Tailoring Oxygen Reduction Reaction Pathway on Spinel Oxides via Surficial Geometrical-Site Occupation Modification Driven by the Oxygen Evolution Reaction.

Abstract

The oxygen reduction reaction (ORR) has been demonstrated as a critical technology for both energy conversion technologies and hydrogen peroxide intermediate production. Herein, an in situ oxygen evolution reaction (OER) surface evolution strategy is applied for changing the surface structure of MnCo2 O4 oxide with tetrahedral and octahedral cations vacancies to realize reaction pathway switching from 2e- ORR and 4e- ORR. Interestingly, the as-synthesized MnCo2 O4 -pristine (MnCo2 O4 -P) with the highest surficial Mn/Co octahedron occupation favors two electrons reaction routes exhibiting high H2 O2 selectivity (≈80% and reaches nearly 100% at 0.75V vs RHE); after surface atoms reconstruction, MnCo2 O4 -activation (MnCo2 O4 -A) with the largest Mn/Co tetrahedron occupation present excellent ORR performance through the four-electron pathway with an ultrahigh onset potential and half-wave potential of 0.78 and 0.92V, ideal mass activity (MA), and turnover frequencies (TOF) values. Density functional theory (DFT) calculations reveal the concurrent modulations of both Co and Mn by the surface reconstructions, which improve the electroactivity of MnCo2 O4 -A toward the 4e- pathway. This work provides a new perspective to building correlation of OER activation-ORR property, bringing detailed understating for reaction route transformation, and thus guiding the development of certain electrocatalysts with specific purposes.