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Original Research Article

Iranian Chemical Communication Payame Noor University

http://icc.journals.pnu.ac.ir

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium

oxide

nanocomposite

by

the

gel

combustion method and application as catalyst for hydrogen revolution Hassan Karamia,b,*, Mohammad Ali Karimib,c, Ehsan Atinc aNano

Research Laboratory (NRL), Payame Noor University (PNU), P.O. BOX 97, Abhar, Iran

bDepartment

of Chemistry, Payame Noor University, 19395-4697, Tehran, Iran

cNanoscience

and Nanotechnology Research Laboratory (NNRL), Department of Chemistry,

Payame Noor University (PNU), Sirjan, Iran Received: 19 September 2015, Accepted: 29 February 2016, Published: 29 February 2016

Abstract This paper presents a new gel combustion method to synthesize palladium nanoparticles, palladium oxide (PdO) nanoparticles and palladium-palladium oxide nanocomposites. In the proposed method, there are some effective parameters including palladium chloride concentration, polyvinyl alcohol (PVA) concentration, acid concentration, solvent composition and combustion temperature that their values are investigated and optimized by the "one at a time" method. The experimental data shows that the combustion temperature is the main factor that controls the sample composition to obtain palladium, palladium oxide or palladium-palladium nanocomposites. Characterization of the synthesized samples is performed by SEM, TEM, XRD and BET specific surface area measurements. The optimized sample consisted of clusters; each cluster is composed of smaller nanoparticles with an average diameter of 25 mm and 10 m2. g-1 specific surface areas. The optimized PdPdO nanocomposite is successfully used as nanocatalyst for the hydrogen revolution. Keywords: Palladium nanoparticles; palladium oxide nanoparticles; palladiumpalladium oxide nanocomposite; gel combustion; catalyst; hydrogen revolution. *Corresponding author: Hassan Karami Tel: +98 (912) 5419727, Fax: +98 (242) 5226932 E-mail: [email protected]

Iran. Chem. Commun. 4 (2016) …-… Page | 142

H. Karami et al. / Iranian Chemical Communication 4 (2016) …-…

As a gas-sensing agent, palladium

Introduction Great interest has been focused on the

(Pd) has an interesting characteristic of

noble metal nanoparticles due to their

hydrogen molecules, including the large

interesting size- and shape dependent

capacity of hydrogen occlusion and the

physical and chemical properties. They

catalytic effect of the reaction between

are technologically important in many

hydrogen

fields such as catalysis [1,2], optics [3]

temperature. The Pd characteristics are

and

Raman

very attractive for the hydrogen sensor

spectroscopy [4,5]. Among metals,

for which the sensitivities are enhanced

palladium is widely studied because of

by down-sizing into the nanometer

its optical, spectroscopic, magnetic and

range [10]. Therefore, preparation of

catalytic properties. The development

nano-structured Pd is also an active

of the new methods for the preparation

research field [11-13].

surface

enhanced

and

oxygen

at

room

of uniform palladium nanoparticles

Several synthetic approaches and

becomes a very important issue in

different palladium precursors have

heterogeneous catalysis and hydrogen

been applied to generate palladium

storage materials. Palladium has an

nanoparticles having different shapes

important role in chemical synthesis [6]

and sizes such as chemical reduction of

and

industrial

PdCl2 by NaBH4 [14], arc-discharge

of

[15],

in

many

applications[7,8].

