P2: Standard Reduction Potentials by Value

The following table provides E^o for selected reduction reactions. Values are from the following sources: Bard, A. J.; Parsons, B.; Jordon, J., eds. Standard Potentials in Aqueous Solutions, Dekker: New York, 1985; Milazzo, G.; Caroli, S.; Sharma, V. K. Tables of Standard Electrode Potentials, Wiley: London, 1978; Swift, E. H.; Butler, E. A. Quantitative Measurements and Chemical Equilibria, Freeman: New York, 1972.

The table is ordered such that the stronger (more reactive) reductants are at the top and the stronger oxidants are at the bottom.

Standard Cathode (Reduction) Half-Reaction	Standard Reduction Potential E° (volts)
Li^+(aq) + e^- $\rightleftharpoons$ Li(s)	-3.040
Rb^+ + e^- $\rightleftharpoons$ Rb (s)	-2.98
K^+(aq) + e^- $\rightleftharpoons$ K(s)	-2.93
Ba^2^+ + 2e^−$\rightleftharpoons$ Ba(s)	-2.92
Cs^+(aq) + e^- $\rightleftharpoons$ Cs(s)	-2.92
Ba^2^+(aq) + 2e- $\rightleftharpoons$ Ba(s)	-2.91
Sr^2^+(aq) + 2e- $\rightleftharpoons$ Sr(s)	-2.89
Ca^2^+(aq) + 2e- $\rightleftharpoons$ Ca(s)	-2.84
Na^+(aq) + e^- $\rightleftharpoons$ Na(s)	-2.713
Mg(OH)2(s) + 2e^−$\rightleftharpoons$ Mg(s) + 2OH^−	-2.687
La^3^+ + 3e^−$\rightleftharpoons$ La(s)	-2.38
Mg^2^+(aq) + 2e^- $\rightleftharpoons$ Mg(s)	-2.356
Ce^3^+ + 3e^−$\rightleftharpoons$ Ce(s)	-2.336
Al(OH)4^− + 3e^−$\rightleftharpoons$ Al(s) + 4OH^−	-2.310
BaO(s) + 2H^+ + 2e^– $\rightleftharpoons$ Ba(s) + H2O(l)	-2.166
AlF6^3^− + 3e^−$\rightleftharpoons$ Al(s) + 6F^−	-2.07
Be^2^+ + 2e^−$\rightleftharpoons$ Be(s)	-1.99
B(OH)4^− + 3e^−$\rightleftharpoons$ B(s) + 4OH^−	-1.811
Al^3^+(aq) + 3e^- $\rightleftharpoons$ Al(s)	-1.676
U^3^+ + 3e^−$\rightleftharpoons$ U(s)	-1.66
ZnO2 + 4H^++ 4e^− $\rightleftharpoons$ Zn(s) + 2H2O	-1.473
SiF6^2^− + 4e^−$\rightleftharpoons$ Si(s) + 6F^−	-1.37
Zn(CN)4^2− + 2e^−$\rightleftharpoons$ Zn(s) + 4CN	-1.34
Zn(OH)4^2− + 2e^−$\rightleftharpoons$ Zn(s) + 4OH^−	-1.285
Mn^2^+ + 2e^−$\rightleftharpoons$ Mn(s)	-1.17
CdS(s) +  2e^−$\rightleftharpoons$ Cd(s) + S^2−	-1.17
V^2^+ + 2e^−$\rightleftharpoons$ V(s)	-1.13
2SO3^2^− + 2H2O(l) + 2e^−$\rightleftharpoons$ S2O4^2^− + 4OH^−	-1.13
Zn(NH3)4^2+ + 2e^−$\rightleftharpoons$ Zn(s) + 4NH3	-1.04
