Standard Reduction Potentials

The values of standard electrode potentials are given in the table below in volts relative to the standard hydrogen electrode and are assembled from references

The values are for the following conditions:



* the temperature of 298.15 K (25 °C);
* the effective concentration of 1 mol/L for each aqueous species or a species in a mercury amalgam;
* the partial pressure of 101.325 kPa (absolute) (1 atm, 1.01325 bar) for each gaseous reagent. This pressure is used because most literature data are still given for this value rather than for the current standard of 100 kPa.
* the activity of unity for each pure solid, pure liquid, or for water (solvent).

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Legend: (s) – solid; (l) – liquid; (g) – gas; (aq) – aqueous (default for all charged species); (Hg) – amalgam.
Half-reaction E° (V)
& -9
Zz 9
\tfrac{3}{2} N2(g) + H+ + e− ⇄ HN3(aq) −3.09
Li+ + e− ⇄ Li(s) −3.0401
N2(g) + 4 H2O + 2 e− ⇄ 2 NH2OH(aq) + 2 OH− −3.04
Cs+ + e− ⇄ Cs(s) −3.026
Rb+ + e− ⇄ Rb(s) −2.98
K+ + e− ⇄ K(s) −2.931
Ba2+ + 2 e− ⇄ Ba(s) −2.912
La(OH)3(s) + 3 e− ⇄ La(s) + 3OH− −2.90
Sr2+ + 2 e− ⇄ Sr(s) −2.899
Ca2+ + 2 e− ⇄ Ca(s) −2.868
Eu2+ + 2 e− ⇄ Eu(s) −2.812
Ra2+ + 2 e− ⇄ Ra(s) −2.8
Na+ + e− ⇄ Na(s) −2.71
La3+ + 3 e− ⇄ La(s) −2.379
Y3+ + 3 e− ⇄ Y(s) −2.372
Mg2+ + 2 e− ⇄ Mg(s) −2.372
ZrO(OH)2(s) + H2O + 4 e− ⇄ Zr(s) + 4OH− −2.36
Al(OH)4− + 3 e− ⇄ Al(s) + 4 OH− −2.33
Al(OH)3(s) + 3 e− ⇄ Al(s) + 3OH− −2.31
H2(g) + 2 e− ⇄ 2 H− −2.25
Ac3+ + 3 e− ⇄ Ac(s) −2.20
Be2+ + 2 e− ⇄ Be(s) −1.85
U3+ + 3 e− ⇄ U(s) −1.66
Al3+ + 3 e− ⇄ Al(s) −1.66
Ti2+ + 2 e− ⇄ Ti(s) −1.63
ZrO2(s) + 4 H+ + 4 e− ⇄ Zr(s) + 2 H2O −1.553
Zr4+ + 4 e− ⇄ Zr(s) −1.45
TiO(s) + 2 H+ + 2 e− ⇄ Ti(s) + H2O −1.31
Zn(OH)42− + 2 e− ⇄ Zn(s) + 4OH- −1.199
Ti2O3(s) + 2 H+ + 2 e− ⇄ 2 TiO(s) + H2O −1.23
Ti3+ + 3 e− ⇄ Ti(s) −1.21
Mn2+ + 2 e− ⇄ Mn(s) −1.185
Te(s) + 2 e− ⇄ Te2− −1.143
V2+ + 2 e− ⇄ V(s) −1.13
Nb3+ + 3 e− ⇄ Nb(s) −1.099