Major

Pd

reduction

of

supercritical

fine Pd particles where both the size

thermally

and shape are critical parameters that

Pd(Fod)2

should be controlled in order to

reduction of PdCl2 [18]. The size and

maximize

For

shape of palladium nanoparticles have

example, the reactivity and selectivity

been discussed as a function of metal

of a nanocatalyst can be tailored by

precursor concentration and of the

controlling the

will

effect of the surfactant molecules.

determine the crystallographic facets

However, the aqueous-phase synthesis

exposed on the surface of a nanocrystal

of

and therefore the number of atoms

environmentally-friendly process is still

located at the edges or corners [9].

challenging.

efficiencies.

shape, as

it

Page | 142

induced [17]

uniform

and

dioxide

in

applications requires very small and

their

carbon

Pd(OAc)2 reduction

[16], of

sonochemical

nanoparticles

by

an

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium …

Palladium

oxide

is

the

most

Instrumentals

important catalyst that is used for

Morphologies of the samples were

various reactions in the laboratory and

characterized by scanning electron

industry. It has been used for catalytic

microscopy (Model XL-30, Philips,

oxidation of benzyl alcohol [19],

Netherland).

sensing of OH radicals [20], oxidation

microscope (Zeiss EM900, 80Kev) was

of hydrocarbons [21], photocatalytic

used for determining the exact size and

degradation of bacterial indicators, etc.

shape of particles. The composition and

[22].

particles sizes of the samples were

Transmission

electron

There are many reports about the

determined by XRD (E- Pert- MPD,

synthesis of Palladium nanocomposites

Phillips, Netherland). The effective

such

palladium-polyaniline

surface areas were determined by

nanocomposite [23, 24], palladium-

Brunauer-Emmet-Teller (BET) specific

polycarbonate

surface area measurements based on N2

[26],

as

[25],

palladium-silica

palladium-polypyrole

palladium-carbon

nanotube

palladium-hematite

[29],

[27],

adsorption/desorption (Temcem 902 A

[28],

Z Picc, Germany).

palladium-

Procedure

alumina [30], etc. The large number of

Appropriate

reports

palladium

palladium chloride was dissolved in a

their

mixed solvent ethanol: HCl (0.1 M)

about

nanocomposites

reveals

weight

percent

of

importance in catalysts and sensors.

(60:40). Then 8 g polyvinyl alcohol

In this work, we present a new

(PVA) was added into the obtained

controllable method to synthesize Pd

solution. The mixture was stirred until a

nanoparticles, PdO nanoparticles and

transparent and homogeneous solution

Pd-PdO nanocomposites.

was obtained which called "sol".

Experimental

During

Materials and reagents

temperature should be kept lower than

All reagents and compounds were in

80 ºC. After sol formation, the mixture

analytical grade and obtained from

was

Merck, Fluka and Loba Chimie (India).

homogeneous gel. The obtained gel was

Double-distilled water was used in all

heated until the complete solvent

experiments.

evaporation and the formation of a

Page | 143

sol

slowly

formation,

heated

to

solution

form

a

H. Karami et al. / Iranian Chemical Communication 4 (2016) …-…

dried gel. The dried gel was pyrrolized

optimization

at 500 ºC for 5 h. At this stage,

presented.

aluminum

Effect of gel making value

and

zinc

salts

were

experimental

set

is

decomposed and converted to metal

Polyvinyl alcohol (PVA), generally

oxides. Aluminum oxide and zinc oxide

used as suspension stabilizer, exhibits

were

a

the effect of reducing particle size of

obtained

the sample by decreasing the surface

connected

nanocomposite.

to

form

The

nanocomposites

were

studied

by

tension and by improving the dispersion

scanning electron microscopy (SEM),

of

transmission

microscopy

polymerization reaction [31]. Polyvinyl

(TEM), EDAX analysis, XRD patterns

alcohol (PVA) is a hydrophilic polymer

and

(BET)

contributing hydroxyl group on each of

specific surface area measurements.

its repeating units, which permits the

SEM and TEM instruments were used

development of hydrogen bonds with

to define the morphology of the

the hydroxyl and carboxyl groups of

samples. XRD, TEM, SEM and BET

reactants

were used for determining particles

sedimentation

sizes. The compositions of the samples

particles to trammel in gel pores while

were measured by XRD and EDX

the solvent evaporates silently and thus,

analyses.

