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Bypassing Formation of Oxide Intermediate via Chemical Vapor Deposition for the Synthesis of an Mn-N-C Catalyst with Improved ORR Activity

[Image: see text] A significant barrier to the commercialization of proton exchange membrane fuel cells (PEMFCs) is the high cost of the platinum-based oxygen reduction reaction (ORR) cathode electrocatalysts. One viable solution is to replace platinum with a platinum-group metal (PGM) free catalyst...

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Detalles Bibliográficos
Autores principales: Stracensky, Thomas, Jiao, Li, Sun, Qiang, Liu, Ershuai, Yang, Fan, Zhong, Sichen, Cullen, David A., Myers, Deborah J., Kropf, A. Jeremy, Jia, Qingying, Mukerjee, Sanjeev, Xu, Hui
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2023
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10660335/
https://www.ncbi.nlm.nih.gov/pubmed/38026812
http://dx.doi.org/10.1021/acscatal.3c01982
Descripción
Sumario:[Image: see text] A significant barrier to the commercialization of proton exchange membrane fuel cells (PEMFCs) is the high cost of the platinum-based oxygen reduction reaction (ORR) cathode electrocatalysts. One viable solution is to replace platinum with a platinum-group metal (PGM) free catalyst with comparable activity and durability. However, PGM-free catalyst development is burdened by a lack of understanding of the active site formation mechanism during the requisite high-temperature synthesis step, thus making rational catalyst design challenging. Herein we demonstrate in-temperature X-ray absorption spectroscopy (XAS) to unravel the mechanism of site evolution during pyrolysis for a manganese-based catalyst. We show the transformation from an initial state of manganese oxides (MnO(x)) at room temperature, to the emergence of manganese-nitrogen (MnN(4)) site beginning at 750 °C, with its continued evolution up to the maximum temperature of 1000 °C. The competition between the MnO(x) and MnN(4) is identified as the primary factor governing the formation of MnN(4) sites during pyrolysis. This knowledge led us to use a chemical vapor deposition (CVD) method to produce MnN(4) sites to bypass the evolution route involving the MnO(x) intermediates. The Mn-N-C catalyst synthesized via CVD shows improved ORR activity over the Mn-N-C synthesized via traditional synthesis by the pyrolysis of a mixture of Mn, N, and C precursors.