Research Article Synthesis and Characterization of Cobalt ...Research Article Synthesis and...

Research ArticleSynthesis and Characterization of Cobalt NanoparticlesUsing Hydrazine and Citric Acid

S A Salman12 T Usami3 K Kuroda1 and M Okido1

1 EcoTopia Science Institute Nagoya University Furo-cho Chikusa Nagoya 464-8603 Japan2Graduate School of Engineering Al-Azhar University Nasr City Cairo 11371 Egypt3 Graduate School of Engineering Nagoya University Furo-cho Chikusa-ku Nagoya 464-8603 Japan

Correspondence should be addressed to S A Salman sasalmanyahoocom

Received 20 September 2013 Revised 24 January 2014 Accepted 9 February 2014 Published 13 March 2014

Academic Editor Sakhrat Khizroev

Copyright copy 2014 S A Salman et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Cobalt nanoparticles were produced by employing the liquid-phase reduction method and hydrazine The effect of citric acidadditives on the formation and growth mechanism of cobalt nanoparticles was investigated using polarization methodsThe cobaltnanoparticles produced in 02M cobalt sulfate and 5M hydrazine at 298K had a spherical shape with a diameter of 400 nm Thedendritic nanoparticles formedwith the decreasing of hydrazine concentration at 298 KOn the other hand dendritic large particlesare confirmed at 353K It was confirmed that the reduction reaction progressed with the addition of citric acid and a hexagonalclose-packed (120576Co) phase was formed

1 Introduction

Much work is presently being done around the world todevelop hydrogen and fuel-cell technologies so that they willbe cost-competitive in diverse applications Platinum workswell as a catalyst in hydrogen fuel cells however it has at leasttwo drawbacks in that it is expensive and degrades over timeEliminating the precious metal platinum would solve a sig-nificant economic challenge that has thwarted thewidespreaduse of large-scale hydrogen fuel-cell systems A new catalyticmaterial based on the element cobalt has been proposed asan alternative to platinum in recent years and might allowthe manufacturing of cheaper and more durable hydrogenfuel cells Cobalt is considered to be the first catalyst madefrom nonprecious metal with properties closely matchingwith those of platinum [1] Cobalt serves also as a modelsystem for the macroscopic magnetic response because thelow to moderate crystal anisotropy allows the effects ofsize shape internal crystal structure and surface anisotropyto be observed in a single system [2 3] The low crystalanisotropy of cobalt also promotes their study as a modelsystem for the effects of size shape crystal structure andsurface anisotropy on their macroscopic magnetic response

A variety of methods for the preparation of magnetic colloiddispersions have been reported Cobalt is one of the mostimportant ferromagnetic metals due to its three metastablephases with different crystallographic structures namely thehexagonal closed packed (hcp) phase the face-centered cubic(fcc) phase and the epsilon phase [4 5]

Synthesizing metallic nanoparticles following wet-chem-istry routes is a powerful way of obtaining a reproduciblemacroscopic amount of homogeneous sample [6] Severalwet-chemical methods have been developed to synthe-size cobalt crystals with different morphologies for exam-ple pyrolysis solvothermal and hydrothermal decomposi-tion microfluidic synthesis modified polyol processes andtemplate-based methods [7ndash14] It has been reported thatliquid-phase reduction methods are relatively simple and donot require special equipmentMoreover they are consideredto be less expensive and quicker to implement which aredesirable qualities for future attempts of large-scale produc-tion [15]

Much attention has been paid to the characteristics ofcobalt nanoparticles however there has been little researchon the growth mechanism of cobalt nanoparticles

Hindawi Publishing CorporationJournal of NanotechnologyVolume 2014 Article ID 525193 6 pageshttpdxdoiorg1011552014525193

2 Journal of Nanotechnology

The shape and size of the nanoparticles influence thephysical characterization of these novel materials

Therefore the control of shape and size will increase thepossibility of commercial widespread of these materials Soit is very important to study the effect of kinetic parametersfor example temperature and time to explain the mechanismof the morphology of the particles from the fundamentalviewpoint