not

Results and discussion

combustion method, the gel network

In the present method, there are some

rigidity controls the morphology and

effective parameters which can control

the particle sizes of the synthesized

the morphology, the particle sizes and

sample

the composition of the synthesized

nanostructured [33, 34]. In the gel

samples. The parameters include gel-

structure, palladium chloride molecules

making

solvent

were homogeneously dispersed through

composition, pH, palladium salt value,

the polymeric network. Because of gel

and combustion temperature. The effect

network

of each parameter was investigated and

molecules in the gel network cannot

optimized by the one factor at a time

alter their positions. Therefore, during

method. In the following sections, the

the combustion of the gel’s layers, the

electron

Brunauer-Emmet-Teller

value,

mixed

Page | 144

the

reactants

[32].

impacting

to

during

the

PVA

prolongs

reaction,

causing

again.

make

rigidity,

In

a

the

the

gel

uniform

dispersed

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium …

palladium chloride molecules of the

agent (PVA) has not any effect on the

burnt layers combine with each other to

sample

create PdCl2 particles. The formed

temperature, all samples were in Pd-

particles are calcined to yield Pd, PdO

PdO nanocomposite form, including 50

or Pd-PdO nanocomposites during the

wt% Pd and 50 %wt PdO. The PVA

pyrrolysis

these

amount affects on the morphology and

were

particle sizes of the samples. Figure 1

paralyzed at a constant combustion

shows the SEM images of the samples

temperature (500 °C). XRD patterns

that were synthesized by different

showed that the amount of gel- making

content of PVA.

process.

experiments,

all

In samples

composition.

In

this

Figure 1. SEM images of Pd/PdO nanocomposites synthesized at different initial concentrations of PVA; 0 (a), 4 (b), 6 (c), 8 (d), 10 (e) and 12 %wt (f).

As it is visible in Figure 1, the PVA content

changes

considerably

complete and suitable to control the

the

mechanism and kinetics of Pd-PdO

morphology and particle sizes of the

nanocomposite particles. At lower PVA

samples. The compact nanoparticles in

content, the gel network is not rigid

the absence of PVA is converted to

enough. Because of the low solubility of

nanoporous rice shape clusters. The gel

PVA in ethanol-HCl solution, at higher

network is completed when the PVA

content (12 %wt, Figure 1f); it is not

content is increased from 0 to 10 %wt.

obtained a uniform gel. Therefore, the

At 10 %wt PVA, the gel network is

Page | 145

H. Karami et al. / Iranian Chemical Communication 4 (2016) …-…

sample

doesn’t

have

uniform

solubility of palladium chloride is low

morphology.

in ethanol-HCl mixed solution.

Effect of initial palladium salt content

Solvent composition

on the morphology and particle sizes

Based on our previous experiences [33],

It is expected that the content of

ethanol-water is a suitable solvent to

palladium

have

make PVA sol and PVA gel for

considerable effects on the morphology

synthesizing metal oxide nanoparticles.

and

Initial

chloride

particle

sizes

will

of

Pd-PdO

experiments

showed

that

nanocomposites. For evaluation of this

palladium chloride does not have

parameter, there was an attempt to

enough

synthesize some sample at different

According to chemistry facts, palladium

amounts of palladium chloride. Figure 2

chloride only has enough solubility in

shows the SEM images of the samples

acidic media. Therefore, we used HCl

that were synthesized at 1, 2 and 3 %wt

solution mixed with ethanol as suitable

palladium chloride.

solvent that both PVA and palladium

solubility

in

this

solvent.

