Standard Electrode Potential (data Page)

The values of standard electrode potentials are given in the table below in volts relative to the standard hydrogen electrode and are for the following conditions:

  • A temperature of 298.15 K (25 °C);
  • An effective concentration of 1 mol/L for each aqueous species or a species in a mercury amalgam;
  • A 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.
  • An activity of unity for each pure solid, pure liquid, or for water (solvent).

Legend: (s) – solid; (l) – liquid; (g) – gas; (aq) – aqueous (default for all charged species); (Hg) – amalgam.

Half-reaction E° (V) Ref.
& -9
Zz 9
Sr+ +  e− Sr -3.80 −3.80
Ca+ +  e− Ca -3.80 −3.80
Pr3+ +  e− Pr2+ -3.1 −3.1
N3⁄2 N2(g) +  H+ +  e− HN3(aq) -3.09 −3.09
Li+ +  e− Li(s) -3.0401 −3.0401
N2(g) + 4 H2O + 2 e− 2 NH2OH(aq) + 2 OH− -3.04 −3.04
Cs+ +  e− Cs(s) -3.026 −3.026
Ca(OH)2 + 2 e− Ca + 2 OH- -3.02 −3.02
Er3+ +  e− Er2+ -3.0 −3.0
Ba(OH)2 + 2 e− Ba + 2 OH- -2.99 −2.99
Rb+ +  e− Rb(s) -2.98 −2.98
K+ +  e− K(s) -2.931 −2.931
Ba2+ + 2 e− Ba(s) -2.912 −2.912
La(OH)3(s) + 3 e− La(s) + 3 OH− -2.90 −2.90
Fr+ +  e− Fr -2.9 −2.9
Sr2+ + 2 e− Sr(s) -2.899 −2.899
Sr(OH)2 + 2 e− Sr + 2 OH- -2.88 −2.88
Ca2+ + 2 e− Ca(s) -2.868 −2.868
Eu2+ + 2 e− Eu(s) -2.812 −2.812
Ra2+ + 2 e− Ra(s) -2.8 −2.8
Ho3+ +  e− Ho2+ -2.8 −2.8
Bk3+ +  e− Bk2+ -2.8 −2.8
Yb2+ + 2 e− Yb -2.76 −2.76
Na+ +  e− Na(s) -2.71 −2.71
Mg+ +  e− Mg -2.70 −2.70
Nd3+ +  e− Nd2+ -2.7 −2.7
Mg(OH)2 + 2 e− Mg + 2 OH- -2.690 −2.690
Sm2+ + 2 e− Sm -2.68 −2.68
Be2O32- + 3 H2O + 4 e− 2 Be + 6 OH- -2.63 −2.63
Pm3+ +  e− Pm2+ -2.6 −2.6
Dy3+ +  e− Dy2+ -2.6 −2.6
No2+ + 2 e− No -2.50 −2.50
HfO(OH)2 + H2O + 4 e− Hf + 4 OH- -2.50 −2.50
Th(OH)4 + 4 e− Th + 4 OH- -2.48 −2.48
Md2+ + 2 e− Md -2.40 −2.40
Tm2+ + 2 e− Tm -2.4 −2.4
La3+ + 3 e− La(s) -2.379 −2.379
Y3+ + 3 e− Y(s) -2.372 −2.372
Mg2+ + 2 e− Mg(s) -2.372 −2.372
ZrO(OH)2(s) +  H2O + 4 e− Zr(s) + 4 OH− -2.36 −2.36
Pr3+ + 3 e− Pr -2.353 −2.353
Ce3+ + 3 e− Ce -2.336 −2.336
Er3+ + 3 e− Er -2.331 −2.331
Ho3+ + 3 e− Ho -2.33 −2.33
H2AlO3- + H2O + 3 e− Al + 4 OH- -2.33 −2.33
Nd3+ + 3 e− Nd -2.323 −2.323
Tm3+ + 3 e− Tm -2.319 −2.319
Al(OH)3(s) + 3 e− Al(s) + 3 OH− -2.31 −2.31
Sm3+ + 3 e− Sm -2.304 −2.304
Pr3+ + 3 e− Pr -2.30 −2.30
Fm2+ + 2 e− Fm -2.30 −2.30
Am3+ +  e− Am2+ -2.3 −2.3
Dy3+ + 3 e− Dy -2.295 −2.295
