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. 2022 Nov 21;12(22):4093.
doi: 10.3390/nano12224093.

Ethanol Electrooxidation at 1-2 nm AuPd Nanoparticles

Juliette W Strasser  1 , Richard M Crooks  1
Affiliations

Ethanol Electrooxidation at 1-2 nm AuPd Nanoparticles

Juliette W Strasser et al. Nanomaterials (Basel). .

Abstract

We report a systematic study of the electrocatalytic properties and stability of a series of 1-2 nm Au, Pd, and AuPd alloy nanoparticles (NPs) for the ethanol oxidation reaction (EOR). Following EOR electrocatalysis, NP sizes and compositions were characterized using aberration-corrected scanning transmission electron microscopy (ac-STEM) and energy dispersive spectroscopy (EDS). Two main findings emerge from this study. First, alloyed AuPd NPs exhibit enhanced electrocatalytic EOR activity compared to either monometallic Au or Pd NPs. Specifically, NPs having a 3:1 ratio of Au:Pd exhibit an ~8-fold increase in peak current density compared to Pd NPs, with an onset potential shifted ~200 mV more to the negative compared to Au NPs. Second, the size and composition of AuPd alloy NPs do not (within experimental error) change following 1.0 or 2.0 h chronoamperometry experiments, while monometallic Au NPs increase in size from 2 to 5 nm under the same conditions. Notably, this report demonstrates the importance of post-catalytic ac-STEM/EDS characterization for fully evaluating NP activity and stability, especially for 1-2 nm NPs that may change in size or structure during electrocatalysis.

Keywords: alloy nanoparticles; electrocatalysis; energy dispersive spectroscopy; ethanol electrooxidation; gold nanoparticles; palladium nanoparticles; scanning transmission electron microscopy.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Size-distribution histograms and representative ac-STEM micrographs for conductive inks containing as-prepared (a,b) G6-OH(AuPd)309; (c,d) G6-OH(Au3Pd)309; (e,f) G6-OH(AuPd3)309; (g,h) G6-OH(Pd309); and (i,j) G6-OH(Au309) DENs. The scale bar is 10.0 nm.
Figure 2
Figure 2
EDS line scans and corresponding ac-STEM micrographs for conductive inks containing as-prepared (a,b) G6-OH(AuPd)309; (c,d) G6-OH(Au3Pd)309; and (e,f) G6-OH(AuPd3)309 DENs. The yellow arrow on each ac-STEM micrograph corresponds to the x-axis of the EDS line scan. The scale bar is 5.0 nm.
Figure 3
Figure 3
Electrocatalytic EOR CVs for (a) G6-OH(Pd309) and G6-OH(Au309); (b) G6-OH(AuPd)309; (c) G6-OH(Au3Pd)309; and (d) G6-OH(AuPd3)309 DENs. The CVs were carried out at a scan rate of 50 mV/s in a N2-satd., 1.0 M KOH solution containing 0.50 M ethanol. Electrocatalytic EOR CVs were background subtracted using the background CVs shown in Figure S1.
Figure 4
Figure 4
EDS line scans and corresponding ac-STEM micrographs for conductive inks containing (a,b) G6-OH(AuPd)309; (c,d) G6-OH(Au3Pd)309; and (e,f) G6-OH(AuPd3)309 DENs following EOR CVs. The CVs were carried out at a scan rate of 50 mV/s in a N2-satd., 1.0 M KOH solution containing 0.50 M ethanol. The yellow arrow on each ac-STEM micrograph corresponds to the x-axis of the EDS line scan. The scale bar is 5.0 nm.
Figure 5
Figure 5
Electrocatalytic EOR CAs for the indicated DENs. The CAs were carried out in a N2-satd., 1.0 M KOH solution containing 0.50 M ethanol, by holding the electrode potential for 1.0 h at the peak potential of the forward scan of the EOR CV. For clarity, the first 10 s of the CA are not shown in the figure.
Figure 6
Figure 6
Size-distribution histograms and ac-STEM micrographs for conductive inks containing (a,b) G6-OH(AuPd)309; (c,d) G6-OH(Au3Pd)309; (e,f) G6-OH(AuPd3)309; (g,h) G6-OH(Pd309); and (i,j) G6-OH(Au309) DENs after electrocatalytic EOR CAs. CAs were carried out in a N2-satd., 1.0 M KOH solution containing 0.50 M ethanol, by holding the electrode potential for 1.0 h at the peak potential of the forward scan of the EOR CV. The scale bar is 10.0 nm.
Figure 7
Figure 7
EDS line scans and corresponding ac-STEM micrographs for conductive inks containing (a,b) G6-OH(AuPd)309; (c,d) G6-OH(Au3Pd)309; and (e,f) G6-OH(AuPd3)309 DENs after a 1.0 h EOR CA. CAs were carried out in a N2-satd., 1.0 M KOH solution containing 0.50 M ethanol, by holding the electrode potential for 1.0 h at the peak potential of the forward scan of the EOR CV. The yellow arrow on each ac-STEM micrograph corresponds to the x-axis of the EDS line scan. The scale bar is 5.0 nm.
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