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 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 43, 2015 

A publication of 

The Italian Association 
of Chemical Engineering 
Online at www.aidic.it/cet 

Chief Editors: Sauro Pierucci, Jiří J. Klemeš 
Copyright © 2015, AIDIC Servizi S.r.l., 
ISBN 978-88-95608-34-1; ISSN 2283-9216                                                                               

 

Electrochemical H2O2 Sensors Based on Au/CeO2 
Nanoparticles for Industrial Applications 

Claudio Ampelli*a, Salvatore G. Leonardib, Anna Bonavitab, Chiara Genovesea, 
Georgia Papanikolaoua, Siglinda Perathonera, Gabriele Centia, Giovanni Nerib 
aDep. of Electronic Engineering, Industrial Chemistry and Engineering, University of Messina, v.le F. Stagno d'Alcontres, 31 
- 98166 Messina, Italy 
bDep. of Electronic Engineering, Industrial Chemistry and Engineering, University of Messina, c.da di Dio - 98166 Messina, 
Italy 
ampellic@unime.it 

Gold-cerium oxide (Au/CeO2) composite was synthesized by a deposition-precipitation method and used to 
fabricate a highly sensitive non-enzymatic electrochemical sensor for hydrogen peroxide (H2O2) detection. 
The morphology and microstructure of the Au/CeO2 composite was characterized by transmission electron 
microscopy (TEM) and X-ray diffraction (XRD). UV-Vis spectroscopy showed a strong plasmonic absorbance 
(in the range of 500-650 nm) due to Au nanoparticles deposited onto the surface of ceria. Sensing tests 
carried out by cyclic voltammetry (CV) showed that the Au/CeO2-composite-modified screen-printed carbon 
electrode exhibited electrocatalytic response to H2O2. By chronoamperometry, a detection limit (S/N=3) as low 
as 5 μM and a sensitivity of 27.1 μA mM−1cm−2 were measured. These results open the route for a potential 
use of the fabricated Au/CeO2-based sensor to improve the H2O2 detection ability in many industrial fields. 

1. Introduction 

The analytical determination of hydrogen peroxide (H2O2) is of great importance in environmental, 
pharmaceutical and industrial fields (Kim et al., 2013). From municipal wastewater and drinking water 
treatments to gas, oil and petrochemical refinery applications, polymer product manufacture, wood pulp, paper 
and milling industries as a bleaching agent, H2O2 is playing a major role in the modern industrial world (Jones, 
1999). 
Electrochemical sensors for H2O2 detection are basically classified into two major categories: enzymatic and 
non-enzymatic sensors. Although enzyme-based electrochemical biosensors are still dominating, they are 
affected by temperature, pH and toxic chemicals (Ensafi et al., 2015). On the other hand, in recent years, 
nanomaterials have attracted great research interest because of their desirable chemical, physical and 
electronic properties that are different from those of bulk materials (Ampelli et al., 2014a). They have also 
attracted a remarkable interest for their simplicity and low cost (Ampelli et al., 2014b). The electrocatalytic 
properties of enzyme-free electrochemical sensors can be improved by using suitable nanomaterials to modify 
the working electrode, enhancing the current and decreasing the high over-potentials of many compounds 
which downgrade the sensing performance in common unmodified electrodes (Chen et al., 2013). 
A large range of nanomaterials such as metals, metal oxides, carbon nanotubes, graphene, and also 
nanocomposite materials, have been employed for electrocatalytic H2O2 detection (Leonardi et al., 2014). For 
example, Yi et al. (2011) fabricated H2O2 sensors based on highly ordered Ag-nanoparticle-decorated silicon 
nanowire arrays, obtaining favourable electrocatalytic performance due to their high electrical conductibility. 
Zhao et al. (2009) fabricated H2O2 sensors based on multiwalled carbon nanotubes/Ag nanohybrids modified 
gold electrode, obtaining high sensitivity and reducing interferences from other oxidizable species. Among the 
metal oxides, ceria (CeO2) is one of the most promising semiconductor oxide material for biosensor fabrication 
due to its excellent properties, including good biocompatibility, high chemical stability and excellent electronic 

                                

 
 

 

 
   

                                                  
DOI: 10.3303/CET1543123 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Ampelli C., Leonardi S., Bonavita A., Genovese C., Papanikolaou G., Perathoner S., Centi G., Neri G., 2015, 
Electrochemical h2o2 sensors based on au/ceo2 nanoparticles for industrial applications, Chemical Engineering Transactions, 43, 733-738  
DOI: 10.3303/CET1543123

