Supplementary information files for "Nanoscale confinement‐induced atom‐milling Pd nano‐sheets into ultra‐fine Pd₃Co Alloys"

Atomic regulation of nanocatalysts is of both scientific and technological importance in efficient hydrogen energy conversion technology. Here a feasible nanoscale confinement‐induced atom‐milling (NCAM) method is reported to synthesize and atomically mesh 1 nm thick Pd metallic films into ultra‐fine Pd3Co nanoalloys. The nano‐sized inner space of layered crystalline provides a nano‐scaled limitation (1.3 nm) for atoms’ collision, which forces the assembly of hydrogen or Co atoms into a Pd lattice to expand or contract crystal as atom‐milling. The resulting ultra‐fine Pd3Co nanoalloys exhibit nearly three times higher activity than commercial Pt/C for oxygen reduction reaction, and 2.3 times higher activity than Pd/C for formic acid electrooxidation reaction, for fuel cells, and wider electrocatalysis applications.