Lu3+ + 3 e− Lu -2.28 −2.28
Tb3+ + 3 e− Tb -2.28 −2.28
Gd3+ + 3 e− Gd -2.279 −2.279
H2 + 2 e− 2 H- -2.23 −2.23
Es2+ + 2 e− Es -2.23 −2.23
Pm2+ + 2 e− Pm -2.2 −2.2
Tm3+ +  e− Tm2+ -2.2 −2.2
Dy2+ + 2 e− Dy -2.2 −2.2
Ac3+ + 3 e− Ac -2.20 −2.20
Yb3+ + 3 e− Yb -2.19 −2.19
Cf2+ + 2 e− Cf -2.12 −2.12
Nd2+ + 2 e− Nd -2.1 −2.1
Ho2+ + 2 e− Ho -2.1 −2.1
Sc3+ + 3 e− Sc(s) -2.077 −2.077
AlF63- + 3 e− Al + 6 F- -2.069 −2.069
Am3+ + 3 e− Am -2.048 −2.048
Cm3+ + 3 e− Cm -2.04 −2.04
Pu3+ + 3 e− Pu -2.031 −2.031
Pr2+ + 2 e− Pr -2.0 −2.0
Er2+ + 2 e− Er -2.0 −2.0
Eu3+ + 3 e− Eu -1.991 −1.991
Lr3+ + 3 e− Lr -1.96 −1.96
Cf3+ + 3 e− Cf -1.94 −1.94
Es3+ + 3 e− Es -1.91 −1.91
Pa4+ +  e− Pa3+ -1.9 −1.9
Am2+ + 2 e− Am -1.9 −1.9
Th4+ + 4 e− Th -1.899 −1.899
Fm3+ + 3 e− Fm -1.89 −1.89
Np3+ + 3 e− Np -1.856 −1.856
Be2+ + 2 e− Be -1.847 −1.847
H2PO2- +  e− P + 2 OH- -1.82 −1.82
U3+ + 3 e− U -1.798 −1.798
Sr2+ + 2 e− Sr/Hg -1.793 −1.793
H2BO3- + H2O + 3 e− B + 4 OH- -1.79 −1.79
ThO2 + 4H+ + 4 e− Th + 2 H2O -1.789 −1.789
HfO2+ + 2 H+ + 4 e− Hf + H2O -1.724 −1.724
HPO32- + 2 H2O + 3 e− P + 5 OH- -1.71 −1.71
SiO32- + H2O + 4 e− Si + 6 OH- -1.697 −1.697
Al3+ + 3 e− Al(s) -1.662 −1.662
Ti2+ + 2 e− Ti(s) -1.63 −1.63
ZrO2(s) + 4 H+ + 4 e− Zr(s) + 2 H2O -1.553 −1.553
Zr4+ + 4 e− Zr(s) -1.45 −1.45
Ti3+ + 3 e− Ti(s) -1.37 −1.37
TiO(s) + 2 H+ + 2 e− Ti(s) +  H2O -1.31 −1.31
Ti2O3(s) + 2 H+ + 2 e− 2 TiO(s) +  H2O -1.23 −1.23
Zn(OH)42− + 2 e− Zn(s) + 4 OH− -1.199 −1.199
Mn2+ + 2 e− Mn(s) -1.185 −1.185
Fe(CN)64− + 6 H+ + 2  e− Fe(s) + 6HCN(aq) -1.16 −1.16
Te(s) + 2 e− Te2− -1.143 −1.143
V2+ + 2 e− V(s) -1.13 −1.13
Nb3+ + 3 e− Nb(s) -1.099 −1.099
Sn(s) + 4 H+ + 4 e− SnH4(g) -1.07 −1.07
SiO2(s) + 4 H+ + 4 e− Si(s) + 2 H2O -0.91 −0.91
B(OH)3(aq) + 3 H+ + 3 e− B(s) + 3 H2O -0.89 −0.89
Fe(OH)2(s) + 2 e− Fe(s) + 2 OH− -0.89 −0.89
Fe2O3(s) + 3 H2O + 2 e− 2Fe(OH)2(s) + 2 OH− -0.86 −0.86
TiO2+ + 2 H+ + 4 e− Ti(s) +  H2O -0.86 −0.86
H2 H2O + 2 e− H2(g) + 2 OH− -0.8277 −0.8277
Bi(s) + 3 H+ + 3 e− BiH3 -0.8 −0.8
Zn2+ + 2 e− Zn(Hg) -0.7628 −0.7628
Zn2+ + 2 e− Zn(s) -0.7618 −0.7618
Ta2O5(s) + 10 H+ + 10 e− 2 Ta(s) + 5 H2O -0.75 −0.75
Cr3+ + 3 e− Cr(s) -0.74 −0.74
Au− +  e− Au(s) + 2 CN− -0.60 −0.60
Ta3+ + 3 e− Ta(s) -0.6 −0.6
PbO(s) +  H2O + 2 e− Pb(s) + 2 OH− -0.58 −0.58
Ti2 TiO2(s) + 2 H+ + 2 e− Ti2O3(s) +  H2O -0.56 −0.56
Ga3+ + 3 e− Ga(s) -0.53 −0.53
