The limited durability of metal-nitrogen-carbon electrocatalysts severely restricts their applicability for the oxygen reduction reaction in proton exchange membrane fuel cells. In this study, we employ the chemical vapor modification method to alter the configuration of active sites from FeN to the stable monosymmetric FeN+N', along with enhancing the degree of graphitization in the carbon substrate. This improvement effectively addresses the challenges associated with Fe active center leaching caused by N-group protonation and free radicals attack due to the 2-electron oxygen reduction reaction. The electrocatalyst with neoteric active site exhibited excellent durability. During accelerated aging test, the electrocatalyst exhibited negligible decline in its half-wave potential even after undergoing 200,000 potential cycles. Furthermore, when subjected to operational conditions representative of fuel cell systems, the electrocatalyst displayed remarkable durability, sustaining stable performance for a duration exceeding 248 h. The significant improvement in durability provides highly valuable insights for the practical application of metal-nitrogen-carbon electrocatalysts.
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http://dx.doi.org/10.1038/s41467-024-47817-0 | DOI Listing |
Angew Chem Int Ed Engl
January 2025
Tianjin University, School of Materials science and engineering, School of Materials Science and Engineering, Tianjin University, 300072, Tianjin, CHINA.
Fe-N-C catalyst is the most promising alternative to platinum catalyst for proton-exchange membrane fuel cells (PEMFCs), however its high performance cannot be maintained for a long enough time in device. The construction of a new Fe coordination environment that is different from the square-planar Fe-N 4 configuration in Fe-N-C catalyst is expected to break current stability limits, which however remains unexplored. Here, we report the conversion of Fe-N-C to a new FeNxSey catalyst, where the Fe sites are three-dimensionally (3D) co-coordinated by N and Se atoms.
View Article and Find Full Text PDFRSC Adv
January 2025
Department of Physics and Chemistry, Faculty of Education, Alexandria University Egypt.
A novel series of azo dyes was successfully synthesized by combining amino benzoic acid and amino phenol on the same molecular framework azo linkage. The structural elucidation of these dyes was carried out using various spectroscopic techniques, including UV-vis, FT-IR, NMR spectroscopy, and HRMS. Surprisingly, the aromatic proton in some dyes exhibited exchangeability in DO, prompting a 2D NMR analysis to confirm this phenomenon.
View Article and Find Full Text PDFMagn Reson Med
January 2025
Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.
Purpose: To develop and evaluate a physics-driven, saturation contrast-aware, deep-learning-based framework for motion artifact correction in CEST MRI.
Methods: A neural network was designed to correct motion artifacts directly from a Z-spectrum frequency (Ω) domain rather than an image spatial domain. Motion artifacts were simulated by modeling 3D rigid-body motion and readout-related motion during k-space sampling.
ACS Appl Mater Interfaces
January 2025
School of Automotive Studies, Tongji University, Shanghai 201804, China.
Proton exchange membrane fuel cell (PEMFC) is considered the next promising generation of power devices for vehicles. The microporous layer (MPL) improves the performance through effective water management. In this study, local hydrophilic networks of nano- and macropores are formed in different MPLs.
View Article and Find Full Text PDFMagn Reson Med
January 2025
Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Purpose: To optimize a 100 ms pulse for producing CEST MRI contrast and evaluate in mice.
Methods: A gradient ascent algorithm was employed to generate a family of 100 point, 100 ms pulses for use in CEST pulse trains (proton resonance enhancement for CEST imaging and shift exchange). Gradient ascent optimizations were performed for exchange rates = 500, 1500, 2500, 3500, and 4500 s; and labile proton offsets (Δω) = 9.
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