O2 (aq) + e^- $\rightleftharpoons$ O2^-(aq)	-1.0
Cd(CN)4^2− + 2e^−$\rightleftharpoons$ Cd(s) + 4CN^−	-0.943
MoO4^2^− + 4H2O(l) + 6e^−$\rightleftharpoons$Mo(s) + 8OH^−	-0.913
SO4^2^− + H2O(l) + 2e^− $\rightleftharpoons$ SO3^2^−+ 2OH^−	-0.936
SiO2(s) + 4H^+ + 4e^−$\rightleftharpoons$ Si(s) + 2H2O(l)	-0.909
Cr^2^+ + 2e^−$\rightleftharpoons$ Cr(s)	-0.90
B(OH)3 + 3H^+ + 3e^−$\rightleftharpoons$ B(s) + 3H2O(l)	-0.890
2H2O(l) + 2e^- $\rightleftharpoons$ H2(g) + 2OH^-(aq)	-0.828
Zn^2^+(aq) + 2e^- $\rightleftharpoons$ Zn(s)	-0.7618
Co(OH)2(s) + 2e^−$\rightleftharpoons$ Co(s) + 2OH^−	-0.746
Cr^3^+(aq) + 3e^- $\rightleftharpoons$ Cr(s)	-0.74
Ni(OH)2 + 2e^−$\rightleftharpoons$ Ni(s) + 2OH^−	-0.72
Ag2S(s) + 2e^−$\rightleftharpoons$ 2Ag(s) + S^2−	-0.71
Se(s) + 2e^−$\rightleftharpoons$ Se^2^−	-0.67 in 1 M NaOH
Cd(NH3)4^2+ + 2e^−$\rightleftharpoons$ Cd(s) + 4NH3	-0.622
2SO3^2^− + 3H2O(l) + 4e^−$\rightleftharpoons$S2O3^2^− + 6OH^−	-0.576 in 1 M NaOH
Ga^3^+ + 3e^−$\rightleftharpoons$ Ga(s)	-0.56
U^4^+ + e^−$\rightleftharpoons$ U^3^+	-0.52
SiO2(s) + 8H^+ + 8e^−$\rightleftharpoons$ SiH4(g) + 2H2O(l)	-0.516
Sb + 3H^+ + 3e^−$\rightleftharpoons$ SbH3(g)	-0.510
H3PO3+ 2H^+ + 2e^−$\rightleftharpoons$ H3PO2 + H2O(l)	-0.50
Ni(NH3)6^2+ + 2e^−$\rightleftharpoons$ Ni(s) + 6NH3	-0.49
2CO2(g) + 2H^+ +2e^−$\rightleftharpoons$ H2C2O4	-0.481
Cr^3^+ + e^−$\rightleftharpoons$ Cr^2^+	-0.424
Fe^2^+(aq) + 2e^- $\rightleftharpoons$ Fe(s)	-0.44
S(s) + 2e^−$\rightleftharpoons$ S^2−	-0.407
Cd^2^+(aq) + 2e^- $\rightleftharpoons$ Cd(s)	-0.4030
Ag(NH3)2^+ + e^−$\rightleftharpoons$ Ag(s) + 2NH3	-0.373
Ti^3^+ + e^−$\rightleftharpoons$ Ti^2^+	-0.37
PbSO4(s) + 2e^−$\rightleftharpoons$ Pb(s) + SO4^2^−	-0.356
Co^2^+(aq) + 2e^- $\rightleftharpoons$ Co(s)	-0.277
2SO4^2^− + 4H^+ + 2e^−$\rightleftharpoons$ S2O6^2^− + 2H2O(l)	-0.25
N2(g) + 5H^+ + 4e^−$\rightleftharpoons$ N2H5^+	-0.23
H3PO4 + 2H^+ + 2e^−$\rightleftharpoons$ H3PO3 + H2O(l)	-0.28
Ni^2^+(aq) + 2e^- $\rightleftharpoons$ Ni(s)	-0.257
V^3^+ + e^−$\rightleftharpoons$ V^2^+	-0.255
As + 3H^+ + 3e^−$\rightleftharpoons$ AsH3(g)	-0.225
CO2(g) + 2H^+ + 2e^−$\rightleftharpoons$ HCO2H	-0.20
Mo^3^+ + 3e^−$\rightleftharpoons$ Mo(s)	-0.2
Ti^2^+ + 2e^−$\rightleftharpoons$ Ti(s)	-0.163
