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Octahedral spinel electrocatalysts for alkaline fuel cells.
- Source :
- Proceedings of the National Academy of Sciences of the United States of America; 12/3/2019, Vol. 116 Issue 49, p24425-24432, 8p
- Publication Year :
- 2019
-
Abstract
- Designing high-performance nonprecious electrocatalysts to replace Pt for the oxygen reduction reaction (ORR) has been a key challenge for advancing fuel cell technologies. Here, we report a systematic study of 15 different AB<subscript>2</subscript>O<subscript>4</subscript>/C spinel nanoparticles with well-controlled octahedral morphology. The 3 most active ORR electrocatalysts were MnCo<subscript>2</subscript>O<subscript>4</subscript>/C, CoMn<subscript>2</subscript>O<subscript>4</subscript>/C, and CoFe<subscript>2</subscript>O<subscript>4</subscript>/C. CoMn<subscript>2</subscript>O<subscript>4</subscript>/C exhibited a half-wave potential of 0.89 V in 1 M KOH, equal to the benchmark activity of Pt/C, which was ascribed to charge transfer between Co and Mn, as evidenced by X-ray absorption spectroscopy. Scanning transmission electron microscopy (STEM) provided atomic-scale, spatially resolved images, and high-energy-resolution electron-loss near-edge structure (ELNES) enabled fingerprinting the local chemical environment around the active sites. The most active MnCo<subscript>2</subscript>O<subscript>4</subscript>/C was shown to have a unique Co-Mn core–shell structure. ELNES spectra indicate that the Co in the core is predominantly Co<superscript>2.7+</superscript> while in the shell, it is mainly Co<superscript>2+</superscript>. Broader Mn ELNES spectra indicate less-ordered nearest oxygen neighbors. Co in the shell occupies mainly tetrahedral sites, which are likely candidates as the active sites for the ORR. Such microscopic-level investigation probes the heterogeneous electronic structure at the single-nanoparticle level, and may provide a more rational basis for the design of electrocatalysts for alkaline fuel cells. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00278424
- Volume :
- 116
- Issue :
- 49
- Database :
- Complementary Index
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 140260032
- Full Text :
- https://doi.org/10.1073/pnas.1906570116