Metal-doped imine frameworks for the oxygen reduction reaction in acidic media

• Published in: Journal of power sources 2023-09, Vol.578, p.233223, Article 233223
• Main Authors: Tolosana-Moranchel, Álvaro, García, Álvaro, García-Corral, Álvaro, Marco, José F., Pascual, L., Liuzzi, Dalia, Salam, Mohamed A., Ferrer, Pilar, Torrero, Jorge, Grinter, David C., Held, Georg, García Sánchez, Daniel, Friedrich, K. Andreas, Retuerto, María, Rojas, Sergio
• Format: Article
• Language: English
• ISSN: 0378-7753
• DOI: 10.1016/j.jpowsour.2023.233223

The overall performance of proton exchange membrane fuel cells is limited by the sluggish kinetics of the oxygen-reduction reaction (ORR). Among the most active PGM-free ORR electrocatalysts are metal-nitrogen-carbon (M-N-C), such as Fe–N–C. The Fe–N4 ensembles in these PGM-free catalysts, present in different configurations, are proposed to be the active sites for the ORR in acid. In this work, we have synthesized a Fe/N/C catalyst via thermal treatment of a polymeric CxNy precursor obtained by the wet-polymerization of melamine (a nitrogen rich molecule) and terephthaldehyde. The materials obtained (Im-FeNC-1HT and Im-FeNC-2HT) display high ORR activity in acid electrolyte compared to other Fe–N–C catalysts prepared with precursors different than 2-methylimidazole or ZIF-8. Characterization data indicate the formation of high- and low-spin Fe-Nx ensembles, with a site density of 4.4·1019 sitesFe·g−1 estimated by electrochemical stripping of NO. The ORR activity was evaluated in a RRDE configuration in 0.1 M HClO4 and in MEA configuration in a single cell. [Display omitted] •A high N/C ratio precursor such as melamine used to synthesize Fe–N–C catalysts.•FeN4C10 and FeN4C12 moieties formed during the synthesis.•Site Density of exposed Fe sites determined by in situ and ex situ analyses.•ORR activity demonstrated in RDE and MEA configurations.