Controllable Synthesis of Metal Nanoparticles for Electrocatalytic Activity Enhancement - Atomically-Precise Methods for Synthesis of Solid Catalysts - page 240

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Figure 9.11 TEM images of (a) 8 nm, (b) 5 nm, and (c) 12 nm Co 60 Pd 40 NPs (scale
bar ¼ 25 nm). (d) EDS elemental maps for Co (red) and Pd (blue) within
two individual 8 nm Co 60 Pd 40 NPs indicating the distribution of the two
elements within each NP. (e) NP mass current densities vs. applied
potential in 0.1 MHClO 4 and 2 M HCOOH at 25 1C(scanrate:50mVs 1 ).
Reprinted from ref. 62 with permission by American Chemical Society.

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oxidation. 61 Inspired by the MOR, one strategy to achieve FAOR activity
enhancement is to incorporate an early transition metal (M) into the Pd
structure to make MPd alloys, because the oxophilic property of M in the
alloy structure which should benefit the CO removal. Recently, the synthesis
of monodisperse CoPd NPs by co-reduction of Co(acac) 2 and PdBr 2 at 260 1C
in OAm and trioctylphosphine (TOP) was reported. 62 NP sizes were con-
trolled to be 5 to 12 nm by either the heating ramp rate or metal salt con-
centration (Figure 9.11a-d), and NP compositions ranging from Co 10 Pd 90 to
Co 60 Pd 40 were tuned by metal molar ratios. It represents a general approach
to Pd-based bimetallic NPs and could also be extended to make CuPd NPs
when Co(acac) 2 was replaced by Cu(ac) 2 . The 8 nm CoPd NPs show com-
position dependent FAOR activity with Co 50 Pd 50 4Co 60 Pd 40 4Co 10 Pd 90 4Pd
(Figure 9.11e).

9.4.2.2 Intermetallic NP Catalyst for FAOR
As discussed in Section 9.4.1.1, the chemical structure of the alloy NPs is of
great importance towards the activity and stability enhancement in elec-
trochemical

reactions. Recently, the tetragonal FePt/PtAu NPs were