U4+ +  e− U3+ -0.52 −0.52
P H3PO2(aq) +  H+ +  e− P(white) + 2 H2O -0.508 −0.508
P H3PO3(aq) + 2 H+ + 2 e− H3PO2(aq) +  H2O -0.499 −0.499
P H3PO3(aq) + 3 H+ + 3 e− P(red) + 3 H2O -0.454 −0.454
Fe2+ + 2 e− Fe(s) -0.44 −0.44
C2 CO2(g) + 2 H+ + 2 e− HOOCCOOH(aq) -0.43 −0.43
Cr3+ +  e− Cr2+ -0.42 −0.42
Cd2+ + 2 e− Cd(s) -0.40 −0.40
GeO2(s) + 2 H+ + 2 e− GeO(s) +  H2O -0.37 −0.37
Cu2O(s) +  H2O + 2 e− 2 Cu(s) + 2 OH− -0.360 −0.360
PbSO4(s) + 2 e− Pb(s) + SO42− -0.3588 −0.3588
PbSO4(s) + 2 e− Pb(Hg) + SO42− -0.3505 −0.3505
Eu3+ +  e− Eu2+ -0.35 −0.35
In3+ + 3 e− In(s) -0.34 −0.34
Tl+ +  e− Tl(s) -0.34 −0.34
Ge(s) + 4 H+ + 4 e− GeH4(g) -0.29 −0.29
Co2+ + 2 e− Co(s) -0.28 −0.28
P H3PO4(aq) + 2 H+ + 2 e− H3PO3(aq) +  H2O -0.276 −0.276
V3+ +  e− V2+ -0.26 −0.26
Ni2+ + 2 e− Ni(s) -0.25 −0.25
As(s) + 3 H+ + 3 e− AsH3(g) -0.23 −0.23
AgI(s) +  e− Ag(s) + I− -0.15224 −0.15224
MoO2(s) + 4 H+ + 4 e− Mo(s) + 2 H2O -0.15 −0.15
Si(s) + 4 H+ + 4 e− SiH4(g) -0.14 −0.14
Sn2+ + 2 e− Sn(s) -0.13 −0.13
O2(g) +  H+ +  e− HO2•(aq) -0.13 −0.13
Pb2+ + 2 e− Pb(s) -0.13 −0.13
WO2(s) + 4 H+ + 4 e− W(s) + 2 H2O -0.12 −0.12
P(red) + 3 H+ + 3 e− PH3(g) -0.111 −0.111
C CO2(g) + 2 H+ + 2 e− HCOOH(aq) -0.11 −0.11
Se(s) + 2 H+ + 2 e− H2Se(g) -0.11 −0.11
C CO2(g) + 2 H+ + 2 e− CO(g) +  H2O -0.11 −0.11
SnO(s) + 2 H+ + 2 e− Sn(s) +  H2O -0.10 −0.10
SnO2(s) + 2 H+ + 2 e− SnO(s) +  H2O -0.09 −0.09
WO3(aq) + 6 H+ + 6 e− W(s) + 3 H2O -0.09 −0.09
P(white) + 3 H+ + 3 e− PH3(g) -0.063 −0.063
Fe3+ + 3 e− Fe(s) -0.04 −0.04
C HCOOH(aq) + 2 H+ + 2 e− HCHO(aq) +  H2O -0.03 −0.03
H 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 + 6 H+ + 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
Mo 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
C 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
S HSO4− + 3 H+ + 2 e− SO2(aq) + 2 H2O +0.16
UO22+ +  e− UO2+ +0.163
S 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
As 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 3− +  e− 4− +0.36
O2(g) + 2 H2O + 4 e− 4 OH−(aq) +0.40
Mo H2MoO4 + 6 H+ + 3 e− Mo3+ + 2 H2O +0.43
C CH3OH(aq) + 2 H+ + 2 e− CH4(g) +  H2O +0.50
S SO2(aq) + 4 H+ + 4 e− S(s) + 2 H2O +0.50
Cu+ +  e− Cu(s) +0.520
C CO(g) + 2 H+ + 2 e− C(s) +  H2O +0.52
I3− + 2 e− 3 I− +0.53
I2(s) + 2 e− 2 I− +0.54
Au − + 3 e− Au(s) + 4 I− +0.56
