Fig. 4: The demonstration that the alloy catalyst remained in realloyed state during and after accelerated durability test (ADT) in standard electrochemical cell and in PEMFC (in-situ/operando).

Experimental (black symbols) and RMC computed (red lines) atomic PDFs as well as the corresponding 3D RMC simulation models for a the as-prepared, and b the 20,000-cycled Pt₂₀Pd₂₀Cu₆₀/C catalyst. Upper and bottom panels show RMC models and atomic PDFs for Cu-core@PGM-shell and random alloy structures, respectively. Inset in b) is a magnified view of the data in the dash box for the experimentally-obtained first atomic PDF peak of as-prepared and cycled catalysts. c In operando HE-XRD patterns for Pt₂₀Pd₂₀Cu₆₀/C catalyst inside an operating PEMFC upon potential cycles. d Experimental (black symbols) and model-computed (red lines) atomic PDFs for Pt₂₀Pd₂₀Cu₆₀/C catalyst inside the PEMFC at 0, 1000, and 2000 cycles. e A close comparison of the experiment-obtained atomic PDFs at the low-r region (corresponding to the boxed regions in d). f Plots of lattice parameters obtained from the experimental and the calculated PDFs as a function of the potential cycle numbers.