At the contents lower than 1 %wt,

chloride have enough solubility to make

the amount of the final sample with

a uniform sol and consequently a

respect to initial sol volume is very low

uniform gel.

so the sample weight is not enough for

Figure 3 shows the effect of

collecting and analysis. In addition, as

different concentrations of HCl on the

Figure 2 shows, at low (1 %wt) and

morphology of the samples. At low

high (3 %wt) concentrations, the sample

concentration, palladium chloride does

does not have uniform morphology. At

not have enough solubility. At 0.1 M

high concentration (3 %wt), there are

HCl, the sample includes uniform

two reasons for decreasing of sample

nanoclusters

homogeneity.

nanoseeds.

made

from

uniform

At higher concentrations,

Firstly, the ratio of salt to PVA is

the hydroxyl groups in PVA chains are

high, causing the gel network to be too

protonated. The protonated PVA cannot

weak to control the pyrrolysis and

make a polymeric gel to control the

calcination processes. Secondly, the

synthesis process.

Page | 143

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium …

Figure 2. Effect of palladium chloride weight percentage (%wt) on the morphology and the particles sizes of the samples. The SEM images of samples with different palladium salt percentages of 1 %wt (a), 2 %wt (b) and 3 %wt (c).

Page | 143

H. Karami et al. / Iranian Chemical Communication 4 (2016) …-…

Figure 3. SEM images of different samples synthesized at different concentrations of hydrochloric acid; 0.05 M (a), 0.1 M (b), 0.5 M (c), 1 M (d) and 2 M (e). All SEM images are in same magnifications of 15000.

In the next step, the effect of

compositions of mixed solvents. The

ethanol/HCl solution ratio in a mixed

effect of solvent composition was

solvent

shown in Figure 4 using SEM images.

was

investigated.

Several

samples were synthesized at different

Page | 144

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium …

Figure 4. Effect of solvent composition on the SEM images of nanocomposite samples synthesized at 60:40 ethanol: HCl solution (a), 70:30 ethanol: HCl solution (b) and 80:20 ethanol: HCl solution (c) as solvent in the synthesis process.

The experimental results showed

solvent with 60 %V/V ethanol and 40

that in ethanol content lower than 60

%V/V HCl solution is a suitable solvent

%V/V, PVA has no solubility. At

to synthesize uniform nanoclusters.

higher

Effect of pyrrolysis temperature

values,

palladium

chloride

cannot completely dissolve. Based on

In the present method, during the

the SEM images of Figure 4, the mixed

pyrrolysis

Page | 142

(combustion)

process,

H. Karami et al. / Iranian Chemical Communication 4 (2016) …-…

organic gel network is burnt and the

5a and 5b), the clusters are compact and

trapped palladium chloride molecules in

they don't have enough porosity. At

holes in the polymeric network are

these temperatures, calcination and

calcinated

and

into

particle growth rates are low because

palladium,

palladium

or

the combustion rate is low resulting in

oxide

smaller particles of the samples. But, at

chemical

lower temperature, the samples don’t

converted oxide

palladium-palladium nanocomposites.

The

reactions of the combustion step are as

have uniform nanoclusters.

follows:

At higher temperatures (550 and 600 °C; Figs. 5d and 5e), it can be seen that

Heat

(eq. 1)

PdCl2  Pd  Cl 2 

the samples consist large crystals. The

Heat

(eq. 2) 2 PdCl2  O2  2 PdO  2Cl 2 

presence of large crystals can be related

(eq.

to this fact that the combustion,

3)

(m  n) PdCl 2 

1 O2  mPd .nPdO  2Cl 2  2 Heat

The pyrrolysis temperature controls the share of each reaction (eqs. 1 to 3) in the final product. In equation 3, m and n can be varied as the synthesis

the

temperature

effect was

high. Therefore, the samples that are synthesized

in

these

temperatures

include agglomerated particles and large crystals. At 500 °C, combustion, calcination, nucleation and particle growth rates are suitable to form

temperature is changed. First,

calcination and particle growth rates are

of

studied

pyrrolysis on

the

morphology of samples (Figure 5). As it can be seen in Figure 5, the morphology of the samples is changed considerably when the pyrrolysis temperature is increased from 400 to 600 °C. At lower

uniform nanoclusters (Figure 5c). Gel network is a control cage for palladium chloride molecules. When a gel is burned, burning rate is a limiting factor for the calcination rate of the salts and also a controller factor to reduce nucleation and particle growth [33].

temperatures (400 and 450 °C; Figures

Page | 143

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium …

Figure 5. SEM images of the samples synthesized at different paralysis temperatures, including 400 °C (a), 450 °C (b), 500 °C (c), 550 °C (d) and 600 °C (e).

