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Pourbaix

Pourbaix Diagrams for Systems Involving Metal Complexes and Intermetallic

Compounds: Their Construction and Application

Kuniaki Murase

Received February 21, 2014

Fundamental aspects of potential-pH diagrams for systems containing ligand and/or additional

metal components to form stable complexes and/or intermetallic compounds are described by sev-

eral practical examples. The diagrams provide deeper thermodynamic insights into a variety of

aqueous electrochemical processes, such as electrodeposition and electrometallurgy.

18 A. Volta

pH hydrogen

ion exponent

H2O

pH

Zn2+

Zn(OH)2

ZnO22–

606-8501

Corresponding author : Department of Mate-

rials Science and Engineering, Kyoto Uni-

versity, Yoshida-hommachi, Sakyo-ku, Kyoto

606-8501, Japan.

E-mail: [email protected].

35

Review of Polarography, Vol.60, No.1, (2014)

NH3 NH4+

–

NH4+ = NH3 + H

+ (1)

pKa

pH = 9.3

NH4+

NH3

Zn2+

Zn2+

+ 2e = Zn (2)

H+

ZnO22–

ZnO22–

+ 4H+ + 2e = Zn + 2H2O (3)

H+

Nernst

(2) pH

(3)

pH

Zn(NH3)42+

pH (1) pKa

pH > 10.3

Zn(NH3)42+

+ 2e = Zn + 4NH3 (4)

H+

pH pKa pH < 8.3

Zn(NH3)42+

+ 4H+ + 2e

= Zn + 4NH4+ (5)

NH4+

H+

(4) pH

(5)

pH

E

pH

–

pH

Potential-pH diagram

pH University of Brus-

sels Marcel Pourbaix Pourbaix

Pourbaix diagram

Pourbaix pH

Charlot1)

pH

Pourbaix Atlas of Electro-

chemical Equilibria in Aqueous Solutions 2)

pH

pH Zn-H2O

Cu-H2O

pH

FactSage

www.factsage.com HSC Chemistry

www.hsc-chemistry.net

pH

pH

36


pH3,4)

4) J-Stage

pH

Pourbaix Zn-H2O

Cu-H2O pH

pH

pH

5)

Zn-H2O pH 25 °C

Zn-H2O pH 25 °C

(2)

pH

pH

(3)

pH

Zn2+

ZnO22–

Zn(OH)2

Zn2+

+ 2H2O = Zn(OH)2 + 2H+ (6)

Zn(OH)2 = ZnO22–

+ 2H+ (7)

–

1 10–2

10–4

10–6

Zn2+

ZnO22–

1 mol dm–3

Zn2+

1

0.01 mol dm–3

Zn2+

10–2

10–6

Zn(OH)2 + 2H+ + 2e = Zn + 2H2O (8)

pH

2H+ + 2e = H2

2H2O + 2e = H2 + 2OH–

(9)

O2 + 4H+ + 4e = 2H2O

O2 + 2H2O + 4e = 4OH–

(10)

37


pH2 = pO2 = 1 atm

H2O H2 O2 H2O

Zn

Zn Zn2+

Cu2+

Cu

Zn2+

+ 2e = Zn

E° = –0.763 V vs. SHE (2)

Cu2+

+ 2e = Cu

E° = +0.337 V vs. SHE (11)

Zn + Cu2+

Zn2+

+ Cu (12)

(12)

ΔG

Zn-H2O aZn2+ = 10–6

Cu-H2O

aCu2+ = 1 pH

Zn Cu2+

Fe-H2O

pH

Fe2+

Fe2O3

FeOOH

Fe2O3 + 6H+ + 2e = 2Fe

2+ + 3H2O (13)

O2 + 4H+ + 4e = 2H2O (10)

4Fe2+

+ O2 + 4H2O

2Fe2O3 + 8H+ (14)

pH

Zn-H2O Cu-H2O

pH 25 °C

aZn2+ = 10–6

aCu2+ = 1

Fe-H2O pH 25 °C

38


pH

Cl–

NH3 CN–

pH

Au+ Au

3+

Au(CN)2–

Au+ Au

3+

pH

pH

Cu-

-H2O pH

Cu2O6)

Cu(II)

Cu- -H2O pH

25 °C aCu(II) = 1 3 mol dm–3

aCl– = 5

7) Cu-Cl-H2O

CuCl43–

pH pCl

aCl–

–log aCl– pCl

pH = 0

pCl

39


pCl = –0.2 0.4

CuCl

Cu-Cl-H2O (a) pH

25 °C aCu(II) = 10–6

aCl– = 5 (b)

pCl pH = 0

pH

Cd-H2O

Cd-H2O

pH

Cd2+

Cd Cd(OH)2

Cd-NH3-H2O

pH

Cd(NH3)42+

[NH3]total

[NH3] +

[NH4+]

