Decoration of silver nanoparticles on activated graphite substrate and their electrocatalytic activity for methanol oxidation

The electrochemical studies of Graphite, Sn/Graphite and successive decoration of AgeSn/Graphite powder have been carried out using cyclic voltammetry in the potential range between 1.2[r]

Trang 1

Original Article

Decoration of silver nanoparticles on activated graphite substrate and

their electrocatalytic activity for methanol oxidation

M.S Shivakumara, G Krishnamurthyb,**, C.R Ravikumarc,*, Aarti S Bhattd

a Research Centre, Dept of Chemistry, ACS College of Engineering, Bangalore, 560074, India

b DOS in Chemistry, Bangalore University, Bangalore, 560001, India

c Dept of Chemistry, East West Institute of Technology, Bangalore, 560091, India

d Department of Chemistry, NMAM Institute of Technology, Nitte, 574110, India

a r t i c l e i n f o

Article history:

Received 21 December 2018

Received in revised form

31 May 2019

Accepted 3 June 2019

Available online 10 June 2019

Keywords:

Silver nanoparticles

Electro catalyst

Graphite powder

Electroless deposition

Methanol oxidation

a b s t r a c t

Silver nanoparticles (~30e70 nm) have been impregnated on the activated graphite powder by an electroless plating method The so prepared silver decorated graphite powders are characterized byﬁeld emission scanning electron microscopy, powder X-ray diffraction, energy dispersive X-ray and X-ray photoelectron spectroscopy The activated graphite powder displays a high surface coverage with tin which is essential, as this ensures a thorough and complete coating of the graphite powder with silver The electrochemical studies of Graphite, Sn/Graphite and successive decoration of AgeSn/Graphite powder have been carried out using cyclic voltammetry in the potential range between1.2 and 0.0 V at

a sweep rate of 50 mV s1and their electrocatalytic activity for methanol oxidation has been examined in alkaline medium The effective active surface area of Graphite and AgeSn/Graphite electrode are calculated to be 6.2479 105cm2and 6.7886 105cm2, respectively The impedance spectrum of the AgeSn/Graphite electrode displays a depressed semicircle in the high-frequency region which corre-sponds to low charge resistance and high capacitance The results highlight the electrocatalytic behavior

of the graphite supported silver nanoparticles, making them suitable for fuel cell applications

© 2019 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

1 Introduction

Electroless deposition of silver nanoparticles on various

sub-strates is a well-known technique, which generally employed for

this metal This method involves pretreatment of the substrate

surface, sensitization and activation for increasing the rate of

metal ions reduction on the surface of carbon substrate [1e3]

The applications of silver nanoparticles (Ag NPs) thus obtained

according to their properties like electric conductivity, re

ﬂec-tivity and other surface properties such as their ability to absorb

as well as chemisorb, making them suitable candidates for

catalysis applications [4e8] These properties also lend them

unique biological, chemical and physical properties matching up

to their macro-scaled counterparts No wonder, Ag NPs have also

been used in variedﬁelds such as renewable energies, medicine and environment[9,10]

An alternative for the reduction of silver nanoparticles is to introduce organic functional groups, for instance, carboxyl and hydroxyl groups onto the carbon surface [11,12] These organic functional groups act as binding sites to the metal ions which un-dergo reduction to ultimately form a metal layer on the carbon surface[13,14] Carbon materials such as graphite are widely used

in industries and processing techniques due to their high conduc-tivity and elevated speciﬁc surface area Also, the low cost of graphite adds to its preferences[15]

Electrocatalysts are generally employed in fuel cells as it helps in improving the fuel oxidation However, the high cost of fuel cells and its low durability hinders its wide application In order to make these fuel cells affordable, research is being carried out to decrease the cost by decreasing the amount of expensive elements used or

by substituting some of the expensive components with cheaper but more durable materials Simultaneously, an effort is being made

to improvise its durability by developing high durable catalyst supports or it can also be done by using Pt alloys as electro catalysts [16] Carbon based materials make a better catalyst support; for

* Corresponding author.

** Corresponding author.

E-mail addresses: drgkmurthy.bub@gmail.com (G Krishnamurthy), Ravicr128@

gmail.com (C.R Ravikumar).

Peer review under responsibility of Vietnam National University, Hanoi.