Figure 6 shows the TEM images of the sample synthesized at 500 °C. As it can be seen in Figure 6, the sample includes uniform and spherical nanoparticles with an average diameter of 25 nm.

Figure 6. TEM images of Pd/PdO nanocomposite sample synthesized in the optimized conditions in two magnifications 20000 (left) and 70000 (right).

Page | 142

H. Karami et al. / Iranian Chemical Communication 4 (2016) …-…

In the next step, the effect of

synthesized at different temperatures.

pyrrolysis temperature was studied on

As Figure 8 shows, Pd content of the

the sample composition. Seven samples

samples decreases when the pyrrolysis

were

different

temperature is increased. At 350 °C, Pd

temperatures under free atmosphere.

content of the sample is more than 98

The composition of the samples was

%wt and, at 700 °C, the Pd content is

characterized by XRD patterns. Figure

lower than 2 %wt. Based on the

7 shows the XRD patterns of three

obtained results, the presented method

samples (as some examples) that were

is a powerful technique to synthesize Pd

synthesized at 400, 500 and 600 °C. As

nanoparticles, PdO nanoparticles and

it can be seen in Figure 7, Pd content of

Pd-PdO nanocomposites. By comparing

the

the

the morphology, particles sizes and the

pyrrolysis temperature is increased. The

composition of the samples that are

reason of this fact is clear. Under free

synthesized

atmosphere conditions, Pd reacts with

temperatures, it can be concluded that

oxygen to produce PdO. At lower

the introduced method is more suitable

temperatures, the oxidation reaction is

for

negligible. On the other hand, PVA can

nanocomposites.

synthesized

sample

at

decreases

when

act as a reducing agent to convert Pd

2+

0

into Pd .

different

preparation

of

pyrrolysis

Pd-PdO

In the optimum conditions, the Pd/PdO nanocomposite sample includes

Figure 8 was drawn based on the XRD

at

patterns

of

the

samples

uniform nanoclusters with uniform nanoseeds.

Page | 142

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium …

Figure 7. XRD patterns for the three Pd/PdO nanocomposite samples pyrrolized at different temperatures of 400, 500 and 600 ºC

Brunauer- Emmet- Teller (BET)

Application as catalyst

specific surface area measurements

The catalytic performance of the

were used for the determination of the

palladium-palladium

pore volume, the specific surface area

nanocomposite (50 %wt Pd and 50 %wt

and the nanoparticles sizes. Based on

PdO)

the BET and BJH plots which were

Voltammetry

obtained

gas

hydrogen in acidic solution. For this

adsorption/desorption isotherms, the

purpose, commercial palladium powder

based 2

on -1

sample has 10 m .g

N2

specific surface

area and 19.5 nm average diameter.

pore

was

studied for

oxide

by

Cyclic

revolution

of

and the prepared palladium-palladium oxide nanocomposite were filled in the porosities of the graphite electrodes.

Page | 143

H. Karami et al. / Iranian Chemical Communication 4 (2016) …-…

The obtained electrodes were used as

palladium-palladium

working

cyclic

nanocomposite were compared with

The

those of graphite and commercial

electrodes

Voltammetry

in

experiments.

obtained cyclic voltammetric results for

oxide

palldium.

Figure 8. Effect of pyrrolysis temperature on the sample composition. Any of the samples does not have any impurity.