In this study we attempted to synthesize cobalt nanopar-ticles at room temperature by employing the liquid-phasereduction method and revealing the formation mechanismof particulates and the reaction mechanism of the reducingagent Hydrazine (N

2H4) was used as a reducing agent in a

solution containing a cobalt compound and Co2+ to precipi-tate the cobalt Citric acid is a unique capping agent to protectand stabilize metal nanoparticles [16 17] therefore the effectof citric acid additives on the shape and size of producednanoparticles was investigated

2 Experimental

21 Anodic Polarization A 1moldm3 solution of hydrazinemonohydrate (N

2H4sdotH2O 5006 MW) was dissolved in

200 dm3 distilled water and 02M sodium citrate dihydrate(Na3C6H5O7sdot2H2O) was added to the solution Solutions

of NaOH and H2SO4were used to adjust the pH After

adjusting the pH dissolved oxygen was removed by bubblingargon through the solution for 30min Polarization mea-surements were made using a three-electrode potentiostat ACo plate with surface area of 1 cm2 platinum coil (gt1 cm2)and AgAgCl sat KCl were used as working counter andreference electrodes respectively A saturated KCl agar saltbridge was used as the liquid junction between the referenceelectrode and electrolyte The mixture was stirred at a con-stant speed by a magnetic stirrer during the experiment Thecobalt used had a purity of 999 The anodic polarizationmeasurement was made at a potential sweep rate of 1mVsminus1

22 Synthesis of Cobalt Nanoparticles Hydrazine monohy-drate and cobalt sulfate heptahydrate (CoSO

4sdot7H2O) were

used as raw materials A 04M solution of sodium citratedihydrate was added to 20mL of 02M aqueous cobalt sulfatesolution The pH of the solution was adjusted using NaOHand M H

2SO4 and the solution was deaerated by bubbling

argon through the solution for 30min The solution wasmaintained at a predetermined temperature and allowed toreact for 60 to 120min After the solution was centrifugedsuspensions were removed and washed several times withdistilled water and dried using a vacuum dryerThe shapes ofnanoparticles were observed with a scanning electronmicro-scope (SEM)The phase structures were identified employingX-ray diffraction (XRD) The redox potential (mixed poten-tial) at the working electrode was measured throughout thereduction reaction using a potentiostat A cobalt plate withsurface area of 1 cm2 and AgAgCl sat KCl was used as theworking and reference electrodes respectively

3 Results and Discussion

31 Reducing Power of Hydrazine It is more important tomeasure the oxidation potential of the reducing agent used inthe liquid-phase reductionmethod than the reduction poten-tial of themetal Tomeasure the reducing power of hydrazinealone the anodic polarization was carried out at 353 and298K at various solution pH values as shown in Figures 1(a)and 1(b) The oxidation potential decreased and became lessnoble with an increase in pH The oxidation of hydrazinedepends on pH because the reaction consumes OHminus asshown in oxidation reaction equation

N2H4+ 4OHminus 997888rarr N

2+ 4H2O + 4119890minus (1)

At a high concentration of OHminus the oxidation reaction islikely to occur and the potential decreases

In addition the current density sharply increased at pHge13 at 298K and pH ge12 at 353K It is known that hydrazineis a highly reactive base and reducing agent it acts morestrongly as a reducing agent at high pH values

The polarization curves of a mixed bath of citric acid andhydrazine at 353 and 298K are shown in Figures 1(c) and 1(d)The oxidation potential decreased and became less noble withthe addition of citric acid which indicates that the citric acidimproved the reducing power of hydrazine

Figure 2 shows the potential-pH diagram is drawn usingthe Nernst equation The figure shows that it is possible tosynthesize cobalt particles using hydrazine because the oxi-dation potential of hydrazine is less noble than the reductionpotential of cobalt Furthermore the measured oxidationpotential of hydrazine is similar to the theoretical valuescalculated using the Nernst equation

Mixed potential with Co and Hydrazine is the poten-tial region between Co reduction (theoretical value) andhydrazine oxidation (experimental value) The oxidationpotential does not change with addition of citric acid whichindicates that no complex ion was formed as shown inFigure 2

