Controllable Synthesis of Metal Nanoparticles for Electrocatalytic Activity Enhancement - Atomically-Precise Methods for Synthesis of Solid Catalysts - page 241

developed as robust catalysts for FAOR. 63 In this study, the cubic solid so-
lution FePtAu NPs (denoted as fcc-FePtAu) were synthesized by co-reduction
of Pt(acac) 2 and HAuCl 4 A H 2 O and thermal decomposition of Fe(CO) 5 . The
composition of the FePtAu NPs was controlled by varying metal precursor
ratios. Thermal annealing in Ar þ 5% H 2 at 600 1C for 1 h led to the for-
mation of tetragonal FePtAu (denoted as fct-FePtAu) while annealing at
400 1C only led to the removal of the surfactant without causing the structure
change, as displayed in Figure 9.12a. To facilitate fcc-fct phase transfor-
mation, the Fe/Pt ratio was kept near 1 : 1, while Au was tuned with three
different percentages to demonstrate Au composition-dependent fcc-fct
transition and FAOR catalysis. Figure 9.12b shows the representative TEM
image of the monodisperse FePtAu NPs on Ketjen carbon. Analyses from
STEM-EELS and STEM-EDS indicated that in the fct-FePtAu, Au diffuses out
and distribute as clusters around the shell. Such a unique core-shell fct-
FePt/PtAu structure pattern is essential to demonstrate the enhanced activity
and durability for FAOR. Results on FAOR (Figure 9.12c and d) demonstrate
that the presence of surface Au alleviates the CO poisoning effect, as evi-
denced by the disappearance of the small peak at

d n 9 r 4 n g | 5

0.7 V. The much less
degree of CO poison observed on fct-FePt/PtAu than on Pt or FePt indicates
that Au on the NP surface is able to promote the dehydrogenation reaction of

B

.

Figure 9.12 (a) Schematic illustration of the structural change of the FePtAu NPs

upon annealing. When annealed at 400 1C, the FePtAu NPs have fcc
structure, but at 600 1C, the fct-FePtAu structure is formed, with Au
segregating on the NP surface. (b) TEM image of the fct-Fe 43 Pt 37 Au 20 /C
NPs. J-V curves of (c) the Fe 43 Pt 37 Au 20 NPs annealed at different
temperatures and (d) the specific activity of the fct-Fe 43 Pt 37 Au 20 , fct-
Fe 55 Pt 45 and commercial Pt catalysts in N 2 -saturated 0.5 M

H 2 SO 4 þ 0.5 M HCOOH solutions.
Reprinted from ref. 63 with permission by American Chemical Society.