Figure

9

shows

cyclic

obtained

results

for

the

catalytic

voltammograms of hydrogen reduction

performance of Pd/PdO nanocomposite,

in sulfuric acid solution (1 M) on the

the prepared nanocomposite can be

different substrates (pure

used as catalyst in fuel cells to facilitate

graphite,

commercial palladium intercalated in

and

graphite porosities and the synthesized

hydrogen reactions

palladium-palladium

increase

current

densities

of

oxide

An interesting phenomenon is

nanocomposite intercalated in graphite

considered on CV diagram taken by

porosities). As it can be seen in Figure

palladium-palladium

9,

oxide

nanocomposite substrate; an oxidation

reduces

peak was observed at 0.14 V versus

palladium-palladium

nanocomposite

not

only

oxide

reduction potential of hydrogen ions

Ag/AgCl

reference

(positive shift), but also increases

Commercial

palladium

hydrogen revolution rate with respect to

graphite substrates did not show this

commercial palladium. Based on the

peak. The observed peak is related to

Page | 143

electrode. and

also

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium …

oxidation of the adsorbed hydrogen gas.

At oxidation sweep (from -0.3 to 0.3

This peak reveals that palladium-

V), the adsorbed hydrogen gas is

palladium oxide nanocomposite has

oxidized to hydrogen ion. There is not

more capacity to adsorb hydrogen gas.

any adsorption of realized hydrogen on

Hydrogen ions are reduced during

the surface of graphite and commercial

potential sweeping from 0.0 to -0.85 V.

palladium or it is very weak. The strong

The realized hydrogen was strongly

adsorption of hydrogen gas on the

adsorbed by palladium-palladium oxide

surface of the nanocomposite helps to

nanocomposite.

improve its catalytic performance.

Figure 9. Cyclic voltammograms for hydrogen revolution in 1 M sulfuric acid on the surface of palladium-palladium nanocomposite (a), commercial palladium power and pure graphite (c). All potential were recorded versus Ag/AgCl reference electrode. Commercial palladium and palladium-palladium nanocomposite powders were intercalated (filled) on the graphite pores. The filled graphite electrodes were used as working electrodes.

Conclusion

synthesized with the more specific

A gel combustion method based on

surface area. They were expected to

PVA as a gel-masking agent can be

have some improved ability in gas

used

sensing and photocatalytic applications.

as

synthesize

a

powerful PdO,

Pd

method and

to their

nanocomposites. In this procedure, Pd,

Palladium

nanoparticles

can

be

successfully used as nanocatalyst to

PdO and their nanocomposites were

Page | 143

H. Karami et al. / Iranian Chemical Communication 4 (2016) …-…

catalyze hydrogen generation in acid

[9] A. Kolmakov, D.O. Klenov, Y.

media.

Lilach, S. Stemmer, M. Moskovits,

Acknowledgments

Nano Lett. 2005, 5, 667-673.

We gratefully acknowledge the support

[10] J. Chen, B. Wiley, J. McLellan, Y.

of this research by Payame Noor

Xiong, Z. Li, Y. Xia, Nano Lett. 2005,

University Research Council.

5, 2058-2062.

References

[11] Y. Sekiguchi, Y. Hayashi, H.

[1] R.M. Rioux, H. Song, M. Grass, S.

Takizawa, Mater. T. JIM., 2011, 52,

Habas, K. Niesz, J.D. Hoefelmeyer P.

1048-1052.

Yang, G.A. Somorjai, Top. Catal.,

[12] J. Cookson, Platinum metals Rev.,

2006, 39, 167-173.

2012, 56, 83-98.

[2] A.L. Stepanov, A.N. Golubev, S.I.

[13] T. Tsuji, K. Iryo, H. Ohta, Y.

Nikitin, Y.N. Osin, Rev. Adv. Mater.

Nishimura, Jpn. J. Appl. Phys., 2000,

Sci., 2014, 38, 160-175.

39, 981-983.

[3] Y. Seol, A.E. Carpenter, T.T.

[14] N.R. Jana, Z.L. Wang, T. Pal,

Perkins, Opt. Lett. 2006, 31, 2429-

Langmuir, 2000, 16, 2457-2463.

2431.

