Recent Developments in Gold Nanomaterial Catalysts for Oxidation Reaction through Green and Sustainable Routes - Advanced Materials for Agriculture, Food and Environmental Safety - page 217

( a )

1.5 1.0

positive scan
negative scan

positive scan
negative scan

1.0

0.5

0.5

( b )

0.0

0.0

-0.8 -0.4

E/V vs. Ag/AgCl

0.0 0.4 0.8 -0.8 -0.4

E/V vs. Ag/AgCl

0.0 0.4 0.8

( a ) ( b )

1.0

positive scan
negative scan

0.8

Cubic
Oct
RD

( c )

0.5

0.4

0.0

0.0

-0.8 -0.4 0.0 0.4 0.8 0 20 40 60

( c ) ( d )

t/s

E/V vs. Ag/AgCl

Figure 8.22 (let ) SEM images of the dif erently shaped Au polyhedra: (a) cubes, (b)
octahedra, (c) rhombic dodecahedra, and (right) Cyclic voltammograms of the dif erent
Au polyhedra on glassy carbon electrodes in a 0.1 M NaOH solution of 10 mM glucose at
a scan rate of 50 mV s1: (a) cubes, (b) octahedra, (c) dodecahedra. Dash lines represent
positive scanning and gray lines represent negative scanning. (d) Chronoamperometric
curves of dif erently shaped Au polyhedra toward glucose oxidation at 0.4 V vs Ag/AgCl.
Reproduced with permission from [110].

of the AuOH sites on the electrode surfaces increases) and 2.2 and 2.6 times
higher at 0.10 V (reduction of surface gold oxide and, thus, enough surface
active sites are available for the direct oxidation of glucose occurs). Armed
with both CV results, we can conclude that the electrocatalytic activities of
the dif erent Au polyhedra toward glucose oxidation are as follows: cubes
> rhombic dodecahedra ≈ octahedra.
Recently, Haruta et al. [111] developed a new preparation method, solid
grinding (SG), by using a volatile organogold complex, [Me 2 Au(acac)] (acac
= acetylacetonate), and succeeded in depositing small (2-4 nm) Au clusters
onto several kinds of metal oxides and carbon supports by this SG method,
and compared it with the conventional deposition-precipitation (DP) method.
h is study rel ects the importance of support and preparation method for oxi-
dation of glucose having a similar range of nanoparticles size (Figure 8.23).
h e highest catalytic activity was observed for Au/ZrO 2 (SG), with a
turnover frequency of 45 mol glucose mol surface Au -1 s -1 at 50 o C and pH 9.0. h e
catalytic activity of Au/Al 2 O 3 was comparable to that of Au/ZrO 2 (DP)
and slightly higher than that of Au/carbon at 70 ° C. However, Au/Al 2 O 3