SYNTHESIS AND CHARACTERIZATION OF NANO CuO-ZrO2 MIXED OXIDE

R.R.Muthuchudarkodi1,a and C.Vedhi2,b

1Department of Chemistry, V.O Chidambaram College, Tuticorin –628008, Tamilnadu, INDIA 2Department of Chemistry, V.O Chidambaram College, Tuticorin –628008, Tamilnadu, INDIA

amuthu.rajaram@gmail.com ,bcvedhi@rediffmail.com

Keywords: Nano copper oxide, Nano Zirconium oxide, CuO-ZrO2, EDAX, Cyclic Voltammetry

ABSTRACT

Nano CuO-ZrO2 mixed oxides were prepared by wet chemical method by mixing equimolar

solutions (0.45M) of cupric chloride (1.92g) and Zirconium oxychloride (3.63g) in aqueous Sodium

hydroxide and refluxed at elevated temperature. The prepared nano CuO-ZrO2 mixed oxides were

characterized by FT-IR, SEM, EDAX, XRD, DSC and CV studies. From XRD studies the size of

the nano CuO and ZrO2 are found to be 25 and 9.5nm respectively through Debye-Scherrer's

formula. The sizes of the CuO-ZrO2 mixed oxide particles have also been characterized and the

average grain size of the particles is found to be 24nm in diameter. The nano particle composition

and morphology of CuO, ZrO2 and mixed oxide have been analysed by EDAX set up attached with

scanning electron microscope (SEM). EDAX analysis indicates the presence of Cu, Zr and O. SEM

morphological studies of CuO, ZrO2 and mixed CuO-ZrO2 revealed the particle distribution with

uniform granular structure. Cyclic Voltammetric studies exhibit good adherent behaviour on

electrode surface and good electroactivity at pH 1.0. Nano CuO, ZrO2 and mixed CuO-ZrO2 under

goes oxidation at 0.224V, 0.092V -0.072V and0.198V respectively. DSC thermogram of CuO, ZrO2

and mixed CuO-ZrO2 are recorded at the heating rate of 10o/ min. The glass transition temperature

(Tg), the crystallization temperature (Tc) and melting point (TM) of the mixed oxide are determined

from the DSC curve. The Tg value of CuO-ZrO2 mixed oxide is -50o C the Tc value is 20

o C and

melts at a temperature of 116o C.

INTRODUCTION

Metal oxide nanoparticles are a versatile material with many scientific and industrial

applications [1]. Among the recent developments in materials science nano-particles and nano-

composites have assumed high importance due to unique features associated with their size [2]. To

mention a few, a shift in the absorption edge in semiconductors, an enhanced catalytic activity, an

increase in magnetic moment, etc., are all size dependent, especially when the particles are of nano-

scale dimensions [3,4]. CuO is a p-type semiconductor with direct band gap and high absorption

properties that makes it a promising material for low cost photovoltaic cells. CuO nanoparticles are

used in a wide range of applications such as gas sensors, magnetic storage media, solar energy

transformation, semiconductors and organic catalysis. [5-11]. Zirconia supported copper catalysts

have been shown to have high activities and selectivities for NO-CO reactions at low temperature to

be active in the decomposition of N2O [12] and are active and selective for methanol synthesis from

carbon dioxide.[11,12-14]. Copper–zirconia catalysts can be prepared using a variety of wet-

chemical methods including sol–gel,[11] impregnation,[15] and co-precipitation

[12,13,15].Wambach et al.[17] have recently reviewed the preparation of metal–zirconia catalysts

along with their structural and chemical characteristics, and the catalytic properties for carbon

dioxide hydrogenation. Zirconia is useful in its stabilized state. Stabilized Zirconia is used in

Oxygen sensors and fuel cell membranes because it has the ability to allow oxygen ions to move

freely through the crystal structure at high temperature. This high ionic conductivity makes it one of

the most useful electroceramics. It is an important dielectric material and has potential application

as insulators in transistors in future nanoelectronic devices. In this study an attempt was made to

synthesize at elevated temperature new mixed nano oxides based on ZrO2.