Consider the following

119877119879

119911119865

ln119886ox119886red=

8314 times 119879

4 times 96485

times 2303 log [H+]4

= minus

8314 times 2303 times 119879

96485

(V) pH

= minus (00591V) pH (298K)

= minus (00700V) pH (353K)

(2)

In the equations 119877 is the gas constant 119879 the absolutetemperature 119911 the valence of the ion solution 119886 the activityand 119865 Faradayrsquos constant

Thepotential-pHdiagram shows a notable decrease in thepotential at both applied temperatures with the addition ofcitric acid Therefore the addition of citric acid in the liquid-phase reduction method can improve the reducing power ofhydrazine at low and high pH values

Journal of Nanotechnology 3

Curr

ent d

ensit

yi

(mA

middotcmminus

2)

minus11 minus1 minus09 minus07 minus06 minus05minus080

1

2

3

4

5 298 K

pH 14

pH 13

pH 12

pH 11

pH 10

Potential E (V versus SHE)

(a)Cu

rren

t den

sity

i(m

Amiddotcm

minus2)

minus11 minus1 minus09 minus07 minus06minus080

1

2

3

4

5 298 K

pH 14

pH 13

pH 12

pH 11

pH 10


(b)

pH 14

pH 13

pH 12

pH 11

pH 10

Curr

ent d

ensit

yi

(mA

middotcmminus

2)


1

2

3

4

5 353 K


(c)

Curr

ent d

ensit

yi

(mA

middotcmminus

2)


1

2

3

4

5 353 K

pH 14

pH 13

pH 12

pH 11

pH 10


(d)

Figure 1 Anodic polarization measurements of hydrazine (a b) and hydrazine + citric acid (c d)

pH1 3 5 7 9 11 13 15

298 K0

minus02

minus04

minus06

minus08

minus1

minus12

Co2+

Co

Co(OH)2

[Co2+] = 01 MPote

ntia

lE

(V v

ersu

s SH

E)

(a)

pH1 3 5 7 9 11 13 15

353 K0

minus02

minus04

minus06

minus08

minus1

minus12

Co2+

Co

Co(OH)2

[Co2+] = 01 MPote

ntia

lE

(V v

ersu

s SH

E)

(b)

Figure 2 Oxidation potential of hydrazine in a potential-pH diagram of the Co-H2O system


20

(a)

(b)

40 60 80

2120579 (deg CuKa)

Co(OH)2

120576Co (hcp)

Inte

nsity

(au

)

Figure 3 XRD patterns of cobalt nanoparticles after 60min reac-tion in a solution containing 5M hydrazine without citric acid (a)and with citric acid (b)

Higher reducing power was observed at a high pH valueof 14 therefore the pH of the solution used in the followingnanoparticle synthesis experiments was set to 14

32 Effect of Citric Acid Additives The effect of adding citricacid on the phase structure is shown in Figure 3 The XRDresults show the phase structure of the produced cobaltnanoparticles after 60min reaction in a solution containing5M hydrazine at a temperature of 298K When hydrazinealone was used several peaks of Co (OH)

2were detected

as shown in Figure 3(a) The reduction reaction progressedby adding the citric acid and a hexagonal close-packed (120576Co)phase was formed as shown in Figure 3(b)

33 Cathode PolarizationMeasurement A cathodic polariza-tionmeasurementwas carried out to evaluate the role of citricacid

Figure 4 shows that the cathode current density increasedwith the addition of citric acid indicating a high reductionreaction rate Therefore the addition of citric acid caneffectively improve the reducing power and reaction speed

0

minus05

minus1minus12 minus1 minus08 minus06

Without citric acidWith citric acid

Curr

ent d

ensit

yi

(mA

middotcmminus

2)


Figure 4 Cathodic polarization measurements of hydrazine withand without citric acid at 298K

The reduction of cobalt in the liquid-phase reductionmethod is thought to proceed according to

Co(OH)2997888rarr Co2+ + 2OHminus (3)