Sn(s) + 4 H+ + 4 e− ⇄ SnH4(g) −1.07
SiO2(s) + 4 H+ + 4 e− ⇄ Si(s) + 2 H2O −0.91
B(OH)3(aq) + 3 H+ + 3 e− ⇄ B(s) + 3 H2O −0.89
TiO2+ + 2 H+ + 4 e− ⇄ Ti(s) + H2O −0.86
Bi(s) + 3 H+ + 3 e− ⇄ BiH3 −0.8
2 H2O + 2 e− ⇄ H2(g) + 2 OH− −0.8277
Zn2+ + 2 e− ⇄ Zn(Hg) −0.7628
Zn2+ + 2 e− ⇄ Zn(s) −0.7618
Ta2O5(s) + 10 H+ + 10 e− ⇄ 2 Ta(s) + 5 H2O −0.75
Cr3+ + 3 e− ⇄ Cr(s) −0.74
[Au(CN)2]− + e− ⇄ Au(s) + 2 CN− −0.60
Ta3+ + 3 e− ⇄ Ta(s) −0.6
PbO(s) + H2O + 2 e− ⇄ Pb(s) + 2 OH− −0.58
2 TiO2(s) + 2 H+ + 2 e− ⇄ Ti2O3(s) + H2O −0.56
Ga3+ + 3 e− ⇄ Ga(s) −0.53
AgI(s) + e− ⇄ Ag(s) + I− −0.15224
U4+ + e− ⇄ U3+ −0.52
H3PO2(aq) + H+ + e− ⇄ P(white[note 1]) + 2 H2O −0.508
H3PO3(aq) + 2 H+ + 2 e− ⇄ H3PO2(aq) + H2O −0.499
H3PO3(aq) + 3 H+ + 3 e− ⇄ P(red)[note 1] + 3H2O −0.454
Fe2+ + 2 e− ⇄ Fe(s) −0.44
2 CO2(g) + 2 H+ + 2 e− ⇄ HOOCCOOH(aq) −0.43
Cr3+ + e− ⇄ Cr2+ −0.42
Cd2+ + 2 e− ⇄ Cd(s) −0.40
GeO2(s) + 2 H+ + 2 e− ⇄ GeO(s) + H2O −0.37
Cu2O(s) + H2O + 2 e− ⇄ 2 Cu(s) + 2 OH− −0.360
PbSO4(s) + 2 e− ⇄ Pb(s) + SO42− −0.3588
PbSO4(s) + 2 e− ⇄ Pb(Hg) + SO42− −0.3505
Eu3+ + e− ⇄ Eu2+ −0.35
In3+ + 3 e− ⇄ In(s) −0.34
Tl+ + e− ⇄ Tl(s) −0.34
Ge(s) + 4 H+ + 4 e− ⇄ GeH4(g) −0.29
Co2+ + 2 e− ⇄ Co(s) −0.28
H3PO4(aq) + 2 H+ + 2 e− ⇄ H3PO3(aq) + H2O −0.276
V3+ + e− ⇄ V2+ −0.26
Ni2+ + 2 e− ⇄ Ni(s) −0.25
As(s) + 3 H+ + 3 e− ⇄ AsH3(g) −0.23
MoO2(s) + 4 H+ + 4 e− ⇄ Mo(s) + 2 H2O −0.15
Si(s) + 4 H+ + 4 e− ⇄ SiH4(g) −0.14
Sn2+ + 2 e− ⇄ Sn(s) −0.13
O2(g) + H+ + e− ⇄ HO2•(aq) −0.13
Pb2+ + 2 e− ⇄ Pb(s) −0.13
WO2(s) + 4 H+ + 4 e− ⇄ W(s) + 2 H2O −0.12
P(red) + 3 H+ + 3 e− ⇄ PH3(g) −0.111
CO2(g) + 2 H+ + 2 e− ⇄ HCOOH(aq) −0.11
Se(s) + 2 H+ + 2 e− ⇄ H2Se(g) −0.11
CO2(g) + 2 H+ + 2 e− ⇄ CO(g) + H2O −0.11
SnO(s) + 2 H+ + 2 e− ⇄ Sn(s) + H2O −0.10
SnO2(s) + 2 H+ + 2 e− ⇄ SnO(s) + H2O −0.09
WO3(aq) + 6 H+ + 6 e− ⇄ W(s) + 3 H2O −0.09
P(white) + 3 H+ + 3 e− ⇄ PH3(g) −0.063
HCOOH(aq) + 2 H+ + 2 e− ⇄ HCHO(aq) + H2O −0.03
2 H+ + 2 e− ⇄ H2(g) 0.0000 ≡ 0
AgBr(s) + e− ⇄ Ag(s) + Br− +0.07133
S4O62− + 2 e− ⇄ 2 S2O32− +0.08
