Pulsed-Flow Near-Critical and Supercritical Synthesis
of Carbon-Supported Platinum Nanoparticles and In Situ X‑ray
Diffraction Study of Their Formation and Growth
posted on 2015-01-27, 00:00authored byJian-Li Mi, Henrik F. Clausen, Martin Bremholm, Mette S. Schmøkel, Patricia Hernández-Fernández, Jacob Becker, Bo B. Iversen
The formation and growth of carbon
(C)-supported platinum (Pt)
nanoparticles in a high-temperature, high-pressure ethanol solution
have been studied by in situ synchrotron radiation powder X-ray diffraction
(PXRD). Supercritical synthesis is shown to be an efficient way to
prepare Pt nanoparticles, and the crystallite size of Pt nanoparticles
is much smaller when formed with supporting C material compared with
synthesis without C. On the basis of the time-resolved in situ PXRD
data, a surface stress of 2.65 N/m is derived from the size dependence
of the cell parameters. As proof of concept, C-supported Pt nanoparticles
were subsequently synthesized in a pulsed-flow supercritical reactor,
which offers complete control of the reaction temperature, pressure,
and residence time. Well-dispersed Pt nanoparticles decorated on the
supporting C material can be obtained by adjusting the reaction conditions,
and the electrocatalytic activity of the samples is explored. A mass
activity of 0.1209 A/mgPt at a potential of 0.9 V is obtained
for the products prepared at 400 °C for a residence time of 20
s. The pulsed-flow supercritical method is a facile method to synthesize
ligand-free C-supported Pt nanoparticles with high electrocatalytic
activity.