In situ small-angle x-ray scattering (SAXS) is used to investigate the electrochemical durability of Pt-Metal (Pt-M) catalysts sputtered onto nitrogen-modified high surface area carbon powder. The results demonstrate that nitrogen modification promotes catalyst durability through reduction of nanoparticle dissolution and coarsening. Although particle sizes of Pt-M on high surface area carbon supports can be difficult to determine with transmission electron microscopy (TEM), a novel SAXS method has been employed to calculate particle size. SAXS analysis shows that the Pt-M nanoparticle size distribution remained stable for 3000 electrochemical cycles after nitrogen modification, whereas the unmodified support material leads to Pt-M nanoparticle instabilities. These results for industrial-relevant catalyst/support architectures underscore the potential of nitrogen-modified carbon support structures for enhanced Pt-M catalyst durability. Read Paper