[15]

[4] Z.Q. Tian, B. Ren, D.Y. Wu, J.

McCutchen, A. Kruize, H. Heinrich, M.

Phys. Chem. B, 2002, 106, 9463-9483.

Meyyappan, S. Seal, Chem. Phys. Lett.,

[5] S.W. Han, K.Y. Lee, Korean Chem.

2004, 386, 364-368.

Soc. 2005, 26, 1427-1430.

[16] A. Kameo, T. Yoshimura, K.

[6] B. Woodward, Platinum Metals

Esumi, Colloid Surf. A, 2003, 215, 181-

Rev., 2012, 56, 213-217.

189.

Y. Nishihata, J. Mizuki, T. Akao, H.

[17]

Tanaka, M. Uenishi, M. Kimura, T.

Nanotechnology, 2004, 15, 1059-1064.

Okamoto, N. Hamada, Nature, 2002,

[18] K. Okitsu, H. Bandow, Y. Maeda,

418, 164-167.

Chem. Mater., 1996, 8, 315-317.

[7] C.P.K. Rao, D.C. Trivedi, Coordin.

[19] K. Wada, K. Yano, T. Kondo, T.A.

Chem. Rev., 2005, 249, 613-631.

Mitsudo, Catalysis Today, 2006, 117,

[8] Y. Sun, Z. Tao, J. Chen, T.

242-247.

Herricks, Y. Xia, J. Am. Chem. Soc.

[20] J. Liu, G. Lagger, P. Tacchini, H.

2004, 126, 5940-5941.

Girault, J. Electroanal. Chem.,

Page | 143

D.

Bera,

P.F.

S.C.

Ho,

Kuiry,

K.M.

M.

Chi,

Synthesis of nanostructured palladium, palladium oxide and palladium-palladium …

2008, 131, 619-620.

[27] L. Hong, Y. Li, M. Yang, Sens.

[21] G. Postole, B. Bonnetot, A.

Actuators B, 2010, 145, 25-31.

Gervasini, C. Guimon, A. Auroux, N.I.

[28] Z. Li, J. Li, X. Wu, S. Shuang, C.

Lonescu, M. Caldararu, Appl. Catalysis

Dong, M.M. Choi, Sens. Actuators B,

A, 2007, 316, 250-258.

2009, 139, 453-461.

[22] P. Wu, R. Xie, J.A. Imlay, J.K.

[29] H. Liu, M. Liang, C. Xiao, N.

Shang,

Zheng, X. Feng, Y. Liu, J. Xie, Y.

Appl. Catalyst B, 2009, 88,

576-581.

Wang, J. Molec. Catalysis A, 2009,

[23] A.A. Athawalie, S.V. Bhaghwat,

308, 79-86.

B.B. Katre, Sens. Actuators B, 2006,

[30] A.L. Ahmed, N.N.N. Mustafa, Int.

114, 263-267.

J. Hydr. Ener. 2007, 32, 2010-2021.

[24] S. Ivanov, U. Lange, V. Tsakova,

[31] J.S. Kim, C. Han, J.H. Wee,

V.M. Virsky, Sens. Actuators B, 2010,

Talanta, 2006, 68, 963-968.

150, 271-278.

[32] P. Fatehi, H. Xiao, Colloids Surf.

[25]

O.P.

Ostroverkhova,

Valmikanathan, I.S.

Mulla,

O.

A: Physicochem. Eng. Aspects, 2008,

K.

327, 127-133.

Vijayamohanan, S.V. Atre, Polymer,

[33] H. Karami, A. Aminifar, H.

2008, 49, 3413-3418.

Tavallali, Z. Namdar, J. Clust. Sci.

[26] Elvan Sari, Manhoe Kim, Steven

2010, 21, 1-9.

O. Salley, K.Y. Simon Ng, Appl.

[34] H. Karami, Int. J. Electrochem.

Catalysis A, 2013, 467, 261-269.

Sci. 2010, 5, 720-730.

Page | 144