Advanced Materials Research Vol. 678 (2013) pp 50-55Online available since 2013/Mar/25 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.678.50

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EXPERIMENTAL

Materials

The precursor of Zirconiumoxychloride (ZrOCl2), Copper salt (CuCl2), and the precipitant

(NaOH) were purchased from Aldrich. All solutions were made up with deionised water.

Preparation of nano metal oxides

50mL of 0.1M CuCl2 was added drop wise to an aqueous solution of NaOH (50mL, 1M),

making a final volume of 100mL. The mixture was stirred well and refluxed at an elevated

temperature for two hours. The sample was collected by centrifugation, washed with water and

dried over 2-4 days at room temperature. Similar procedure was carried out for the preparation of

ZrO2 nanoparticles using ZrOCl2.

Preparation of nano CuO-ZrO2 mixed Oxide

Nano CuO-ZrO2 mixed Oxide was prepared by wet chemical method. In this method 25mL

of 0.45M ZrOCl2 was added to the aqueous solution of 50mL of 1M NaOH and stirred well. To this

mixture 25mL of 0.45M CuCl2 was added making a final volume of 100mL. The resulting mixture

was stirred well and refluxed at elevated temperature for 2 hours. The sample was collected by

centrifugation, washed with water and dried over 2-4 days at room temperature.

RESULT AND DISCUSSION

FTIR spectral studies

Metal Oxides generally give absorption bands below 1000cm-1

that arise from interatomic

vibrations. The frequencies observed at 415-811cm-1

and 425-964cm-1

corresponds to Cu-O and Zr-

O bond vibrations respectively. Symmetric frequencies of CuO and ZrO was observed at 1122cm-1

and 1103cm-1[18,19]. Cu-O bond vibrational frequencies appears at 603cm-1

and 656cm-1

. Cu 2+

-

O2-

stretch mode peak appears at around 1336cm-1

[20]. For mixed oxide the combination of both

Cu-O and Zr-O bonds appear in the range 461-988cm-1[Fig1.c]

a b c

Fig 1.a) FTIR Spectrum of(a)nano ZrO2 (b) nano CuO(c) nano CuO-ZrO2 mixed oxide

SEM

Scanning Electron Microscopy (SEM) was used to identify the morphology of the

synthesized metal oxide and mixed metal oxide nanoparticles CuO, ZrO2 and CuO-ZrO2. As shown

in[ Figure 2a and 2b], the prepared CuO and ZrO2 displays granular flakes and mixed granular

appearance. When CuO and ZrO2 were mixed the surface morphologies and roughness of the

particles are changed and some large particles appear [Fig2.c] with uneven hexagonal surface

confirms the formation of mixed CuO-ZrO2. The particle size was also in nanometer range.

Advanced Materials Research Vol. 678 51

a b c

Fig.2. SEM behaviour of (a) nano CuO (b) nano ZrO2 (c) nano CuO-ZrO2 mixed oxide

DSC Analysis

DSC thermogram of CuO, ZrO2 and mixed CuO-ZrO2 are recorded at the heating rate 10o/

min. The glass transition temperature (Tg), crystallization temperature(Tc)and melting point (TM) of

the mixed oxide are determined from the DSC curve [Fig.3.a] shows the melting point(TM) of CuO

at a temperature of 50o

and the Tc value at 5o C. The melting point (TM) of ZrO2 was recorded at a

temperature of 95o,

the Tc value is at 10o C and the Tg value of ZrO2 oxide is -70

o C .[Fig.3.b] The

Tg value of CuO-ZrO2 mixed oxide is -50o C the Tc value is at 20

o C and melted at a temperature of

116o C. [Fig.3.c] According to DSC the melting temperature TM of mixed oxide was increased

remarkably than the simple oxides.

a b c

Fig.3. DSC Thermogram of(a)nano CuO(b) nano ZrO2 (c)nano CuO-ZrO2 mixed oxide

XRD

The metal oxides and mixed oxide synthesized are characterized by XRD. The crystallite

sizes were estimated using Debye-Scherrer equation using full-width at half maximum (FWHM).