MoO2(s) + 4H^+ + 4e^−$\rightleftharpoons$ Mo(s) + 2H2O(l)	-0.152
AgI(s) + e^−$\rightleftharpoons$ Ag(s) + I^−	-0.152
Sn^2^+(aq) + 2e^- $\rightleftharpoons$ Sn(s)	-0.136
CrO4^2^− + 4H2O(l) + 3e^−$\rightleftharpoons$2Cr(OH)4^− + 4OH^−	-0.13 in 1 M NaOH
Pb^2^+(aq) + 2e^- $\rightleftharpoons$ Pb(s)	-0.126
WO2(s) + 4H^+ + 4e^−$\rightleftharpoons$ W(s) + 2H2O(l)	-0.119
Se(s) + 2H^+ + 2e^−$\rightleftharpoons$ H2Se(g)	-0.115
CO2(g) + 2H^+ + 2e^−$\rightleftharpoons$ CO(g) + H2O(l)	-0.106
WO3(s) + 6H^+ + 6e^−$\rightleftharpoons$ W(s) + 3H2O(l)	-0.090
Hg2I2(s) + 2e^−$\rightleftharpoons$ 2Hg(l) + 2I^−	-0.0405
Fe^3^+(aq) + 3e^- $\rightleftharpoons$ Fe(s)	-0.037
2H^+(aq) + 2e^- $\rightleftharpoons$ H2(g)	0.00
P(s,white) + 3H^+ + 3e^−$\rightleftharpoons$ PH3(g)	0.06
AgBr(s) + e^−$\rightleftharpoons$ Ag(s) + Br^−	0.071
S4O6^2^− + 2e^−$\rightleftharpoons$2S2O3^2^−	0.080
Co(NH3)6^3+ +e^−$\rightleftharpoons$Co(NH3)6^2+	0.1
Ru(NH3)6^3+ + e^−$\rightleftharpoons$ Ru(s) + Ru(NH3)6^2+	0.10
S(s) + 2H^+ + 2e^−$\rightleftharpoons$ H2S	0.144
Sn^4^+(aq) + 2e^- $\rightleftharpoons$ Sn^2^+(aq)	0.154
Cu^2^+(aq) + e^- $\rightleftharpoons$ Cu^+(aq)	0.159
UO2^2^+ + e^−$\rightleftharpoons$UO2^+	0.16
Co(OH)3(s) + e^−$\rightleftharpoons$ Co(OH)2(s) + OH^−	0.17
ClO4^-(aq) + H2O(l) + 2e- $\rightleftharpoons$ ClO3^-(aq) + 2OH^-(aq)	0.17
SO4^2^− + 4H^+ + 2e^−$\rightleftharpoons$ H2SO3 (aq) + H2O(l)	0.172
BiCl4^− + 3e^−$\rightleftharpoons$ Bi(s) + 4Cl^−	0.199
SbO^++ 2H^+ + 3e^−$\rightleftharpoons$ Sb(s) + H2O(l)	0.212
AgCl(s) + e^- $\rightleftharpoons$ Ag(s) + Cl^-(aq)	0.2223
HCHO + 2H^+ + 2e^−$\rightleftharpoons$ CH3OH	0.2323
HAsO2 + 3H^+ + 3e^−$\rightleftharpoons$ As(s) + 2H2O(l)	0.240
Ru^3^+ + e^−$\rightleftharpoons$ Ru^2^+	0.249
IO3^−+ 3H2O(l) + 6e^−$\rightleftharpoons$ I^− + 6OH^−	0.257
Hg2Cl2(s) + 2e^−$\rightleftharpoons$ 2Hg(l) + 2Cl^−	0.2682
UO2^+ + 4H^+ + e^−$\rightleftharpoons$U^4^+ + 2H2O(l)	0.27
Bi^3^+ + 3e^−$\rightleftharpoons$ Bi(s)	0.317
UO2^2^+ + 4H^+ + 2e^−$\rightleftharpoons$ U^4^+ + 2H2O(l)	0.327
VO^2^+ + 2H^+ +e^−$\rightleftharpoons$V^3^+ + H2O(l)	0.337
Cu^2^+(aq) + 2e^- $\rightleftharpoons$ Cu(s)	0.3419
ClO3^-(aq) + H2O(l) + 2e^- $\rightleftharpoons$ ClO2^-(aq) + 2OH^-(aq)	0.35