Co2+ + C6H5O7

3minus997888rarr Co(C

6H5O7)minus (4)

2Co(OH)2+ N2H4997888rarr 2Co + N

2+ 4H2O (5)

Thedissociation ofCo(OH)2toCo2+ which is considered

the starting point of the reduction reaction is affected by thespeed of the reduction reaction

SEM images of the nanoparticles produced at 298 and353K for various hydrazine concentrations are shown inFigure 5 The reaction time was set to 120min for 2Mhydrazine 90min for 3M hydrazine and 60min for 5Mhydrazine Figure 5(a) shows that the cobalt nanoparticlesproduced in 5M hydrazine at 298K have a spherical shapewith a diameter of 400 nm As the concentration of hydrazinedecreases it is confirmed that dendritic nanoparticles formand the crystal grows in one direction This hydrazinediffusion is low at low temperature and the nucleation thattakes fast and small particles was formed At 353K dendriticlarge particles are confirmed as shown in Figures 5(d) 5(e)and 5(f) the diffusion is of relatively high rate So the crystalsgrew in two directions at high rate even when the hydrazineconcentration was 5M

4 Conclusions

We investigated the Synthesis and formation mechanismof cobalt particles in the liquid-phase reduction methodHydrazine was found to have the reducing power requiredfor the reduction of cobalt Furthermore the addition of citricacid improved the reducing power of hydrazineThe addition


500 nm

298 K 353 K

298 K 353 K

298 K 353 K

5 120583m

1 120583m 10 120583m

2 120583m10 120583m

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

(a)

(b)

(c)

(d)

(e)

(f)

Figure 5 SEM images of cobalt nanoparticles produced at 298 and 353K at various hydrazine concentrations

of citric acid improved the rate of the reduction reactionand the cobalt nanoparticles produced in 5M hydrazine hada spherical shape with a diameter of 400 nm As the con-centration of hydrazine decreased dendritic nanoparticlesformed at 298K On the other hand dendritic large particlesare confirmed at 353K It was confirmed that the reductionreaction progressed by adding citric acid and a hexagonalclose-packed (120576Co) phase was formed

Conflict of Interests

The authors declare that there is no conflict of interests

Acknowledgments

The authors gratefully acknowledge the Aichi Center forIndustry and Science Technology the Ministry of Education


Culture Sports Science and Technology Japan and theMinistry of Higher Education Egypt

References

[1] Y Yu A Mendoza-Garcia B Ning and S Sun ldquoCobalt-substituted magnetite nanoparticles and their assembly intoferrimagnetic nanoparticle arraysrdquo Advanced Materials vol 25no 22 pp 3090ndash3094 2013

[2] V F Puntes K M Krishnan and A P Alivisatos ldquoColloidalnanocrystal shape and size control the case of cobaltrdquo Sciencevol 291 no 5511 pp 2115ndash2117 2001

[3] V Skumryev S Stoyanov Y Zhang G Hadjipanayis D Givordand J Nogues ldquoBeating the superparamagnetic limit withexchange biasrdquo Nature vol 423 no 6942 pp 850ndash853 2003

[4] B K Pandey A K Shahi R K Swarnkar and R Gopal ldquoMag-netic property of novel cobalt sulfate nanoparticles synthesizedby pulsed laser ablationrdquo Science of Advanced Materials vol 4no 3-4 pp 537ndash543 2012

[5] A-H Lu E L Salabas and F Schuth ldquoMagnetic nanoparticlessynthesis protection functionalization and applicationrdquoAnge-wandte Chemie International Edition vol 46 no 8 pp 1222ndash1244 2007

[6] V F Puntes K Krishnan and A P Alivisatosa ldquoSynthesis ofcolloidal cobalt nanoparticles with controlled size and shapesrdquoTopics in Catalysis vol 19 no 2 pp 145ndash148 2002

[7] L Guo F Liang X G Wen et al ldquoUniform magnetic chainsof hollow cobalt mesospheres from one-pot synthesis and theirassembly in solutionrdquoAdvanced FunctionalMaterials vol 17 no3 pp 425ndash430 2007