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conductivity (Zhang et al., 2012). Ispas et al. (2008) prepared uniform colloidal ceria nanoparticles and 
described new possibilities of exploring the unique catalytic and redox properties of this material for the 
development of a simple enzymeless sensor for the determination of H2O2. Ujjain et al. (2014) prepared ceria 
nanoparticles by hydrothermal treatments using different capping agents. They found that CeO2-HMTA, 
synthesized by the use of hexamethylene-tetra-amine (HMTA), exhibited superior electrocatalytic activity 
toward H2O2 reduction, due to its better microstructural characteristics. Furthermore, by amperometric 
responses they measured a sensitivity of 27.1  μA  cm-2 mM-1. 
The presence of noble metal nanoparticles (NPs) may significantly improve the sensing performance (Ampelli 
et al., 2012). Au/CeO2 has shown a remarkable electrocatalytic activity towards some biomolecules such as 
dopamine (Tong et al., 2013). Au/CeO2/chitosan was used as enzymatic H2O2 sensor (Zhang et al., 2012) but, 
to the best of our knowledge, no noble-metal-doped CeO2 material was yet used as electrode for H2O2 
electrooxidation detection. 
In this contribution we report on the fabrication of H2O2 sensors based on Au NPs dispersed on CeO2 by a 
deposition-precipitation method. The electrochemical sensors were manufactured by printing Au/CeO2 
composites onto commercial carbon-based planar electrodes and tested by cyclic voltammetry in the 
presence of H2O2 to evaluate their electrochemical performances. The main aim is to fabricate an 
electrochemical sensor showing favourable electrocatalytic performances in terms of high sensitivity, facile 
preparation procedure, wide linear range, low limit of detection, long-term stability, satisfying reproducibility 
and anti-interference ability, providing a promising platform for non-enzymatic sensing of H2O2. 

2. Experimental 

2.1 Preparation and characterization of Au/CeO2 nanocomposite 

The electrode materials were prepared by depositing Au NPs onto commercial CeO2 (powder, supplied by 
STREM Chemicals) by a deposition-precipitation method (Signoretto et al., 2013). In particular, the oxide 
support was suspended in an aqueous solution of the Au precursor (HAuCl4·3H2O) for 3 h at pH 8.6. The pH 
was controlled and adjusted by adding NaOH (0.5 M). The sample was washed, filtered and dried at 35 °C for 
12 h and finally reduced at 200 °C. The final Au loading onto CeO2 was 1.5 wt. %. 
The sensing materials were characterized by X-Ray Diffraction (XRD) using a D2 Phaser Bruker 
diffractometer equipped with a Cu-Kα radiation source and operated at 30 kV and 10 mA. Data were collected 
at a scanning rate of 0.025° s-1 in a 2θ range from 12° to 100°. Transmission Electron Microscopy (TEM) 
images were acquired by the use of a Joel JEM 2010 electron microscope with an accelerating voltage of 200 
keV. Ultraviolet-visible diffuse reflectance spectra were recorded by a Jasco V570 spectrometer equipped with 
an integrating sphere for solid samples using BaSO4 as reference and in air. The particle size was calculated 
using the Scherrer equation. 

2.2 Preparation of Au/CeO2-modified electrode 

Water suspensions of the synthesized Au/CeO2 composites were mixed with Nafion (5 wt. %) and sonicated 
for 15 min in order to obtain a homogeneous dispersion. The suspensions were then printed on the working 
electrode of a disposable planar sensor (supplied by Dropsens) consisting of three electrodes, namely a 
carbon screen-printed working electrode (4 mm diameter), a carbon auxiliary electrode and a silver pseudo-
reference electrode. The printed sensors were then allowed to dry at room temperature. 

2.3 H2O2 sensing tests 

The electrochemical measurements were performed by means of a Dropsens µStat 400 potentiostat. The so-
fabricated sensors were characterized by cyclic voltammetry (CV) and chrono-amperometric tests in a pH 7.4 
phosphate buffer solution (PBS). CV tests were carried out at different scan rates (50-500 mV s-1) in the range 
of potentials between –0.8 V and 0.8 V, in the presence of different concentrations of H2O2 in PBS (0-25 mM). 
Chrono-amperometric curves were obtained recording the oxidation current at a fixed potential, while an 
appropriate volume of H2O2 solution was added into the PBS maintained under magnetic stirring conditions. 

3. Results and discussion 

3.1 Characterization of Au/CeO2 nanocomposite 

The morphology and size of the synthesized Au/CeO2 sample was elucidated by the TEM images shown in 
Figure 1. The TEM images of the composite sample show large aggregates of CeO2 nanoparticles. The 
aggregates are composed of grains with a prismatic-like shape and an average size of ~10-15 nm. 

