Akademik Veri Yönetim Sistemi
Journal of the Electrochemical Society, cilt.164, sa.4, 2017 (SCI-Expanded, Scopus)
Solid-phase catalysts prepared by pyrolysis of Iron(II) phthalocyanine (FePC) embedded in high-surface carbons were evaluated for the catalysis of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Li+-conducting non-aqueous electrolytes. The ORR mechanism in high donor number (DN) dimethyl sulfoxide (DMSO)-based electrolytes is markedly different from that occurs in low DN acetonitrile(MeCN)-based electrolytes. The ORR is catalyzed by the reduced Fe(I) state of Fe(II)PC. Consequently, the Fe(II)PC/Fe(I)PC redox potential relative to O2 reduction potential in each electrolyte is important for ORR catalysis. In MeCNbased electrolytes, the Fe(I)PC catalyst is formed at a higher potential than the ORR potential. Hence the catalyzed ORR occurs at the inner-Helmholtz plane of the electrode, stabilizing the superoxide ion (O2-) formed by one-electron reduction of O2, as Fe(I)PC-O2-. Indeed, LiO2 was identified in the Raman spectra of cathodes from discharged Li-O2 battery cells. In DMSO-based electrolytes, the Fe(I)PC formation potential occurs below the ORR potential and accordingly LiO2 is more stable in its solvated state in the electrolyte solution as the Li(DMSO)n-O2- ion pair. This drives the ORR at the outer-Helmholtz plane of both catalyzed and uncatalyzed electrodes in DMSO-based electrolytes. The FePC embedded carbon electrode doubled the cycle life of Li-O2 cells utilizing low DN electrolytes.