Fe(CN)6^3− + e^−$\rightleftharpoons$ Fe(CN)6^4−	0.356
O2(g) + 2H2O(l) + 4e^−$\rightleftharpoons$ 4OH^−	0.401
ClO^− + H2O(l) + e^−$\rightleftharpoons$ ½Cl2(g) + 2OH^−	0.421 in 1 M NaOH
Ag2C2O4(s) + 2e^−$\rightleftharpoons$ 2Ag(s) + C2O4^2^−	0.47
Cu^+(aq) + e^- $\rightleftharpoons$ Cu(s)	0.52
I2(s) + 2e^- $\rightleftharpoons$ 2I^-(aq)	0.5355
I3^− + 2e^−$\rightleftharpoons$ 3I^−	0.536
Cu^2^+ + Cl^− + e^−$\rightleftharpoons$ CuCl(s)	0.559
H3AsO4 + 2H^+ + 2e^−$\rightleftharpoons$ HAsO2 + 2H2O(l)	0.560
S2O6^2^− + 4H^+ + 2e^−$\rightleftharpoons$ 2H2SO3	0.569
ClO2^-(aq) + H2O(l) + 2e^- $\rightleftharpoons$ ClO^-(aq) + 2OH^-(aq)	0.59
MnO4^− + 2H2O(l) + 3e^−$\rightleftharpoons$ MnO2(s) + 4OH^−	0.60
Sb2O5(s) + 6H^+ + 4e^−$\rightleftharpoons$ 2SbO^+ + 3H2O(l)	0.605
PtCl6^2^− + 2e^−$\rightleftharpoons$ PtCl4^2^- + 2Cl^−	0.68
RuO2(s) + 4H^+ + 4e^−$\rightleftharpoons$ Ru(s) + 2H2O(l)	0.68
O2(g) + 2H^+ + 2e^−$\rightleftharpoons$ H2O2	0.695
PtCl4^2^− + 2e^−$\rightleftharpoons$ Pt(s) + 4Cl^−	0.73
H2SeO3 + 4H^+ + 4e^−$\rightleftharpoons$ Se(s) + 3H2O(l)	0.74
Tl^3^+ + 3e^−$\rightleftharpoons$ Tl(s)	0.742
Tl^3^+ + 2e^−$\rightleftharpoons$ Tl^+	0.77 in 1 M HCl
Fe^3^+(aq) + e^- $\rightleftharpoons$ Fe^2^+(aq)	0.771
Hg2^2^+(aq) + 2e^- $\rightleftharpoons$ 2Hg(l)	0.7960
Ag^+(aq) + e- $\rightleftharpoons$ Ag(s)	0.7996
Hg^2^+(aq) + 2e^- $\rightleftharpoons$ Hg(l)	0.8535
Cu^2^+ + I^− +e^−$\rightleftharpoons$ CuI(s)	0.86
Ru(CN)6^3− +e^−$\rightleftharpoons$ Ru(s) + Ru(CN)6^4−	0.86
ClO^− + H2O(l) + 2e^−$\rightleftharpoons$ Cl^− + 2OH^−	0.890 in 1 M NaOH
2Hg^2^+(aq) + 2e^- $\rightleftharpoons$ Hg2^2^+(aq)	0.911
HgO(s) + 2H^+ + 2e^−$\rightleftharpoons$ Hg(l) + H2O(l)	0.926
NO3^− + 3H^+ + 2e^−$\rightleftharpoons$ HNO2 + H2O(l)	0.94
MnO2(s) + 4H^+ + e^- $\rightleftharpoons$ Mn^3^+ (aq) + 2H2O(l)	0.95
NO3^-(aq) + 4H^+(aq) + 3e^- $\rightleftharpoons$ NO(g) + 2H2O(l)	0.96
HIO + H^+ + 2e^−$\rightleftharpoons$ I^− + H2O(l)	0.985
HNO2 + H^+ +e^−$\rightleftharpoons$ NO(g) + H2O(l)	0.996
VO2^2^+ + 2H^+ +e^−$\rightleftharpoons$ VO^2^+ + H2O(l)	1.000
AuCl4^− + 3e^−$\rightleftharpoons$ Au(s) + 4Cl^−	1.002
NO2 (g) + H^+ (aq) + e^- $\rightleftharpoons$ HNO2 (aq)	1.07
Br2(l) + 2e^- $\rightleftharpoons$ 2Br^-(aq)	1.087
