationship, electrode potential, energy descriptor and FMO analysis performed in the DFT framework rationalize its excellent catalytic activity and selectivity for 4e− reduction of O2 to H2O which is vital for hydrogen production and fuel cell applications.