Contents lists available atScienceDirect Journal of Science: Advanced Materials and Devices

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d

https://doi.org/10.1016/j.jsamd.2019.06.001

Journal of Science: Advanced Materials and Devices 4 (2019) 290e298

Trang 2

instance XC-72 Vulcan carbon powder is a widely used support in

the electrodes of several modern fuel cells The graphite submicron

particles on the catalyst support aids in the oxidation of fuel cells

application

Our present work employs the electroless plating method to

reduce silver nanoparticles by introducing organic functional

groups on the activated graphite powder with electrocatalytic

surfaces This serves as a better platform to obtain decorated silver

nanoparticles on sensitized and activated graphite powders The

oxidized graphite powders have been treated with reducing agent

and immersed in Ag bath solution (pH 11) to obtain silver

nano-particles on graphite powders [17] The so-prepared decorated

silver nanoparticles on sensitized and activated graphite have been

tested for their electrocatalytic activity of methanol oxidation in

alkaline solution by cyclic voltammetry (CV) and electrochemical

impedance spectroscopy (EIS) The surface morphology, structure,

composition have been characterized by Field emission scanning

electron microscopy (FESEM), Energy dispersive X-ray analysis

(EDX), powder X-ray diffraction (PXRD) and X-Ray photoelectron

spectroscopy (XPES)

2 Materials and methods

All the chemicals have been procured from SigmaeAldrich and

have been used without any further puriﬁcation Graphite powder,

silver nitrate, stannous chloride, polyethylene glycol, glucose,

po-tassium hydroxide and methanol used have99.99% purity The

solvents sulphuric acid, nitric acid and aqueous ammonium

hy-droxide solution are of AR grade

2.1 Functionalization of graphite powder

About 1 g of graphite powder was treated in 200 cm3of an acid

mixture of conc HNO3and conc H2SO4(1:3 v/v) and reﬂuxed at

110C for 8 h to produceeOH and eCOOH functionalized graphite

powder The samples were then ﬁltered, washed with distilled

water and dried at 95± 3C for about 6 h Thus, the functionalized

graphite powder was obtained

2.2 Decoration of silver nanoparticles on graphite powder

To obtain decorated silver nanoparticles on graphite by

elec-troless plating, 2 g of oxidized graphite powder (<20mm) was

treated with 50 cm3 of 20% SnCl2, stirred for 10 min and then

ﬁltered The obtained graphite powder was then treated with

30 cm3of glucose solution, 20 cm3of methanol and 1 g of

poly-ethylene glycol, stirred for 10 min, ﬁltered and transferred to a

250 cm3of silver bath solution (3 g of AgNO3in 250 cm3of water)

along with 0.6 g NaOH To this, ammonia solution was added

dropwise to get a clear solution, stirred for 45 min,ﬁltered and

dried[17]

2.3 Characterization

The samples were characterized by powder X-ray diffraction

studies using a high-resolution X-ray diffractometer (Shimadzu

7000S) at a scanning rate of 2 min1using CuKaradiation It was

operated at 45 kV and 40 mA The surface morphology of the metal

coating and the extent of coverage were analyzed using a Carl Zeiss Ultra 55 FESEM The elemental analysis was done using Axis Ultra X-Ray Photoelectron spectroscopy The electrochemical studies were carried out using an Auto lab PGSTAT30 model with pilot integration controlled by GPES 4.9 software in a three-compartment cell The measurements were carried in the fre-quency range of 1 Hz to 1 MHz The experimentally obtained real and imaginary components were analyzed using the CH608E instrument

2.4 Preparation of working electrode For the preparation of carbon paste electrode, 500 mg of silver decorated graphite powder was thoroughly mixed with 20% of silicone oil The resulting paste was packed into a Teﬂon tube and a copper wire was inserted for external electric contact The surface was polished by butter paper When necessary, a fresh surface was obtained by pushing an excess and polishing the electrode surface mechanically using steel rod

3 Results and discussion 3.1 The mechanism of Ag deposition on Sn/graphite The mechanism of deposition of silver on graphite substrate involves,ﬁrstly, the sensitization of graphite surface in the SnCl2

solution to enhance the absorption of silver ions in the subsequent activation process The stannous ions adsorbed on to the surface of functionalized graphite surface during sensitization act as seeds for the nuclei of the Ag nanoparticles growth during activation process The initial formation of the silver nanoparticles is based on the application of reducing and oxidizing agents on the graphite sub-strate surface, namely Sn2þand Agþ This redox reaction proceeds as [8,18e20]