The main peaks of CuO appear [Fig4.b] at 2θ = 35.1°, 38.3°, 48.4° 61.2°, 74.7°,and the average

grain size of nano CuO is found to be 25 nm The main peak of ZrO2 appears [Fig4.a]at

2θ=30.478oand the grain size of nano ZrO2 are found to be 10nm.The main peak of nano CuO-ZrO2

appear [Fig4.c] at 2θ =39.714 οand the grain size of nano mixed CuO-ZrO2 is found to be 24 nm

a b

52 Advances in Nanoscience and Nanotechnology

C

Fig4.a) XRD Patterns of(a) nano ZrO2 (b) nano CuO(c) nano CuO-ZrO2 mixed oxide

Cyclic voltammetry

Cyclic voltammetric behaviour of CuO showed two anodic peaks (Fig 5(a)) at 0 .092V and

0.278V which are due to the presence of Cu2O and CuO respectively. The peak obtained at 0.278V

was very nearer to the standard emf of Cu. The CuO and Cu2O are reduced at -0.211V. Cyclic

Voltammetric behaviour of ZrO2 showed one oxidation peak [Fig.5b])observed at 0.179V which

indicated the formation of ZrO2 whereas for mixed oxide two oxidation peaks at 0.072Vand 0.198V

[Fig.5c] were observed which were entirely different from the behaviour obtained for CuO and

ZrO2 confirmed the formation of mixed nano CuO-ZrO2 oxide.

The plot of peak current versus different scan rate for nano CuO-ZrO2 mixed oxide gave a

straight line [Fig 5.d] indicating a good adherent behaviour on electrode surface. Thus

it may act as corrosive agent for paints.

Fig5. Cyclic voltammogram of a) nano CuO b) nano ZrO2 c) nano CuO- ZrO2 mixed oxide

Advanced Materials Research Vol. 678 53

v

Fig.5.(d) Plot of peak current Vs Scan rate for mixed oxide

TGA/DTA Analysis

The weight loss patterns in the thermogravimetric curves of CuO, ZrO2 and mixed oxide

were shown in[figures6(a),6(b)and,6(c)].The first weight loss step from 30oC

to 100

oC [

Fig

6.a]corresponds to loss of moisture .The next step from 101 to170 oC was due to the presence of

extra bounded water molecules .The final weight loss step from 170 oC onwards corresponds to the

degradation of ZrO2.The DTA analysis also exhibited the same behaviour.[Figure6.b]showed the

TGA/DTA behaviour of CuO. In this curve the first weight loss step from 36-100 oC corresponds

to loss of moisture. The next step from 101-300oC was due to the presence of extra bounded water

molecules. The final weight loss step from 301 o

C onwards corresponds to the degradation of

CuO[Fig.6.c] showed the TGA/DTA curve of mixed oxide. In this curve the first weight loss step

from 35o-120

o corresponds to the moisture. The next weight loss step from 121-170

oC corresponds

to extra bounded water molecules. The final weight loss step from 170-914 o

C corresponds to the

degradation of mixed oxide.

a B c

Fig.6. TGA/DTA curves of(a) of ZrO2( b) CuO (c) CuO-ZrO2 mixed oxide

Conclusion

In summary nano CuO,ZrO2 and CuO-ZrO2 were synthesized by wet chemical method. the

size of the synthesized oxides were in the nm range and they withstand thermal stability as they can

possess high surface area. The mixed oxide has good adherent and electrochemical activity and thus

it can be used as corrosive protection agent for paints formulation. The mixed oxides have more

adsorbent properties than the simple oxides.ZrO2 based oxides were good ceramics and utilized in

future nano electronic devices. CuO based mixed oxides were used as semiconductors.

54 Advances in Nanoscience and Nanotechnology

Acknowledgements

The authors are extremely grateful to DST (FAST TRACK and FIST) New Delhi, INDIA

for using CHI Electrochemical workstation and Jasco UV-VIS Spectrophotometer.

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