Cd(NH3)42+

(a) Cd-H2O (b-d)

Cd-NH3-H2O pH 25 °C

aCd(II) = 10–2

[NH3]total =

[NH3] + [NH4+] (b) 5.0 mol dm

–3(c) 1.0

mol dm–3

(d) 0.5 mol dm–3

40


Cd(NH3)x2+

x = 1 6

Cd-NH3-H2O

pH

NH3

NH3

aNH3pNH3 = –log aNH3

pNH3 pH8)

pH

pH pNH3

NH3

NH4+

Cd-NH3-H2O pNH3 pH

25 °C aCd(II) = 10–2

ABCD [NH3]total =

[NH3] + [NH4+] = 5.0 mol dm

–3

–

NH4+ = NH3 + H

+ (1)

NH4+

aNH4+ (1)

Ka = aH+ aNH3aNH4

+

pH pNH3

pH + pNH3 = pKa – log aNH4+ (15)

[NH3]total

[NH3]total = [NH3] + [NH4+]

= A (16)

(15) (16)

pH + pNH3

= pKa – log [NH3]total + log (1 + 10pH – pKa)

= pKa – log A + log (1 + 10pH – pKa) (17)

pH pKa pH

pH + pNH3 = pKa – log A

pH << pKa (18-1)

pNH3 = – log A pH >> pKa (18-2)

pKa = 9.3

pH + pNH3 = 9.3 – log A

pH < 8.3 (19-1)

pNH3 = – log A pH > 10.3 (19-2)

pKa = 9.3

(17) pH = 8.3 10.3

pH < 8.3 pH >

10.3 ABCD

A = [NH3]total = 5.0 mol dm–3

(15) (16)

pH pNH3

pNH3 pH

41


ABCD

ABCD

pH

Cd(NH3)42+

Cd pH = 9.3

ABCD

Cd(NH3)42+

Cd pH = 9.3 = pKa

pH pKa

pH pH < 8.3 (1)

Cd(NH3)42+

+ 4H+ + 2e

= Cd + 4NH4+ (20)

H+

pH

pH

pH = pKa pH

pH > 10.3 (1)

Cd(NH3)42+

+ 2e = Cd + 4NH3 (21)

pH

pKa

8.3 < pH < 10.3 (20) (21)

Cd(NH3)42+

Cd2+

Cd(OH)2

pH

pKa

(1)

NH3 aNH3

Cd(NH3)42+

Cd2+

Cd(NH3)42+

Cd2+

+ 4NH4+ = Cd(NH3)4

2+ + 4H

+ (22)

pH

OH–

Cd(NH3)42+

Cd(OH)2 Cd(NH3)42+

Cd(OH)2

Cd(NH3)42+

+ 2H2O

= Cd(OH)2 + 2H+ + 4NH3 (23)

Cd(NH3)42+

pKa pH

(20) (23)

pH

A = [NH3]total = 5.0 mol dm–3

1.0 mol dm–3

0.5 mol dm–3

pKa

= 9.3 (19-1)

(19-2) A

ABCD pNH3

Cd(NH3)42+

ABCD

Cd(NH3)42+

pH

A (22)

(23)

(22)

Cd2+

+ 2H2O = Cd(OH)2 + 2H+ (24)

pH

A

(22) pH

(24) pH

42


Cd2+

Cd(NH3)42+

Cd(OH)2

(22) (24)

pH pH

pH Cd2+

Cd(NH3)42+

pH pH

Cd2+

Cd(NH3)42+

Cd(OH)2

Cd(NH3)42+

pH Cd(OH)2

(23) pH Cd(OH)2

Cd(NH3)42+

+ 2H2O + 2H+

= Cd(OH)2 + 4NH4+ (25)

NH4+

A

(23) (25) pH

Cd(NH3)42+

Cd-H2O pH

(23)

(25) pH

Cd(NH3)42+

Koyama Cu-NH3-H2O

pH9)

Cu2O Cu(OH)2

pKa = 9.3 pH

Cu(NH3)2+

Cu(NH3)42+

pH

pKa NH4+

pH pKa

NH3

pH

Cu-NH3-H2O pH

25 °C aCu(II) = aCu(I) = 0.5 [NH3]total = [NH3]

+ [NH4+] = 7.0 mol dm

–3 9)

pH

pH

CuFeS2

10)

