Donor-π-acceptor cobalt porphyrins for electrocatalytic oxygen reduction reaction in acidic medium

Donor-pi bridge-acceptor (D-pi-A) design principle has been widely employed to build functionalized materials with excellent optical properties, whereas its feasibility in electrocatalytic reactions is seldom investigated. We demonstrate the primary study of D-pi-A rule in constructing electrocatalysts for oxygen reduction reaction (ORR) purpose by rationally designing three cobalt porphyrins EGZ1-3 with 9H-carbazole, triphenylamine and N,N-diphenyl-[1,1'-biphenyl]-4-amine as the donor substituents, respectively, cobalt porphyrin as the pi bridge, and cyanoacrylic acid as the acceptor unit. The electronic properties of the molecules are calculated using the density functional theory and the composite catalysts EGZs/C are characterized by a series of spectroscopic approaches. The electrochemical measurements show that EGZ3/C attains a more positive reduction potential and a greater response current density than EGZ1/C and EGZ2/C, which is possibly due to the optimized electronic structure and the substituent effect. The electron transfer number as well as hydrogen peroxide generation yield values suggest slightly better selectivity of EGZ3/C and EGZ2/C than those of EGZ1/C (i.e., similar to 2.9, similar to 2.9 vs. similar to 2.7 and similar to 54%, similar to 53% vs. similar to 62%, respectively) towards full oxygen reduction. Our result reveals the feasibility of the D-pi-A design rule and the importance of molecular electronic state and the substituent feature in constructing ORR electrocatalysts. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

The feasibility of the D-pi-A design rule in constructing electrocatalysts for oxygen reduction reaction (ORR) is investigated. Rational design of the molecular structure with appropriate donor, pi bridge, and acceptor units leads to composite catalysts with excellent electrocatalytic performance.