An activity lift for platinum Platinum is an excellent but expensive catalyst for the oxygen reduction reaction (ORR), which is critical for fuel cells. Alloying platinum with other metals can create shells of platinum on cores of less expensive metals, which increases its surface exposure, and compressive strain in the layer can also boost its activity (see the Perspective by Stephens et al. ). Bu et al. produced nanoplates—platinum-lead cores covered with platinum shells—that were in tensile strain. These nanoplates had high and stable ORR activity, which theory suggests arises from the strain optimizing the platinum-oxygen bond strength. Li et al. optimized both the amount of surface-exposed platinum and the specific activity. They made nanowires with a nickel oxide core and a platinum shell, annealed them to the metal alloy, and then leached out the nickel to form a rough surface. The mass activity was about double the best reported values from previous studies. Science , this issue p. 1410 , p. 1414 ; see also p. 1378

The energetics of nanoclusters is investigated for five different metals (Ag, Cu, Au, Pd, and Pt) by means of quenched molecular dynamics simulations. Results are obtained for two different semiempirical potentials. Three different structural motifs are considered: icosahedra (Ih), decahedra (Dh), and truncated octahedra (TO). The crossover sizes among structural motifs are directly calculated, considering cluster up to sizes N≃40 000. For all the systems considered, it is found that icosahedra are favored at small sizes, decahedra at intermediate sizes, and truncated octahedra at large sizes. However, the crossover sizes depend strongly on the metal: in Cu, the icosahedral interval is rather large, and it is followed by a very wide decahedral window; on the contrary, in Au, the icosahedral interval is practically absent, and the decahedral window is narrow. The other metals display intermediate behaviors, Ag being close to Cu, and Pd and Pt being close to Au. A simple criterion, which is based on the ratio between the bulk modulus and the cohesive energy per atom, is developed to account for the differences among the metals.