Fe(phen)6^3+ +e^−$\rightleftharpoons$ Fe(phen)6^2+	1.147
SeO4^3^− + 4H^+ + e^−$\rightleftharpoons$ H2SeO3 + H2O(l)	1.151
ClO3^− + 2H^+ + e^−$\rightleftharpoons$ ClO2(g) + H2O	1.175
ClO3^− + 3H^+ + 2e^−$\rightleftharpoons$ HClO2 + H2O	1.181
IO3^− + 6H^+ + 5e^−$\rightleftharpoons$ ½I2(s) + 3H2O(l)	1.195
Pt^2^+ + 2e^−$\rightleftharpoons$ Pt(s)	1.2
ClO4^− + 2H^+ + 2e^−$\rightleftharpoons$ ClO3^− + H2O	1.201
O2(g) + 4H^+(aq) + 4e^- $\rightleftharpoons$ 2H2O(l)	1.229
MnO2(s) + 4H^+ + 2e^−$\rightleftharpoons$ Mn^2^+ + 2H2O(l)	1.23
2HNO2 + 4H^+ + 4e^−$\rightleftharpoons$ N2O(g) + 3H2O(l)	1.297
HOBr + H^+ + 2e^−$\rightleftharpoons$ Br^− + H2O(l)	1.341
Cr2O7^2^-(aq) + 14H^+(aq) + 6e^- $\rightleftharpoons$ 2Cr^3^+(aq) + 7H2O(l)	1.36
Au^3^+ + 2e^−$\rightleftharpoons$ Au^+	1.36
Hg2Br2(s) + 2e^−$\rightleftharpoons$ 2Hg(l) + 2Br^−	1.392
Cl2(g) + 2e^- $\rightleftharpoons$ 2Cl^-(aq)	1.396
Hg2Br2(s) + 2e^−$\rightleftharpoons$ 2Hg(l) + 2Br^−	1.392
Ce^4^+(aq) + e^- $\rightleftharpoons$ Ce^3^+(aq)	1.44
PbO2(s) + 4H^+ +2e^- $\rightleftharpoons$ Pb^2^+(aq) + 2H2O(l)	1.46
BrO3^− + 6H^+ + 6e^−$\rightleftharpoons$ Br^− + 3H2O	1.478
Mn^3^+ + e^−$\rightleftharpoons$ Mn^2^+	1.5
BrO3^− + 6H^+ + 5e^−$\rightleftharpoons$ ½Br2(l) + 3H2O	1.5
MnO4^-(aq) + 8H^+(aq) + 5e^- $\rightleftharpoons$ Mn^2^+(aq) + 4H2O(l)	1.51
Au^3^+ + 3e^−$\rightleftharpoons$ Au(s)	1.52
2NO(g) + 2H^+ + 2e^−$\rightleftharpoons$ N2O(g) + H2O(l)	1.59
HOBr + H^+ + e^−$\rightleftharpoons$ ½Br^− + H2O(l)	1.604
HClO2 + 2H^+ + 2e^−$\rightleftharpoons$ HOCl + H2O	1.64
PbO2(s) + SO4^2^− + 4H^+ + 2e^−$\rightleftharpoons$ PbSO4(s) + 2H2O(l)	1.690
MnO4^− + 4H^+ +3e^−$\rightleftharpoons$ MnO2(s) + 2H2O(l)	1.70
Ce^4^+ + e^−$\rightleftharpoons$ Ce^3^+	1.72
N2O(g) + 2H^+ + 2e^−$\rightleftharpoons$ N2(g) + H2O(l)	1.77
H2O2(aq) + 2H^+(aq) + 2e^- $\rightleftharpoons$ 2H2O(l)	1.763
Au^+ + e^−$\rightleftharpoons$ Au(s)	1.83
Co^3^+(aq) + e^- $\rightleftharpoons$ Co^2^+(aq)	1.92
S2O8^2^− + 2e^−$\rightleftharpoons$2SO4^2^−	1.96
O3(g) + 2H^+(aq) + 2e^- $\rightleftharpoons$ O2(g) + H2O(l)	2.07
F2(g) + 2e^- $\rightleftharpoons$ 2F^-(aq)	2.87
F2(g) + 2H^+ + 2e^−$\rightleftharpoons$ 2HF	3.053

Contributors and Attributions

• David Harvey (DePauw University)