In this method, which is a form of polyol method, ethylene glycol acts as a reducing agent Silver nanoparticles are synthesized during the reduction of silver ions while the hydroxyl groups of poly (ethylene glycol) are oxidized to aldehyde groups

2AgNO3 þ 2NaOH /Ag2OðsÞ þ 2NaNO3þ H2O (2)

HOCH2CH2OH/ CH3CHOþ H2O (4)

CH3CHOðaqÞ þ 3OH/CH3CHOOþ 2H2O þ 2e (5)

2AgðNH3Þ2NO3ðaqÞ þ CH3CHO/2Ag0 þ CH3COOHþ 4NH3

þ HNO3

(8)

Ag2OðSÞ þ 4NH3ðaqÞ þ 2NaNO3ðaqÞ þ H2O/2AgðNH3Þ2NO3ðaqÞ þ 2NaOH (7)

M.S Shivakumar et al / Journal of Science: Advanced Materials and Devices 4 (2019) 290e298 291

Trang 3

The above equations (eqs.(2)e(8)) depict the possible proposed

mechanism of the in situ synthesis of silver nanoparticles under alkali

conditions On coming in contact with the alkali solution, silver nitrate

gets converted to anhydrated Agþ; a reaction between OHions with

silver ions leads to the formation of silver oxide (Ag2O) In presence of

a highly alkaline environment (pH 13), Ag2O dissociates into silver

ions bonded to the hydroxyl and carboxylate moieties on the surfaces

of graphite through ionic interactions (eq.(1))

Simultaneously, polyethylene glycol undergoes alkaline

hy-drolysis to produce aldehyde which oxidizes releasing electrons

As a result, silver ions reduce to silver nanoparticles, resulting in

a transparent clear solution (eq.(5)(8)) Similar to silver ions,

the resulting silver nanoparticles also remain bonded onto the

graphite surface Finally, a nano layer of silver nanoparticles is

deposited on the graphite surface by treating it with alkali in

presence of ammonia solution As shown in equation(2), silver

nitrate in presence of alkali oxidizes to silver oxide, leading to

the formation of Agþions Some of the Agþions produced are

reduced to Ag0 whereas the remaining form a diammine silver

(I) complex on addition of ammonia; the complex so formed is

Tollen's reagent Tollen's reagent is a commonly used source to

synthesize silver nanoparticles, as it readily undergoes reduction

to form Ag0 in presence of aldehyde which in turn oxidizes to

carboxyl group Being positively charged, [Ag(NH3)2]þalso gets

easily absorbed onto the graphite surface via eCOO and eOH

functional groups[21e23]

3.2 Powder X-ray diffraction studies

The diffraction pattern of the silver decorated graphite powder

was studied on a PXRD FromFig 1(a) it can be seen that PXRD

patterns of graphite showed very strong peaks at 2qof 26.66and 54.81 which matches very well with that of graphite powder The PXRD also exhibited diffraction peaks at 38.26, 44.23, 64.8, 74.7 and 76.6 corresponding to (111), (200), (220), (222) and (311) planes of silver as well as diffraction peaks at27.7, 32.46,

57 and 67.8 for tin The average crystallite size (D) of nano-particles was estimated from diffraction planes along the direc-tion normal to the (h k l) plane applying Scherrer's formula and was found to be around 34 nm The PXRD peaks further conﬁrmed the crystalline nature of silver nanoparticles[24], this indicates a uniform and good decoration of silver nanoparticles on graphite

3.3 Energy dispersive X-ray analysis EDX analysis was carried out to conﬁrm the deposition of silver

on the graphite layer This is evident fromFig 1(b) which displays the EDX pattern of silver deposited graphite powder Theﬁgure clearly hows prominent peaks corresponding to silver and tin along with the carbon peak

3.4 Field emission scanning electron microscopy The surface morphology of the silver coating and uniformity

in distribution were analyzed by a FESEM.Fig 2shows the im-ages of as obtained silver nanoparticles deposited graphite powder The powder seems to have a rod like structure and the average size of the silver nanoparticles on the surface of acti-vated graphite is approximately in the range between 30 and

70 nm This agrees well with the crystallite size calculated via PXRD in section3.2

