Functional materials 1 1.5 2 2.5 3 3.5 4 Dp nm Dp (nm) Pt Dp (nm) Pt3Co (nm) Pt (nm) Pt3Co 1 3 5 7 9 11 13 L nm L (nm) Pt L (nm) Pt3Co (nm) Pt (nm) Pt3Co (a) (b) Cathode in Cathode out Anode out Anode in Cathode in Cathode out Anode out Anode in Cathode in Cathode out Anode out Anode in Cathode in Cathode out Anode out Anode in Cathode in Cathode out Anode out Anode in Cathode in Cathode out Anode out Anode in Cathode in Cathode out Anode out Anode in Cathode in Cathode out Anode out Anode in Pt Pt3Co BoT EoT AST 1 BoT EoT AST 2 (c) Mass fractal Surface fractal (d) J.M. Edjokola1, M. Bogar2, H. Amenitsch3, V. Hacker1, M. Bodner1 1 Institute of Chemical Engineering and Environmental Technology, Graz University of Technology, Graz, Austria 2 Department of Engineering and Architecture, University of Trieste, Trieste, Italy 3 Institute of Inorganic Chemistry, Graz University of Technology, Graz, Austria e-mail: joel.edjokola@tugraz.at Acknowledgments This research receives funding from the Austrian Research Promotion Agency (FFG) under the AlpeDHues project (FFG 889328). We acknowledge the CERIC-ERIC consortium for access to the Austrian partner facility (Austrian SAXS beamline)@Elettra Sincrotrone Trieste and for the financial support. Original paper J.M. Edjokola et al., Small. 20, 2407591 (2024); DOI:10.1002/smll.202407591. Fig. 1 Figure 1. Structural evolution of Pt/C and Pt3Co/C electrocatalysts in proton exchange membrane fuel cells under accelerated stress testing (a) Mean particle diameter Dp and (b) Characteristic SAXS length L are shown across anode inlet(AI)/outlet(AO) position and cathode inlet (CI)/outlet (CO) positions for AST1 and AST2 protocols, highlighting coarsening in Pt/C and spatially heterogeneous fragmentation in Pt3Co/C. (c) Segmented current density distribution measurements reveal spatial variations in electrochemical performance that correspond to nanostructural degradation patterns. (d) Schematic representation of fractal evolution shows a transition from a mass fractal regime (dispersed network-like nanoparticle aggregates) to a surface fractal regime (smoother, denser aggregates) due to coarsening and densification during AST. Elettra Highlights 2024–2025 25
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