Oberflächenanalyse N. M. Markovic et al. schildern in der Zuschrift auf wie sich die Sauerstoffentwicklungsaktivität von Dimetalloxidmaterialien durch Erzeugung nanosegregierter Domänen der Elemente an der Oberfläche einstellen lässt.
This document provides CIE recommended reference solar spectra for industrial applications. It contains a large selection of simulation benchmarks for total, direct and diffuse components of solar spectra under various atmospheric conditions and solar geometries (defined by the air mass). For this purpose a freely available solar spectral irradiance model has been used to generate tables and figures of solar spectral irradiance under a number of different atmospheric conditions, in the form of explicit meteorological input parameters. The data as provided in this document are to a large extent comparable to those in CIE 085-1989, but they are presented with a higher spectral sampling. The respective solar spectra are the basis for national and international standard reference spectra for various applications. They have been extensively validated against measured spectra. Keywords: daylight, irradiance, simulated solar radiation, solar radiation
Fe-N-C catalysts, the most promising platinum group metal (PGM)-free oxygen-reduction catalysts, often simultaneously contain pyrrolic N- (S1) and pyridinic N (S2) -coordinated FeN4 sites. These two types of active sites show significantly different intrinsic activity and stability. S1 sites are more active but less stable compared to S2 sites. Designing a Fe-N-C catalyst, which exclusively contains active S1 sites with enhanced intrinsic stability, is highly desirable to break the activity-stability trade-off. Herein, we report a Fe-N-C model catalyst that solely comprises S1 sites prepared by adding H2 in the pyrolysis atmosphere (i.e., 10% H2/Ar). A membrane electrode assembly (MEA) with the Fe-N-C cathode demonstrated compelling activity and generated a current density of 50.8 mA cm−2 at 0.9 ViR-free (H2-O2) and 211 mA cm−2 at 0.8 V (H2-air), which have significantly exceeded the U.S. DOE 2025 targets. The highly active Fe-N-C catalyst also demonstrated improved stability during life tests and accelerated stability tests (ASTs). The knowledge obtained from experimental and theoretical results elucidates that the FeN4 site formation process can be controlled by thermal activation atmospheres, which is essential to breaking activity-stability trade-off and design viable Fe-N-C catalysts with adequate activity and stability for proton exchange membrane fuel cells.
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