Trang 4

3.5 X-ray photoelectron spectroscopy

Fig 3 shows the wide angle spectra for silver deposited on

graphite powder and also the individual binding energy spectrum

of silver, tin and carbon The Ag3d5/2and Ag3d3/2peaks at 367.5 eV

and 373 eV are attributed to silver The peaks at 486.5 eV and

495 eV correspond to tin and the peak at 284.2 eV corresponds to

carbon 1Cs of graphite The characteristic XPES spectrum with

appropriate binding energies and intensities further conﬁrmed the

deposition of silver and tin on graphite[25e27]

3.6 Electrochemical characterization of electrode 3.6.1 Cyclic voltammetry studies

Fig 4(a) represents the CV for the AgeSn/Graphite carbon paste electrode in 0.5M KOH with increasingly varying methanol con-centrations such as 0.025e1 M During the course of the study, the

CV exhibited a signiﬁcant change in its response and also anodic peak current (Ipa) value for methanol oxidation The values are tabulated in Table 1 It can be observed that in the presence of

CH3OH anodic peak current appears at 0.75 V, which is in

Fig 2 FESEM images of silver nanoparticles deposited on Graphite powder: (a) 5000 X and (b) 50,000 X.

0 40000

80000

120000

160000

Binding Energy(eV)

(a)

2000

4000

6000

8000

495.2eV

0 500 1000 1500 2000 2500 3000

Carbon 284.2eV (b)

0 2000 4000 6000 8000

Silver 367.5eV (d)

373.6eV

Trang 5

accordance with the oxidation of CH3OH at crystalline Ag NPs With

an increase in the methanol concentration, the peak response

in-creases initially up to 1M methanol, followed by a decrease in the

peak response It is also noteworthy that above 1 M of methanol

concentration, the oxidation current decreases This is probably due

to the adsorption of methanol molecules on the electrocatalyst leading to the blockage of active sites[28]

If we examine the electrocatalyst performance (Table 2), for all the three systems the onset potential for CH3OH oxidation remains constant However, anodic peak current and anodic peak potential

0.0

Potential (V)

0.025 M CH3OH

1 M CH3OH

Ag-Sn/Graphite electrode

0.0

Potential (V)

Graphite (a) Sn/Graphite (b) Ag-Sn/Graphite (c)

(a) (b)

(c) 1M CH 3 OH + 0.5 M KOH

0.0

Potential (V)

10 mv/s 20m v/s

50 mv/s

100 mv/s

150 mv/s

200 mv/s

250 mv/s

Ag-Sn/Graphite electrode in 1M MeOH+0.5M KOH

10 mV S-1

250 mV S-1

(c)

Fig 4 (a) Cyclic voltammogram of AgeSn/Graphite electrode in different concentration methanol in 0.5M KOH (b) Cyclic voltammogram of Graphite (a), Sn/Graphite (b) and AgeSn/Graphite (c) in 1 M CH3OH containing 0.5 M KOH at the sweep rate of 50 mV/s (c) Cyclic voltammogram of AgeSn/Graphite electrode in a mixture of 1MCH3OHþ0.5M KOH solution at different scan rates (10, 20, 30, 50,100, 150, 200 and 250 mV/s).

Table 1

Electrocatalytic activity of AgeSn/Graphite electrode at different concentrations of methanol in 0.5 M KOH.

Table 2

Comparative electrochemical performance of methanol oxidation on Graphite (a), Sn/Graphite (b) and AgeSn/Graphite (c) electrode measured in a solution of 1M CH3OH in 0.5M KOH at a sweep rate of 50 mV/s.

Electrocatalytic Performance Data

Trang 6

(Epc) values vary; with the AgeSn/Graphite being the most

favor-able catalyst system It displays a higher current density when

compared to the other intermediate states (Sn/Graphite and

Graphite) as shown inFig 4(b)

The silver nanoparticles on graphite are thus capable of

cata-lyzing the oxidation of methanol Theﬁrst step of the oxidation is

the adsorption of methanol on the surface of Ag NPs acting as

catalyst This results in a step by step removal of hydrogen in the

form of hydrogen cations toﬁnally form a silver-carbon residue

The latter reacts with dissociated water toﬁnally release carbon

dioxide In the process, along with the removal of each hydrogen

ion, an electron gets released giving rise to methanol oxidation

current The mechanism can be understood by the following

re-actions[16,29]

CH3OHþ H2/CO2þ 6Hþþ 6e (9)