[8] S-H Liu H Gao E Ye et al ldquoGraphitically encapsulated cobaltnanocrystal assembliesrdquoChemical Communications vol 46 no26 pp 4749ndash4751 2010

[9] X Wang F Yuan P Hu L Yu and L Bai ldquoSelf-assembledgrowth of hollow spheres with octahedron-like Co nanocrystalsvia one-pot solution fabricationrdquoThe Journal of Physical Chem-istry C vol 112 no 24 pp 8773ndash8778 2008

[10] F Cao R Deng J Tang S Song Y Lei and H Zhang ldquoCobaltand nickel with various morphologies mineralizer-assistedsynthesis formation mechanism and magnetic propertiesrdquoCrystEngComm vol 13 no 1 pp 223ndash229 2011

[11] Y Song H Modrow L L Henry et al ldquoMicrofluidic synthesisof cobalt nanoparticlesrdquo Chemistry of Materials vol 18 no 12pp 2817ndash2827 2006

[12] A Dakhlaoui L S Smiri G Babadjian F Schoenstein PMolinie and N Jouini ldquoControlled elaboration and magneticproperties of submicrometric cobalt fibersrdquo Journal of PhysicalChemistry C vol 112 no 37 pp 14348ndash14354 2008

[13] DD Li R SThompson G Bergmann and J G Lu ldquoTemplate-based synthesis and magnetic properties of cobalt nanotubearraysrdquo Advanced Materials vol 20 no 23 pp 4575ndash45782008


[15] Z G Wu M Munoz and O Montero ldquoThe synthesis of nickelnanoparticles by hydrazine reductionrdquo Advanced Powder Tech-nology no 212 pp 165ndash168 2010

[16] K A Barnes A Karim J F Douglas A I Nakatani H Gruelland E J Amis ldquoSuppression of dewetting in nanoparticle-filled

polymer filmsrdquo Macromolecules vol 33 no 11 pp 4177ndash41852000

[17] B J Kim J Bang C J Hawker and E J Kramer ldquoEffect ofareal chain density on the location of polymer-modified goldnanoparticles in a block copolymer templaterdquoMacromoleculesvol 39 no 12 pp 4108ndash4114 2006

Submit your manuscripts athttpwwwhindawicom

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CompositesJournal of

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Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


The shape and size of the nanoparticles influence thephysical characterization of these novel materials

Therefore the control of shape and size will increase thepossibility of commercial widespread of these materials Soit is very important to study the effect of kinetic parametersfor example temperature and time to explain the mechanismof the morphology of the particles from the fundamentalviewpoint

In this study we attempted to synthesize cobalt nanopar-ticles at room temperature by employing the liquid-phasereduction method and revealing the formation mechanismof particulates and the reaction mechanism of the reducingagent Hydrazine (N

2H4) was used as a reducing agent in a

solution containing a cobalt compound and Co2+ to precipi-tate the cobalt Citric acid is a unique capping agent to protectand stabilize metal nanoparticles [16 17] therefore the effectof citric acid additives on the shape and size of producednanoparticles was investigated

2 Experimental

21 Anodic Polarization A 1moldm3 solution of hydrazinemonohydrate (N

2H4sdotH2O 5006 MW) was dissolved in

200 dm3 distilled water and 02M sodium citrate dihydrate(Na3C6H5O7sdot2H2O) was added to the solution Solutions

of NaOH and H2SO4were used to adjust the pH After

adjusting the pH dissolved oxygen was removed by bubblingargon through the solution for 30min Polarization mea-surements were made using a three-electrode potentiostat ACo plate with surface area of 1 cm2 platinum coil (gt1 cm2)and AgAgCl sat KCl were used as working counter andreference electrodes respectively A saturated KCl agar saltbridge was used as the liquid junction between the referenceelectrode and electrolyte The mixture was stirred at a con-stant speed by a magnetic stirrer during the experiment Thecobalt used had a purity of 999 The anodic polarizationmeasurement was made at a potential sweep rate of 1mVsminus1

