Monodispersed, ultrathin NiPt hollow nanospheres with tunable diameter and composition via a green chemical synthesis

Monodispersed NiPt hollow nanospheres with citric acid as surfactant were synthesized by a one-pot wet chemical method in water at room temperature. The diameter is adjustable from 13 to 100 nm with the shell thickness of 2–3 nm, roughly the size of nanocrystallites. The composition is also tunable with the ratio of Ni : Pt from 1 : 9 to 9 : 1. A phase formation mechanism is proposed for the controllability of the diameter from the sacrificial templates of intermediate Ni–B amorphous nanocompounds. Molecular dynamic calculations show that 2 nm is the lower-bound shell thickness for a stable hollow spherical structure to avoid distortion or collapse. Electrocatalytic properties for the oxidation of ethylene glycol are measured for 35 nm Ni50Pt50 hollow nanospheres. Its performance is apparently better than that using commercial Pt/C catalyst. This makes it a potential application as a fuel cell catalyst.