CH3OHþ Ag/Ag CH2OHþ Hþþ e (10)

Ag CH2OHþ Ag/Ag2 CHOH þ Hþþ e (11)

Ag2 CHOH þ Ag/Ag3 COH þ Hþþ e (12)

Ag3 COH /Ag CO þ 2AgðsÞ þ Hþþ e (13)

Ag CO þ OH/AgðsÞ þ CO2þ Hþþ e (15)

Fig 4(c) represents the cyclic voltammogram, corresponding

to AgeSn/Graphite electrode in 1M CH3OH in 0.5M KOH solution

at various scan rates (v¼ 10e250 mV/s) In the present case, the

-1.0x10-3 -5.0x10-4 0.0

0.0

Potential (V)

10mV/S 20mV/S 30mV/S 40mV/S 50mV/S 60mV/S 70mV/S 80mV/S 90mV/S 100mV/S

10 mV/S

100 mV/S

(a)

Potential (V)

10mV/S 20mV/S 30mV/S 40mV/S 50mV/S 60mV/S 70mV/S 80mV/S 90mV/S 100mV/S

10 mV/S

100 mV/S

Ag-Sn/Graphite electrode in 10 mM of Fe 2+

/Fe 3+

in 0.5 M KCl

(b)

Fig 5 Cyclic voltammogram of (a) Graphite and (b) AgeSn/Graphite electrode in a mixture of 5 mM of Fe 2þ and Fe3þin 0.5M KCl solution at different scan rates (10, 20, 30, 40, 50,

Trang 7

Ipa showed an increase while the cathodic peak current (Ipc)

decreased The peak currents are proportional to the sweep rate,

indicating that the surface reaction of the electrode is conﬁned

Cyclic voltammogram of different sweep rates were performed with Graphite and AgeSn/Graphite carbon paste electrodes in the ferro/ferri system[30] From the cyclic voltammogram of Graphite

-1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 -3.0x10-4

-2.0x10-4 -1.0x10-4 0.0 1.0x10-4 2.0x10-4

Potential (V)

230C

600C Ag-Sn/Graphite Electrode in 1M CH3OH + 0.5 M KOH

Fig 6 Effect of temperature on cyclic voltammogram of methanol oxidation on of AgeSn/Graphite electrode in the temperature range of 25 Ce60 C with a potential sweep rate of

50 mV s1.

Fig 7 Nyquist plots of (a) Graphite (b) Sn/Graphite and (c) AgeSn/Graphite electrode in 5 mM of K3Fe(CN)6

Trang 8

and AgeSn/Graphite carbon paste electrodes (Fig 4(b)), the active

surface area of Graphite and AgeSn/Graphite was estimated using

the RandleseSevecik equation of a reversible process[31]

Ip¼ 2:69 105 n3

A D1

C0 v1

(16)

where Ip is the peak current of active surface area, D is diffusion

coefﬁcient, C0 is concentration of electro active species, A is

active surface area, n is number of electrons involved in the

re-action and nis sweep rate The active surface area of Graphite

and AgeSn/Graphite was calculated to be 6.2479 105cm2and

6.7886 105cm2, respectively On plotting Ipaas a function of

sweep rate, a linear graph was obtained The linearity was more

profound in the scan rate range from 10 to 100 mV/s (Fig 5) The

correlation coefﬁcient (r2) of AgeSn/Graphite was calculated to

be 0.99 The results clearly suggest an adsorption-controlled

process[32]

The temperature dependence on oxidation of 1M methanol in

0.5M KOH, on AgeSn/Graphite electrode was investigated in the

temperature range of 23e60C by cyclic voltammetry (Fig 6) In

this temperature range, the shift in the current and potential of

methanol oxidation is not drastic Nevertheless, it does suggest a

deﬁnite kinetic enhancement with increase in temperature from 23

to 60C[30]

3.6.2 Electrochemical impedance studies

EIS is employed to study the electron transfer between the

electrode surface and electrolyte The impedance spectra for the

AgeSn/Graphite, Sn/Graphite and graphite electrodes system are

represented inFig 7 For the impedance measurement, all

elec-trodes were immersed in 5 mM of [Fe(CN)6]3/4and 0.5 M KCl

solution The analysis was carried out in the frequency range 1 Hz to

1 MHz[33,34] The electroactivity is governed by the following

equation

½FeðCNÞ64/ ½FeðCNÞ6i3þ e (17)