22 Synthesis of Cobalt Nanoparticles Hydrazine monohy-drate and cobalt sulfate heptahydrate (CoSO

4sdot7H2O) were

used as raw materials A 04M solution of sodium citratedihydrate was added to 20mL of 02M aqueous cobalt sulfatesolution The pH of the solution was adjusted using NaOHand M H

2SO4 and the solution was deaerated by bubbling

argon through the solution for 30min The solution wasmaintained at a predetermined temperature and allowed toreact for 60 to 120min After the solution was centrifugedsuspensions were removed and washed several times withdistilled water and dried using a vacuum dryerThe shapes ofnanoparticles were observed with a scanning electronmicro-scope (SEM)The phase structures were identified employingX-ray diffraction (XRD) The redox potential (mixed poten-tial) at the working electrode was measured throughout thereduction reaction using a potentiostat A cobalt plate withsurface area of 1 cm2 and AgAgCl sat KCl was used as theworking and reference electrodes respectively

3 Results and Discussion

31 Reducing Power of Hydrazine It is more important tomeasure the oxidation potential of the reducing agent used inthe liquid-phase reductionmethod than the reduction poten-tial of themetal Tomeasure the reducing power of hydrazinealone the anodic polarization was carried out at 353 and298K at various solution pH values as shown in Figures 1(a)and 1(b) The oxidation potential decreased and became lessnoble with an increase in pH The oxidation of hydrazinedepends on pH because the reaction consumes OHminus asshown in oxidation reaction equation

N2H4+ 4OHminus 997888rarr N

2+ 4H2O + 4119890minus (1)

At a high concentration of OHminus the oxidation reaction islikely to occur and the potential decreases

In addition the current density sharply increased at pHge13 at 298K and pH ge12 at 353K It is known that hydrazineis a highly reactive base and reducing agent it acts morestrongly as a reducing agent at high pH values

The polarization curves of a mixed bath of citric acid andhydrazine at 353 and 298K are shown in Figures 1(c) and 1(d)The oxidation potential decreased and became less noble withthe addition of citric acid which indicates that the citric acidimproved the reducing power of hydrazine

Figure 2 shows the potential-pH diagram is drawn usingthe Nernst equation The figure shows that it is possible tosynthesize cobalt particles using hydrazine because the oxi-dation potential of hydrazine is less noble than the reductionpotential of cobalt Furthermore the measured oxidationpotential of hydrazine is similar to the theoretical valuescalculated using the Nernst equation

Mixed potential with Co and Hydrazine is the poten-tial region between Co reduction (theoretical value) andhydrazine oxidation (experimental value) The oxidationpotential does not change with addition of citric acid whichindicates that no complex ion was formed as shown inFigure 2

Consider the following

119877119879

119911119865

ln119886ox119886red=

8314 times 119879

4 times 96485

times 2303 log [H+]4

= minus

8314 times 2303 times 119879

96485

(V) pH

= minus (00591V) pH (298K)

= minus (00700V) pH (353K)

(2)

In the equations 119877 is the gas constant 119879 the absolutetemperature 119911 the valence of the ion solution 119886 the activityand 119865 Faradayrsquos constant

Thepotential-pHdiagram shows a notable decrease in thepotential at both applied temperatures with the addition ofcitric acid Therefore the addition of citric acid in the liquid-phase reduction method can improve the reducing power ofhydrazine at low and high pH values


Curr

ent d

ensit

yi

(mA

middotcmminus

2)


1

2

3

4

5 298 K

pH 14

pH 13

pH 12

pH 11

pH 10


(a)Cu

rren

t den

sity

i(m

Amiddotcm

minus2)


1

2

3

4

5 298 K

pH 14

pH 13

pH 12

pH 11

pH 10


(b)

pH 14

pH 13

pH 12

pH 11

pH 10

Curr

ent d

ensit

yi

(mA

middotcmminus

2)


1

2

3

4

5 353 K


(c)

Curr

ent d

ensit

yi

(mA

middotcmminus

2)


