Phase-Controlled Synthesis of Ru Nanocrystals via Template-Directed Growth: Surface Energy versus Bulk Energy

Despite the successful control of crystal phase using template-directed growth, much remains unknown about theunderlying mechanisms. Here, we demonstrate that the crystalphase taken by the deposited metal depends on the lateral size offace-centered cubic (fcc)-Pd nanoplate templates with 12 nmplates givingfcc-Ru while 18-26 nm plates result in hexagonalclosed-packed (hcp)-Ru. Although Ru overlayers with a metastablefcc- (high in bulk energy) or stablehcp-phase (low in bulk energy)can be epitaxially deposited on the basal planes, the latticemismatch will lead to jaggedhcp- (high in surface energy) andsmoothfcc-facets (low in surface energy), respectively, on the sidefaces. As the proportion of basal and side faces on the nanoplatesvaries with lateral size, the crystal phase will change depending on the relative contributions from the surface and bulk energies. ThePd@fcc-Ru outperforms the Pd@hcp-Ru nanoplates toward ethylene glycol and glycerol oxidation reactions