FromFig 7it can be observed that the impedance plot of the

AgeSn/Graphite electrode displays a depressed semicircle for

charge transfer resistance in the high-frequency region, while a

slope related to Warburg impedance in the low-frequency region

The low impedance of AgeSn/Graphite electrode implies a lower

charge transfer resistance, suggesting an easy electrochemical

re-action on this electrode[35e37].Fig 7 also gives the equivalent

circuit of the system in the inset; wherein W is the Warburg

impedance at lower frequency range, which is in series with the

charge transfer resistance (Rct) and parallel to capacitance (C) The

order of charge transfer resistance and corresponding capacitance

for Graphite, Sn/Graphite and AgeSn/Graphite electrodes have

been obtained by ﬁtting experimental data according to the

equivalent circuit[38]and tabulated inTable 3 It can be observed

from the values that a minimum Rctand maximum Cdlis obtained

for AgeSn/Graphite electrode The following result can be

sum-marized from the experiment: Graphite (2.198 108 F) > Sn/

Graphite (1.498 1010F)< AgeSn/Graphite (6.659 107F) This

indicates that AgeSn/Graphite electrode show better electro-catalytic activity when compared to Sn/Graphite electrode

4 Conclusion

In this report, we have successfully prepared an efﬁcient elec-trocatalyst by electroless deposition of silver nanoparticles on activated graphite powder The analytical techniques such as FESEM, PXRD, EDX, and XPES have helped us to substantially infer the supporting data The electrochemical studies of oxidation of methanol in alkaline medium were carried out using CV, while the active surface area of Graphite and AgeSn/Graphite electrodes were calculated using RandleseSevecik equation The capacitance improved and the charge transfer resistance decreased for AgeSn/ Graphite electrode as compared to Sn/Graphite electrode This in-dicates a superior surface catalytic activity of AgeSn/Graphite electrodes The obtained results are encouraging as the prepared graphite supported silver nanoparticles have the potential to deliver as an efﬁcient electrocatalyst for fuel cell applications Acknowledgements

The authors acknowledge the instrumental facilities of PXRD and CV at the Department of Chemistry, Central College, Bangalore University and EIS facility at Rajarajeshwari College of Engineering, Research Centre, Department of Chemistry, Bangalore The authors would also like to extend their acknowledgement to Indian Insti-tute of Science, Bangalore for providing XPES, FESEM and EDX facilities

References

[1] M Montazer, V Allahyarzadeh, Electroless plating of silver nanoparticles/ nanolayer on polyester fabric using AgNO 3 /NaOH and ammonia, Ind Eng Chem Res 52 (2013) 8436e8444

[2] C.J Kirubaharan, D Kalpana, Y.S Lee, A.R Kim, D.J Yoo, K.S Nahm, G.G Kumar, Biomediated silver nanoparticles for the highly selective copper(II) ion sensor applications, Ind Eng Chem Res 51 (2012) 7441e7446

[3] J Chen, W Wang, X Zhang, Y Jin, Microwave-assisted green synthesis of silver nanoparticles by carboxy methyl cellulose sodium and silver nitrate, Mater Chem Phys 108 (2008) 421e424

[4] J Huang, L Lin, Q Li, D Sun, Y Wang, Y Lu, N He, K Yang, X Yang, H Wang,

W Wang, W Lin, Continuous ﬂow biosynthesis of silver nanoparticles by lixivium of sundried Cinnamomum camphora leaf in tubular microreactors, Ind Eng Chem Res 47 (2008) 6081e6090

[5] A Panacek, L Kvitek, R Prucek, M Kolar, R Vecerova, N Pizurova, V.K Sharma, T Nevecna, R Zboril, Silver colloid nanoparticles: synthesis, characterization, and their antibacterial activity, J Phys Chem B 110 (2006) 16248e16253

[6] C.M Ng, P.C Chen, S Manickam, Green high-gravitational synthesis of silver nanoparticles using a rotating packed bed reactor(RPBR), Ind Eng Chem Res.