Fe3O4(s) + 8 H+ + 8 e− ⇄ 3 Fe(s) + 4 H2O +0.085
N2(g) + 2 H2O + 6H+ + 6 e− ⇄ 2 NH4OH(aq) +0.092
HgO(s) + H2O + 2 e− ⇄ Hg(l) + 2 OH− +0.0977
Cu(NH3)42+ + e− ⇄ Cu(NH3)2+ + 2 NH3 +0.10
Ru(NH3)63+ + e− ⇄ Ru(NH3)62+ +0.10
N2H4(aq) + 4 H2O + 2 e− ⇄ 2 NH4+ + 4 OH− +0.11
H2MoO4(aq) + 6 H+ + 6 e− ⇄ Mo(s) + 4 H2O +0.11
Ge4+ + 4 e− ⇄ Ge(s) +0.12
C(s) + 4 H+ + 4 e− ⇄ CH4(g) +0.13
HCHO(aq) + 2 H+ + 2 e− ⇄ CH3OH(aq) +0.13
S(s) + 2 H+ + 2 e− ⇄ H2S(g) +0.14
Sn4+ + 2 e− ⇄ Sn2+ +0.15
Cu2+ + e− ⇄ Cu+ +0.159
HSO4− + 3 H+ + 2 e− ⇄ SO2(aq) + 2 H2O +0.16
UO22+ + e− ⇄ UO2+ +0.163
SO42− + 4 H+ + 2 e− ⇄ SO2(aq) + 2 H2O +0.17
TiO2+ + 2 H+ + e− ⇄ Ti3+ + H2O +0.19
SbO+ + 2 H+ + 3 e− ⇄ Sb(s) + H2O +0.20
AgCl(s) + e− ⇄ Ag(s) + Cl− +0.22233
H3AsO3(aq) + 3 H+ + 3 e− ⇄ As(s) + 3 H2O +0.24
GeO(s) + 2 H+ + 2 e− ⇄ Ge(s) + H2O +0.26
UO2+ + 4 H+ + e− ⇄ U4+ + 2 H2O +0.273
Re3+ + 3 e− ⇄ Re(s) +0.300
Bi3+ + 3 e− ⇄ Bi(s) +0.308
VO2+ + 2 H+ + e− ⇄ V3+ + H2O +0.34
Cu2+ + 2 e− ⇄ Cu(s) +0.340
[Fe(CN)6]3− + e− ⇄ [Fe(CN)6]4− +0.36
O2(g) + 2 H2O + 4 e− ⇄ 4 OH−(aq) +0.40
H2MoO4 + 6 H+ + 3 e− ⇄ Mo3+ + 2 H2O +0.43
CH3OH(aq) + 2 H+ + 2 e− ⇄ CH4(g) + H2O +0.50
SO2(aq) + 4 H+ + 4 e− ⇄ S(s) + 2 H2O +0.50
Cu+ + e− ⇄ Cu(s) +0.520
CO(g) + 2 H+ + 2 e− ⇄ C(s) + H2O +0.52
I2(s) + 2 e− ⇄ 2 I− +0.54
I3− + 2 e− ⇄ 3 I− +0.53
[AuI4]− + 3 e− ⇄ Au(s) + 4 I− +0.56
H3AsO4(aq) + 2 H+ + 2 e− ⇄ H3AsO3(aq) + H2O +0.56
[AuI2]− + e− ⇄ Au(s) + 2 I− +0.58
MnO4− + 2 H2O + 3 e− ⇄ MnO2(s) + 4 OH− +0.59
S2O32 − + 6 H+ + 4 e− ⇄ 2 S(s) + 3 H2O +0.60
H2MoO4(aq) + 2 H+ + 2 e− ⇄ MoO2(s) + 2 H2O +0.65
1,4-Benzochinon.svg + 2 H+ + 2 e− ⇄ Hydrochinon2.svg +0.6992
O2(g) + 2 H+ + 2 e− ⇄ H2O2(aq) +0.70
Tl3+ + 3 e− ⇄ Tl(s) +0.72
PtCl62− + 2 e− ⇄ PtCl42− + 2 Cl− +0.726
H2SeO3(aq) + 4 H+ + 4 e− ⇄ Se(s) + 3 H2O +0.74
PtCl42− + 2 e− ⇄ Pt(s) + 4 Cl− +0.758
Fe3+ + e− ⇄ Fe2+ +0.77
Ag+ + e− ⇄ Ag(s) +0.7996
Hg22+ + 2 e− ⇄ 2 Hg(l) +0.80
NO3−(aq) + 2 H+ + e− ⇄ NO2(g) + H2O +0.80
[AuBr4]− + 3 e− ⇄ Au(s) + 4 Br− +0.85