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Figure 1: Representative TEM images of the Au/CeO2 sample. The inset in the figure on the left shows lattice 
fringes of the CeO2 nanoparticles 

The high-resolution image in the inset shows the lattice fringes of the CeO2 nanoparticles, suggesting their 
crystalline nature. Small gold NPs are also occasionally visible on the surface of the CeO2 grains. 
XRD gives information about the crystal structures and phase of the crystalline material synthesized. The 
general feature of the XRD patterns, in particular the presence of strong and sharp peaks, confirm that the 
CeO2 nanoparticles are crystalline (Figure 2a). The XRD spectra display sharp peaks situated at 2θ = 28.6, 
33.2, 47.5, 56.5, 59.2, 69.4, 76.7, and 79.1, which are corresponding to (111), (200), (220), (311), (222), (400), 
(331) and (420) planes, respectively. The values of d-spacing are in good agreement with that of CeO2 in its 
face-centred cubic phase (JCPDF cards no 75-8371) (Palard et al., 2010). The average diameter of CeO2, as 
calculated by the use of the Scherrer equation, is about 12.0 nm, which is in according with the TEM results. 
The XRD pattern of the composite sample also exhibits the characteristic peak of metallic Au at about 2θ = 
38.5. The peak of metallic Au shows a weak intensity, due either to the low Au loading (1.5 wt. %) or to low 
crystallinity. 
UV-Vis characterization has also been performed to get further information about the Au NPs supported on 
CeO2. Figure 2b shows the UV-visible diffuse reflectance spectrum of the Au/CeO2 sample (the spectrum of 
pure CeO2 is also shown as a comparison). The intense band below 400 nm is due to the typical absorption of 
the CeO2 semiconductor, while the broad band in the visible region (in the range of 500-650 nm) is attributable 
to the presence of Au NPs on the surface of ceria. It is well known that Au NPs absorb light in the visible 
region due to Localized Surface Plasmon Resonance (LSPR) effect. LSPR refers to the collective oscillation of 
free conduction band electrons of the Au NPs (Ampelli et al., 2014c). It is to remark that this band is not 
usually observed in gold bulk materials and that Au NPs deposited onto a CeO2 surface show very peculiar 
properties (Ampelli et al., 2014d). 

 

Figure: 2: a) XRD patterns and b) UV-Visible diffusive reflectance spectra of Au/CeO2 and CeO2 samples 

2θ, degree
20 40 60 80 100

In
te

n
si

ty
, 
a
.u

.

0

500

1000

1500

2000

CeO2 
Au/CeO2

Au

wavelenght, nm

300 400 500 600 700 800

F
(R

),
 u

.a
.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

CeO2
Au/CeO2

a) 

b) 

735



The strong plasmon resonance effect observed may be attributed to the interfacial interactions between Au 
and CeO2, resulting in the electron and energy transfer from the metal surface to the semiconductor material 
(Zhang et al., 2012). 

3.2 H2O2 sensing tests 

The synthesized Au/CeO2 composite was then used to modify the working electrode of a disposable carbon 
electrode and tested for the electrooxidation of H2O2. In order to evaluate the role of Au in the CeO2 matrix, 
CV experiments were first carried out on the bare carbon electrode and pure-CeO2-modified electrode. It was 
observed that both the bare carbon electrode (not shown) and pure CeO2 do not contribute to the 
electrooxidation activity towards this analyte in the operating conditions adopted. No evident current peaks, in 
fact, were observed at a potential of about 0.6 V (Figure 3a). This agrees with recent results reported by Ispas 
et al. (2008), who, investigating CeO2 nanoparticles for H2O2 detection at different pH, noted a higher 
electrocatalytic activity when working in alkaline medium than when the pH was nearly neutral. 
The CV of the Au/CeO2 nanocomposite in the presence of hydrogen peroxide shows instead a clear anodic 
peak at about 0.6 V (Figure 3a). Figure 3b shows the CV curves recorded at different scan rates from 25 to 
400 mV s-1, while the inset shows a plot of the peak current (at ~0.6 V) vs. the square root of the scan rate. A 
linear relationship between the peak current and the square root of the scan rate in this scan-rate range was 
obtained, indicating that the process of electrooxidation is controlled by diffusion. 

