Polypyrrole-assisted oxygen electrocatalysis on perovskite oxidesElectronic supplementary information (ESI) available: The details of the synthetic procedure, characterization and electrochemical performance, Table S1 and Fig. S1-S8. See DOI: 10.1039/c6ee03501a

• Main Authors: Lee, Dong-Gyu, Kim, Su Hwan, Joo, Se Hun, Ji, Ho-Il, Tavassol, Hadi, Jeon, Yuju, Choi, Sihyuk, Lee, Myeong-Hee, Kim, Chanseok, Kwak, Sang Kyu, Kim, Guntae, Song, Hyun-Kon
• Format: Article
• Language: English
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/c6ee03501a

Nitrogen-containing electrocatalysts, such as metal-nitrogen-carbon (M-N-C) composites and nitrogen-doped carbons, are known to exhibit high activities for an oxygen reduction reaction (ORR). Moreover, even if the mechanism by which nitrogen improves the activities is not completely understood, a strong electronic interaction between nitrogen and active sites has been found in these composites. Herein, we demonstrate a case in which nitrogen improves the electroactivity, but in the absence of a strong interaction with other components. The overpotentials of the ORR and oxygen evolution reaction (OER) on perovskite oxide catalysts were significantly reduced simply by mixing the catalyst particles with polypyrrole/carbon composites (pPy/C). Any strong interactions between pPy (a nitrogen-containing compound) and active sites of the catalysts are not confirmed. A scenario based on the sequential task allocation between pPy and oxide catalysts for the ORR was proposed: (1) molecular oxygen is incorporated into pPy as a form of superoxide (pPy + O 2 − ), (2) the superoxide is transferred to the active sites of perovskite catalysts, and (3) the superoxide is completely reduced along the 4e ORR process. The overpotentials of the oxygen reduction on perovskite oxide catalysts were significantly reduced simply by mixing the catalyst particles with polypyrrole/carbon composites (pPy/C).