Hg2+ + 2 e− ⇄ Hg(l) +0.85
MnO4− + H+ + e− ⇄ HMnO4− +0.90
2 Hg2+ + 2 e− ⇄ Hg22+ +0.91
Pd2+ + 2 e− ⇄ Pd(s) +0.915
[AuCl4]− + 3 e− ⇄ Au(s) + 4 Cl− +0.93
MnO2(s) + 4 H+ + e− ⇄ Mn3+ + 2 H2O +0.95
[AuBr2]− + e− ⇄ Au(s) + 2 Br− +0.96
Br2(l) + 2 e− ⇄ 2 Br− +1.066
Br2(aq) + 2 e− ⇄ 2 Br− +1.0873
IO3− + 5 H+ + 4 e− ⇄ HIO(aq) + 2 H2O +1.13
[AuCl2]− + e− ⇄ Au(s) + 2 Cl− +1.15
HSeO4− + 3 H+ + 2 e− ⇄ H2SeO3(aq) + H2O +1.15
Ag2O(s) + 2 H+ + 2 e− ⇄ 2 Ag(s) + H2O +1.17
ClO3− + 2 H+ + e− ⇄ ClO2(g) + H2O +1.18
Pt2+ + 2 e− ⇄ Pt(s) +1.188
ClO2(g) + H+ + e− ⇄ HClO2(aq) +1.19
2 IO3− + 12 H+ + 10 e− ⇄ I2(s) + 6 H2O +1.20
ClO4− + 2 H+ + 2 e− ⇄ ClO3− + H2O +1.20
O2(g) + 4 H+ + 4 e− ⇄ 2 H2O +1.23
MnO2(s) + 4 H+ + 2 e− ⇄ Mn2+ + 2H2O +1.23
Tl3+ + 2 e− ⇄ Tl+ +1.25
Cl2(g) + 2 e− ⇄ 2 Cl− +1.36
Cr2O72− + 14 H+ + 6 e− ⇄ 2 Cr3+ + 7 H2O +1.33
CoO2(s) + 4 H+ + e− ⇄ Co3+ + 2 H2O +1.42
2 NH3OH+ + H+ + 2 e− ⇄ N2H5+ + 2 H2O +1.42
2 HIO(aq) + 2 H+ + 2 e− ⇄ I2(s) + 2 H2O +1.44
Ce4+ + e− ⇄ Ce3+ +1.44
BrO3− + 5 H+ + 4 e− ⇄ HBrO(aq) + 2 H2O +1.45
β-PbO2(s) + 4 H+ + 2 e− ⇄ Pb2+ + 2 H2O +1.460
α-PbO2(s) + 4 H+ + 2 e− ⇄ Pb2+ + 2 H2O +1.468
2 BrO3− + 12 H+ + 10 e− ⇄ Br2(l) + 6 H2O +1.48
2ClO3− + 12 H+ + 10 e− ⇄ Cl2(g) + 6 H2O +1.49
MnO4− + 8 H+ + 5 e− ⇄ Mn2+ + 4 H2O +1.51
HO2• + H+ + e− ⇄ H2O2(aq) +1.51
Au3+ + 3 e− ⇄ Au(s) +1.52
NiO2(s) + 4 H+ + 2 e− ⇄ Ni2+ + 2 OH− +1.59
2 HClO(aq) + 2 H+ + 2 e− ⇄ Cl2(g) + 2 H2O +1.63
Ag2O3(s) + 6 H+ + 4 e− ⇄ 2 Ag+ + 3 H2O +1.67
HClO2(aq) + 2 H+ + 2 e− ⇄ HClO(aq) + H2O +1.67
Pb4+ + 2 e− ⇄ Pb2+ +1.69
MnO4− + 4 H+ + 3 e− ⇄ MnO2(s) + 2 H2O +1.70
H2O2(aq) + 2 H+ + 2 e− ⇄ 2 H2O +1.78
AgO(s) + 2 H+ + e− ⇄ Ag+ + H2O +1.77
Co3+ + e− ⇄ Co2+ +1.82
Au+ + e− ⇄ Au(s) +1.83
BrO4− + 2 H+ + 2 e− ⇄ BrO3− + H2O +1.85
Ag2+ + e− ⇄ Ag+ +1.98
S2O82− + 2 e− ⇄ 2 SO42− +2.010
O3(g) + 2 H+ + 2 e− ⇄ O2(g) + H2O +2.075
HMnO4− + 3 H+ + 2 e− ⇄ MnO2(s) + 2 H2O +2.09
F2(g) + 2 e− ⇄ 2 F− +2.87
F2(g) + 2 H+ + 2 e− ⇄ 2 HF(aq) +3.05

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