High-entropy alloy (HEA) nanoparticles (NPs) have been
emerging
with superior compositional tunability and multielemental synergy,
presenting a unique platform for material discovery and performance
optimization. Here we report a synthetic approach utilizing hollow-carbon
confinement in the ordinary furnace annealing to achieve the nonequilibrium
HEA-NPs such as Pt0.45Fe0.18Co0.12Ni0.15Mn0.10 with uniform size ∼5.9
nm. The facile temperature control allows us not only to reveal the
detailed reaction pathway through ex situ characterization
but also to tailor the HEA-NP structure from the crystalline solid
solution to intermetallic. The preconfinement of metal precursors
is the key to ensure the uniform distribution of metal nanoparticles
with confined volume, which is essential to prevent the thermodynamically
favored phase separation even during the ordinary furnace annealing.
Besides, the synthesized HEA-NPs exhibit remarkable activity and stability
in oxygen reduction catalysis. The demonstrated synthetic approach
may significantly expand the scope of HEA-NPs with uncharted composition
and performance.