CdTe

Cd-Te-H2O

Cd-Te-NH3-H2O

pH

GaAs InAs

pH

Montana Tech

Hsin-Hsiung Huang

STABCAL

Cd-Te-NH3-H2O8,11)

pH

43


(a) Cd-Te-H2O (b)

Cd-Te-NH3-H2O pH

25 °C aCd = 0.01 aTe = 0.01 pH2Te = 1 atm

[NH3]total = [NH3] + [NH4+] = 5.0 mol dm

–3

Cd-Te-NH3-H2O pH

Te-H2O

Cd-NH3-H2O pH

pH

CdTe

TeO32–

Cd(NH3)42+

CdTe

Cd(NH3)42+

TeO32–

CdTe

H2O

Ga-As-H2O In-As-H2O

pH 25 °C aGa =

1 aIn = 1 aAs = 1 GaAs

InAs

Te-H2O pH 25 °C

aTe = 0.01 pH2Te = 1 atm

44


Te-H2O Cd-NH3-H2O

pH

H+

e

pH >

pKa = 9.3 NH3

Cd(NH3)42+

+ TeO32–

+ 6H+ + 6e

= CdTe + 3H2O + 4NH3 (26)

Nernst

pH

ECd(NH3)42+,TeO3

2– CdTe

(26)

CdTe

CdTe

CdTe

CdTe

CdTe

CdTe + 2e = Cd + Te2–

(27)

CdTe

Cd-Te-NH3-H2O

pH Cd-NH3-H2O

-pH

CdTe

Cd

CdTe Cd

Cd Cd

pH = 10.5

Cd(NH3)42+

+ 2e = Cd + 4NH3 (21)

Cd(NH3)42+

+ Te + 2e

= CdTe + 4NH3 (28)

(28) 0.516 V

(28) (21)

Cd + Te = CdTe (29)

ΔE = 0.516 V CdTe

ΔE CdTe

ΔG° = –99.57 kJ mol–1

ΔE =

–ΔG° nF n

2 F

pH

11,12)

11,13)

pH ZnTe

Zn-Te-NH3-H2O

pH14)

45


pH

Mn+

+ ne = M (30)

Nernst

(31)

Mn+

Mn+

aMn+ (31)

aMn+

EMn+ M M

M aM

EMn+ M

pH

(30)

pH

pH

1) G. Charlot , , ,

,

, 1958.

2) M. Pourbaix, “Atlas of Electrochemical

Equilibria in Aqueous Solutions”, Per-

gamon Press, Oxford, 1966.

3) , ,

-pH (III), , 29, 385

(1959).

4) , -pH

, ,

27, 365 (1959).

5) ,

, 36

p. 73,

, 2009.

6) T. D. Golden, M. G. Shumsky, Y. Zhou, R.

A. VanderWerf, R. A. Van Leeuwen, and

J. A. Switzer, Electrochemical deposition

of copper(I) oxide films, Chem. Mater., 8,

2499 (1996); K. Mizuno, M. Izaki, K.

Murase, T. Shinagawa, M. Chigane, M.

Inaba, A. Tasaka, and Y. Awakura, Struc-

tural and electrical characterizations of

electrodeposited p-type semiconductor

Cu2O films, J. Electrochem. Soc., 152,

C179 (2005).

7) , , ,

, , , (I)

, , 121, 103 (2005);

, , , ,

(I)

, ,

122, 21 (2006).

8) K. Murase, H. Watanabe, T. Hirato, and Y.

Awakura, Potential pH diagram of the

Cd-Te-NH3-H2O system and electro-

deposition behavior of CdTe from am-

moniacal alkaline baths, J. Electrochem.

Soc., 146, 1798 (1999).

9) K. Koyama, M. Tanaka, and J.-c. Lee,

Copper leaching behavior from waste

46


printed circuit board in ammoniacal alka-

line solution, Mater. Trans., 47, 1788

(2006).

10) E. Peters, Direct leaching of sulfides:

Chemistry and applications, Metall.

Trans. B, 7, 505 (1976).

11) , , -pH

CdTe

, , 55, 903

(2004).

12) K. Murase, T. Honda, M. Yamamoto, T.

Hirato, and Y. Awakura, Electrodeposi-

tion of CdTe from basic aqueous solu-

tions containing ethylenediamine, J.

Electrochem. Soc., 148, C203 (2001).

13) , , ,

,

CdTe ,

, 53, 535 (2002).

14) K. Murase, T. Suzuki, Y. Umenaka, T.

Hirato, and Y. Awakura, Thermodynamics

of cathodic ZnTe electrodeposition using

basic ammoniacal electrolytes: Why

CdTe can deposit while ZnTe cannot,

High Temp. Mater. Process., 30, 451

(2011).

43

47


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