Enhanced cobalt porphyrin-catalytic oxygen reduction reactions by introducing benzoyloxy substitutes

Three novel triphenylamine (TPA) cobalt porphyrins Ph-TPACoP, FP-TPACoP and BA-TPACoP are designed to explore their efficacy in electrocatalytic oxygen reduction reactions (ORRs). The porphyrins are coated on carbon nanotubes and carbon black to construct composites for ORRs in alkaline and acidic media. The BA-TPACoPbased composites, on either carbon support and in either electrolyte, exhibit the best ORR performance among the catalysts under the same conditions. Remarkably, BA-TPACoP/CNT attains comparable reduction potentials and response current densities to Pt/C in alkali, and it also exhibits an electron transfer number of 3.94 in acid, reaching close to the 4-electron oxygen reduction. This work demonstrates the efficacy of benzoyloxy substitutes for the ORR improvement and may provide an applicable protocol for engineering efficient metalloporphyrins as electrocatalysts.