Silver-platinum alloy at the nanoscale
In order for two metals can form an alloy, it is required that such material is in liquid phase. However, not always the metals in a liquid phase can form alloys. When this happens, a miscibility gap is formed. The binary phase diagram (adapted from Massalski, T. B.; Murray, J. L.; Bennett, et al. Binary Alloy Phase Diagrams. American Society for Metals: Metals Park, Ohio, 1986.) illustrates the ratio between silver and platinum in terms of temperature. The miscibility gap appears to temperatures above 400 oC between Ag2Pt98 and Ag95Pt5. Recent research has shown that the nanoscale materials are capable to reduce the miscibility gap for the same temperature conditions with respect to macroscale.
Thus, in the case of silver and platinum, has succeeded in producing alloy nanoparticles formed by these two metals at room temperature. The walls of these nanoparticles are formed by a Ag/Pt alloy while a layer of platinum on the surface is achieved with a high crystallographic index. As is well known, this condition gives the particle high catalytic capacity. These results allow, among other important applications, the manufacture of electrodes for fuel cells with reduced amounts of platinum and suitable morphology to increase the catalytic activity.
González, E.; Merkoci, F.; Arenal, R. et al. Enhanced reactivity of high-index surface platinum hollow nanocrystal. J. Mater. Chem. A. 4 (2016) 200-2008.