1 research outputs found
Spontaneous Chemical Ordering in Bimetallic Nanoparticles
In most experimental studies on bimetallic
nanoparticles the homogeneous
alloying is consistently reported or a priori assumed. It is generally
believed that at nanoscale, alloying is promoted even for otherwise
immiscible systems. In this study we present evidence that Pd–Pt
nanoalloys are much more susceptible to segregation than their bulk
counterparts. The spontaneous segregation (chemical ordering) of Pd–Pt
nanoalloys was evidenced in hydrogen absorption studies and additionally
confirmed by using X-ray photoelectron spectroscopy. The results clearly
show that phase segregation in bimetallic nanoparticles do occur despite
the lack of the miscibility gap in the Pd–Pt phase diagram,
negative heat of mixing and small lattice mismatch for both metals.
Phase segregation for other bimetallic systems is also discussed.
Hydrogen solubility in the investigated nanoparticles is enhanced
nearly by 3 orders of magnitude with respect to H solubility in unsegregated
Pd–Pt alloys. This superior solubility points out the importance
of phase segregation, which is frequently overlooked, yet fundamental
for systems designed for heterogeneous catalysis and hydrogen storage