0.0 0.2 0.4 0.6 0.8
-10

0

10

20

30

40
 

C
u
rr

e
n
t 
(μ

A
)

Potential (V)

 AuCeO
2
    0 mM H

2
O

2

 AuCeO
2
    3 mM H

2
O

2

 CeO
2 
        0 mM H

2
O

2

 CeO
2  

       3 mM H
2
O

2

a)
0.0 0.2 0.4 0.6 0.8

0

20

40

60

80
C

u
rr

e
n
t 
(μ

A
)

Potential (V)

Scan rate

b)

5 10 15 20
10

20

30

40

C
u
rr

e
n
t 
(μ

A
)

Scan rate (mV/s)1/2

0,6 V

 

Figure 3: a) CVs of CeO2 nanoparticles and of Au/CeO2 nanocomposite in the absence and presence of 
hydrogen peroxide; b) CVs of Au/CeO2 nanocomposite in the presence of 3 mM hydrogen peroxide at 
different scan rates; inset in b) plot of the peak current vs. the square root of the scan rate 

0.0 0.2 0.4 0.6 0.8

0

10

20

30

40

C
u

rr
e

n
t 

(μ
A

)

Potential (V)

0 - 3 mM H
2
O

2

a)

0.0 0.5 1.0 1.5 2.0 2.5 3.0
0

4

8

12

16

20

C
u

rr
e

n
t 

(μ
A

)

H
2
O

2
 (mM)

b)

 

Figure 4: CVs of the Au/CeO2 nanocomposite in the presence of different concentrations of hydrogen 
peroxide; b) peak current as function of H2O2 concentration 

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0 10 20 30 40 50 60 70

0

10

20

30

40

50

60

70

80

90

C
u

rr
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n
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(μ
A

)

Time (min)

0.4 mM
2 mM

1 mM

6 mM

12 mM

25 mM

a)

0 100 200 300
0.0

0.1

0.2

0.3
 C

u
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(μ

A
)

Time (s)

50 μM

300 μM

0 5 10 15 20 25 30
-10

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(μ
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 (mM)

b)

0 100 200 300
0.05

0.10

0.15

0.20

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u
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e
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t 
(μ

A
)

H
2
O

2
 (μM)

 

Figure 5: a) Amperometric response at an applied potential of 0.6 V of the electrode modified with Au/CeO2; b) 
calibration curve 

Figure 4 shows the effect of H2O2 concentration on the CV pattern. When increasing the analyte concentration 
from 0 up to 3 mM, the anodic peak increases in intensity, suggesting the possibility of using electrochemical 
techniques for quantitative H2O2 detection. 
Chroamperometry was therefore used to test the detection of H2O2 with the fabricated electrode modified with 
Au/CeO2 composite. Figure 5a shows the amperometric response, obtained by successive addition of different 
aliquots of H2O2 at the constant potential of 0.6 V. The typical current-time curve shows a rapid and sensitive 
response of the modified electrode to the change in H2O2 concentration. The corresponding calibration curve 
(Figure 5b) exhibits an excellent linear response within range from 0 to 30 mM. Moreover, a detection limit of 5 
µM (based on S/N = 3) and a sensitivity of 27.1 A mM−1 cm−2 were measured. 
In order to explain the enhanced effect of the Au/CeO2 composite compared to CeO2 and to bare carbon 
electrode, we can consider: i) the electron-transfer ability of the Au/CeO2 composite and ii) the higher electro-
activity for H2O2 provided by the Au nanoparticles. Furthermore, in general, for noble-metal-loaded/metal 
oxides, the electrochemical properties largely depend on the preparation method, on the surface 
physicochemical properties and even on the thermal processes adopted. The CeO2 surface characteristics 
(such as exposed crystal facets, surface defects, etc.) should also be deeply considered. Meanwhile, the size 
of the noble metal clusters on the surface is also a crucial factor. Further investigations are planned in order to 
get a better understanding of the influence of all these variables on the electrocatalytic properties of the 
Au/CeO2 composite towards H2O2. 

4. Conclusions 

In this contribution we reported on the fabrication of H2O2 sensors based on Au nanoparticles dispersed on 
CeO2 by a deposition-precipitation method. The electrochemical sensor was manufactured by printing the 
Au/CeO2 composites onto commercial carbon-based planar electrodes and tested by cyclic voltammetry in the 
presence of H2O2 to evaluate its electrochemical performances. 
The results showed that the fabricated sensor displayed good performance in terms of sensitivity and linear 
response, for the detection of H2O2. An anodic peak current was observed on the Au/CeO2 modified electrode 
as opposed to the unmodified carbon electrode, which was ascribed to the better electron-transfer ability 
and/or the higher electro-activity provided by the Au/CeO2 hybrid composite sensing layer. The developed 
enzyme-free Au/CeO2 sensor exhibited a linear response to H2O2 in the range investigated (0-3 mM) with a 
sensitivity of about 27.1 µA mM-1 cm-2, which is suitable for a variety of industrial applications. 
 
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