51 (2012) 5375e5381 [7] E Bulut, M Ozacar, Rapid, facile synthesis of silver nanostructure using hy-drolyzable tannin, Ind Eng Chem Res 48 (2009) 5686e5690

[8] V.K Sharma, R.A Yngard, Y Lin, Silver nanoparticles: green synthesis and their antimicrobial activities, Adv Colloid Interface Sci 145 (2009) 83e96 [9] R.A Khaydarov, Y Estrin, S Evgrafova, T Scheper, C Endres, S.Y Cho, Biogenic Silver nanoparticles: environmental Cacumen platycladi extract: synthesis, formation mechanism, and antibacterial activity, Ind Eng Chem Res 50 (2011) 9095e9106

[10] R Irizarry, L Burwell, M.S Leon-Velazquez, Preparation and formation mechanism of silver particles with spherical open structures, Ind Eng Chem Res 50 (2011) 8023e8033

[11] J Huang, G Zhan, B Zheng, D Sun, F Lu, y Lin, H Chen, Z Zheng, Y Zheng,

Q Li, Biogenic silver nanoparticles Cacumen platycladi extract: synthesis, formation echanism, and antibacterial activity, Ind Eng Chem Res 50 (2011) 9095e9106

[12] S Kheybari, N Samadi, S.V Hosseini, A Fazeli, M.R Fazeli, Synthesis and antimicrobial effects of silver nanoparticles produced by chemical reduction method DARU, J Fac Pharm Tehran Univ Med Sci 18 (2010) 168e172 [13] K.S Chou, Y.C Chang, L.H Chiu, Studies on the continuous precipitation of silver nanoparticles, Ind Eng Chem Res 51 (2012) 4905e4910

[14] J.N Solanki, Z.V.P Murthy, Controlled size silver nanoparticles synthesis with water-in-oil micro emulsion method: a topical review, Ind Eng Chem Res 50 (2011) 12311e12323

Table 3

The electrochemical impedance data of graphite (a), Sn/Graphite (b) and AgeSn/

Graphite (c) electrodes in a 10 mM K3Fe(CN)6 and 0.5 M KCl solution at a sweep

50 mV/s.

Graphite (a) 13.29 1011.19 2.198 10 8 0.1604 10 2

Sn/Graphite (b) 0.001 3523.2 1.498 10 10 0.3918 10 3

AgeSn/Graphite (c) 31.66 64.8 6.659 10 7 0.6467 10 3

Trang 9

[15] M Tsuji, K Matsumoto, P Jiang, R Matsuo, T Xang, K Kamarudin, “Roles of Pt

seeds and chloride anions in the preparationof silver nanorods and nanowires

by microwave-polyol method’, Colloids Surf A316 (2008) 266e277

[16] Q.H Tran, V.Q Nguyen Anh-Tuan Le, Silver nanoparticles: synthesis,

proper-ties, toxicology, applications and perspectives, Adv Nat Sci Nanosci

Nano-technol 4 (2013) 033001e033020

[17] L Tongxiang, G Wenli, Y Yinghui, T Chunhe, Electroless plating silver on

graphite powders the study of its conductive adhesive, Int J Adhesion Adhes.

28 (2007) 55e58

[18] M De, P.S Ghosh, V.M Rotello, Application of nanoparticlesin biology, Adv.

Mater 20 (2008) 4225e4241

[19] A.H Lu, E.L Salabas, F Schuth, Magnetic nanoparticles: a review on

strata-gems of fabrication and its biomedical applications, Angew Chem Int Ed 46

(2007) 1222e1244

[20] R Ghosh, S Chaudhuri, Core/shell nanoparticles classes, properties, synthesis

mechanisms, characterization and applications, Chem Rev 112 (2012)

2373e2433

[21] H Naor, D Avnir, Electroless functionalization of silver ﬁlms by its molecular

doping, ACS Appl Mater Interfaces 7 (2015) 26461e26469

[22] S Weifu, G Chen, L Zheng, Electroless deposition of silver particles on

graphite nanosheets, Scrip Mater 59 (2008) 1031e1034

[23] C Pratapkumar, S.C Prashantha, H Nagabhushana, M.R Anilkumar,

C.R Ravikumar, H.P Nagaswarupa, D.M Jnaneshwara, White light emitting

magnesium aluminate nanophosphor: near ultra violet excited

photo-luminescence, photometric characteristics and its UV photocatalytic activity,

J Alloy Comp 728 (2017) 1124e1138

[24] V Allahyarzadeh, M Montazer, N Hemmati Nejad, N Samadi, In situ

syn-thesis of nano silver on polyester using NaOH/Nano TiO 2 , J Appl Polym Sci.

