Giving Electrocatalysts an Edge Platinum (Pt) is an excellent catalyst for the oxygen-reduction reaction (ORR) in fuel cells and electrolyzers, but it is too expensive and scarce for widespread deployment, even when dispersed as Pt nanoparticles on carbon electrode supports (Pt/C). Alternatively, Chen et al. (p. 1339 , published online 27 February; see the Perspective by Greer ) made highly active ORR catalysts by dissolving away the interior of rhombic dodecahedral PtNi ₃ nanocrystals to leave Pt-rich Pt ₃ Ni edges. These nanoframe catalysts are durable—remaining active after 10,000 rounds of voltage cycling—and are far more active than Pt/C.