1

2

3

4

5 353 K

pH 14

pH 13

pH 12

pH 11

pH 10


(d)


pH1 3 5 7 9 11 13 15

298 K0

minus02

minus04

minus06

minus08

minus1

minus12

Co2+

Co

Co(OH)2

[Co2+] = 01 MPote

ntia

lE

(V v

ersu

s SH

E)

(a)

pH1 3 5 7 9 11 13 15

353 K0

minus02

minus04

minus06

minus08

minus1

minus12

Co2+

Co

Co(OH)2

[Co2+] = 01 MPote

ntia

lE

(V v

ersu

s SH

E)

(b)



20

(a)

(b)

40 60 80

2120579 (deg CuKa)

Co(OH)2

120576Co (hcp)

Inte

nsity

(au

)




2were detected




0

minus05



Curr

ent d

ensit

yi

(mA

middotcmminus

2)





Co2+ + C6H5O7


6H5O7)minus (4)


2+ 4H2O (5)




4 Conclusions



500 nm

298 K 353 K

298 K 353 K

298 K 353 K

5 120583m

1 120583m 10 120583m

2 120583m10 120583m

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

(a)

(b)

(c)

(d)

(e)

(f)





Acknowledgments




References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Curr

ent d

ensit

yi

(mA

middotcmminus

2)


1

2

3

4

5 298 K

pH 14

pH 13

pH 12

pH 11

pH 10


(a)Cu

rren

t den

sity

i(m

Amiddotcm

minus2)


1

2

3

4

5 298 K

pH 14

pH 13

pH 12

pH 11

pH 10


(b)

pH 14

pH 13

pH 12

pH 11

pH 10

Curr

ent d

ensit

yi

(mA

middotcmminus

2)


1

2

3

4

5 353 K


(c)

Curr

ent d

ensit

yi

(mA

middotcmminus

2)


1

2

3

4

5 353 K

pH 14

pH 13

pH 12

pH 11

pH 10


(d)


pH1 3 5 7 9 11 13 15

298 K0

minus02

minus04

minus06

minus08

minus1

minus12

Co2+

Co

Co(OH)2

[Co2+] = 01 MPote

ntia

lE

(V v

ersu

s SH

E)

(a)

pH1 3 5 7 9 11 13 15

353 K0

minus02

minus04

minus06

minus08

minus1

minus12

Co2+

Co

Co(OH)2

[Co2+] = 01 MPote

ntia

lE

(V v

ersu

s SH

E)

(b)



20

(a)

(b)

40 60 80

2120579 (deg CuKa)

Co(OH)2

120576Co (hcp)

Inte

nsity

(au

)




2were detected




0

minus05



Curr

ent d

ensit

yi

(mA

middotcmminus

2)





Co2+ + C6H5O7


6H5O7)minus (4)


2+ 4H2O (5)




4 Conclusions



500 nm

298 K 353 K

298 K 353 K

298 K 353 K

5 120583m

1 120583m 10 120583m

2 120583m10 120583m

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

(a)

(b)

(c)

(d)

(e)

(f)





Acknowledgments




References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




20

(a)

(b)

40 60 80

2120579 (deg CuKa)

Co(OH)2

120576Co (hcp)

Inte

nsity

(au

)




2were detected




0

minus05



Curr

ent d

ensit

yi

(mA

middotcmminus

2)





Co2+ + C6H5O7


6H5O7)minus (4)


2+ 4H2O (5)




4 Conclusions



500 nm

298 K 353 K

298 K 353 K

298 K 353 K

5 120583m

1 120583m 10 120583m

2 120583m10 120583m

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

(a)

(b)

(c)

(d)

(e)

(f)





Acknowledgments




References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




500 nm

298 K 353 K

298 K 353 K

298 K 353 K

5 120583m

1 120583m 10 120583m

2 120583m10 120583m

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

5M

hyd

razi

ne3

M h

ydra

zine

2M

hyd

razi

ne

(a)

(b)

(c)

(d)

(e)

(f)





Acknowledgments




References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Synthesis and Characterization of Cobalt ...Research Article Synthesis and...

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