129 (2013) 892e900

[25] Mashentsev Borgekova, S.K Kozlovskiya, Russako va, M Zdorovetsa,

Tem-perature dependent catalytic activityof Ag/PET ion-track membranes

com-posites, Acta Phys Pol 8 (2015) 871e874

[26] M.S Risbud, S Baxter, M.S Kazacos, Preparation of nickel modiﬁed carbon

ﬁbre electrodes and their application for methanol oxidation, Open Fuel

En-ergy Sci J 5 (2012) 9e20

[27] L Yuan, L Jiang, J Liu, Z Xia, S Wang, S Gongquan, Facile synthesis of silver

nanoparticles supported on three dimensional grapheme oxide/carbon block

composite and its application for oxygen reduction reaction, Electrochemical

Acta 135 (2014) 168e174

[28] G Orozco, M.C Perez, A Rincon, C Gutierrez, Electrooxidation of methanol on

silver in alkaline medium, J Electroanal Chem 495 (2000) 71e78

[29] D.J Guo, H.L Li, Highly Dispersed Ag Nanoparticles on Functional MWNT Surfaces for Methanol Oxidation in Alkaline Solution Carbon, vol 43, 2005,

pp 1259e1264 [30] G Krishnamurthy, M.S Shivakumar, Electroless deposition of Nano sized Nickel over Graphite substrate with better coating coverage and catalytic activity for Fuel Cell application, J Appl Electrochem 47 (2017) 519e529 [31] C Sarika, M.S Shivakumar, C Shivakumara, G Krishnamurthy, B Narasimha Murthy, I.C Lekshmi, A novel amperometric catechol biosensor based ona

-Fe 2 O 3 nanocrystals-modiﬁed carbon paste electrode, Artif Cell Nanomed Biotech 45 (2016) 625e634

[32] M.S Shivakumar, G Krishnamurthy, Decoration of copper nanoparticles on multiwalled carbon nanotubes and the study of electrocatalytic activity for methanol oxidation, Mater Today Proc 4 (2017) 12012e12020

[33] H.R Raveesha, S Nayana, D.R Vasudha, J.P Shabaaz Begum, S Pratibha, C.R Ravikumara, N Dhananjaya, The electrochemical behavior, antifungal and cytotoxic activities of phytofabricated MgO nanoparticles using Withania somnifera leaf extract, J Sci Adv Mat Dev 4 (2019) 57e65

[34] C.R Ravikumar, M.R AnilKumar, H.P Nagaswarupa, S.C Prashantha, Aarti

S Bhatt, M.S Santosh, D Kuznetsov, CuO embedded b-Ni(OH) 2 nano-composite as advanced electrode materials for supercapacitors, J Alloy Comp.

736 (2018) 332e339 [35] C.R Ravikumar, P Kotteeswaran, V Bheema Raju, A Muruganb, M.S Santosh, H.P Nagaswarupa, S.C Prashanthaa, M.R Anil Kumar, M.S Shivakumar, In-ﬂuence of zinc additive and pH on the electrochemical activities ofb-nickel hydroxide materials and its applications in secondary batteries, J Energy Stor.

9 (2017) 12e24 [36] C.R Ravikumar, P Kotteeswaran, A Murugan, V Bheema Raju, M.S Santosh, H.P Nagaswarupa, H Nagabhushana, S.C Prashantha, M.R Anil Kumar,

K Gurushantha, Electrochemical studies of nano metal oxide reinforced nickel hydroxide materials for energy storage applications, J Mater Today Proc 4 (2017) 12205e12214 (ISSN: 2214-7853)

[37] K.M Girish, S.C Prashantha, H Nagabhushana, C.R Ravikumar, H.P Nagaswarupa, Ramachandra Naik, H.B Premakumar, B Umesh, Multi-functional Zn 2 TiO 4 :Sm3þnanopowders: excellent performance as electro-chemical sensor and UV photocatalyst, J Sci Adv Mater Dev 3 (2018) 151e160

[38] M.R Anil Kumar, H.P Nagaswarupa, C.R Ravikumar, S.C Prashantha,

H Nagabhushana, Aarti S Bhatt, Green engineered nano MgO and ZnO doped with Sm3þ: synthesis and a comparison study on their characterization, PC activity and electrochemical properties, J Phys Chem Solids 127 (2019) 127e139

Định dạng
Số trang	9
Dung lượng	1,34 MB