As H3AsO4(aq) + 2 H+ + 2 e− H3AsO3(aq) +  H2O +0.56
Au − +  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
Fc+ +  e− Fc(s) +0.641
Mo H2MoO4(aq) + 2 H+ + 2 e− MoO2(s) + 2 H2O +0.65
C + 2 H+ + 2 e− +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
Se 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
N NO3−(aq) + 2 H+ +  e− NO2(g) +  H2O +0.80
Fe 2FeO42− + 5 H2O + 6 e− Fe2O3(s) + 10  OH− +0.81
Au − + 3 e− Au(s) + 4 Br− +0.85
Hg2+ + 2 e− Hg(l) +0.85
Ir 2- +  e− 3- +0.87
MnO4− +  H+ +  e− HMnO4− +0.90
Hg2 Hg2+ + 2 e− Hg22+ +0.91
Pd2+ + 2 e− Pd(s) +0.915
Au − + 3 e− Au(s) + 4 Cl− +0.93
MnO2(s) + 4 H+ +  e− Mn3+ + 2 H2O +0.95
Au− +  e− Au(s) + 2 Br− +0.96
Xe3− + 2 H2O + 2 e− + − + 4  OH− +0.99
TeH6TeO6(aq) + 2 H+ + 2 e− TeO2(s) + 4 H2O +1.02
Br2(l) + 2 e− 2 Br− +1.066
Br2(aq) + 2 e− 2 Br− +1.0873
I IO3− + 5 H+ + 4 e− HIO(aq) + 2 H2O +1.13
Au − +  e− Au(s) + 2 Cl− +1.15
Se 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
Xe3− + 5 H2O + 8  e− Xe(g) + 11 OH− +1.18
Pt2+ + 2 e− Pt(s) +1.188
ClO2(g) +  H+ +  e− HClO2(aq) +1.19
I 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 +1.229
MnO2(s) + 4 H+ + 2 e− Mn2+ + 2 H2O +1.23
Xe− + 3 H2O + 6  e− Xe(g) + 7 OH− +1.24
Tl3+ + 2 e− Tl+ +1.25
Cr2O72− + 14 H+ + 6 e− 2 Cr3+ + 7 H2O +1.33
Cl2(g) + 2 e− 2 Cl− +1.36
CoO2(s) + 4 H+ +  e− Co3+ + 2 H2O +1.42
N 2 NH3O H+ +  H+ + 2 e− N2H5+ + 2 H2O +1.42
I 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
PbO β-PbO2(s) + 4 H+ + 2 e− Pb2+ + 2 H2O +1.460
PbO α-PbO2(s) + 4 H+ + 2 e− Pb2+ + 2 H2O +1.468
Br 2 BrO3− + 12 H+ + 10 e− Br2(l) + 6 H2O +1.48
Cl 2ClO3− + 12 H+ + 10 e− Cl2(g) + 6 H2O +1.49
MnO4− + 8 H+ + 5 e− Mn2+ + 4 H2O +1.51
O 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
Cl 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
Cl 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
AgO(s) + 2 H+ +  e− Ag+ +  H2O +1.77
O  H2O2(aq) + 2 H+ + 2 e− 2 H2O +1.78
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
Mn HMnO4− + 3 H+ + 2 e− MnO2(s) + 2 H2O +2.09
XeO3(aq) + 6 H+ + 6  e− Xe(g) + 3 H2O +2.12
XeH4XeO6(aq) + 8 H+ + 8  e− Xe(g) + 6  H2O +2.18
FeO42− + 3 e− + 8 H+ Fe3+ + 4 H2O +2.20
XeF2(aq) + 2 H+ + 2 e− Xe(g) + 2HF(aq) +2.32
XeH4XeO6(aq) + 2 H+ + 2 e− XeO3(aq) +  H2O +2.42
F2(g) + 2 e− 2 F− +2.87
F2(g) + 2 H+ + 2 e− 2 HF(aq) +3.05

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