Standard Reduction Potentials by Element

Standard Reduction Potentials by Element

The following table provides Eo and Eo´ values 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.
Solids, gases, and liquids are identified; all other species are aqueous. Reduction reactions in acidic solution are written using H+ in place of H3O+. You may rewrite a reaction by replacing H+ with H3O+ and adding to the opposite side of the reaction one molecule of H2O per H+; thus

H3AsO4 + 2H+ + 2e– ⇌⇌ HAsO2 + 2H2O
becomes
H3AsO4 + 2H3O+ + 2e– ⇌⇌ HAsO2 + 4H2O
Conditions for formal potentials (Eo´) are listed next to the potential.
Aluminum E° (V)
Al3+ + 3e− ⇌⇌ Al(s) –1.676
Al(OH)4− + 3e− ⇌⇌ Al(s) + 4OH−
–2.310
AlF63− + 3e− ⇌⇌ Al(s) + 6F−
–2.07
Antimony
Sb + 3H+ + 3e− ⇌⇌ SbH3(g) –0.510
Sb2O5(s) + 6H+ + 4e− ⇌⇌ 2SbO+ + 3H2O(l)
0.605
SbO+ + 2H+ + 3e− ⇌⇌ Sb(s) + H2O(l)
0.212
Arsenic
As + 3H+ + 3e− ⇌⇌ AsH3(g) –0.225
H3AsO4 + 2H+ + 2e− ⇌⇌ HAsO2 + 2H2O(l)
0.560
HAsO2 + 3H+ + 3e− ⇌⇌ As(s) + 2H2O(l)
0.240
Barium
Ba2+ + 2e− ⇌⇌ Ba(s) –2.91
BaO(s) + 2H+ + 2e−⇌⇌ Ba(s) + H2O(l)
2.365
Beryllium
Be2+ + 2e− ⇌⇌ Be(s) –1.99
Bismuth
Bi3+ + 3e− ⇌⇌ Bi(s) 0.317
BiCl4− + 3e− ⇌⇌ Bi(s) + 4Cl−
0.199
Boron
B(OH)3 + 3H+ + 3e− ⇌⇌ B(s) + 3H2O(l) –0.890
B(OH)4− + 3e− ⇌⇌ B(s) + 4OH−
–1.811
Bromine
Br2 + 2e− ⇌⇌ 2Br− 1.087
HOBr + H+ + 2e− ⇌⇌ Br− + H2O(l)
1.341
HOBr + H+ + e− ⇌⇌ ½Br− + H2O(l)
1.604
BrO− + H2O(l) +2e− ⇌⇌ Br− + 2OH− 0.76 in 1 M NaOH
BrO3− + 6H+ + 5e− ⇌⇌ ½Br2(l) + 3H2O
1.5
BrO3− + 6H+ + 6e− ⇌⇌Br− + 3H2O
1.478
Cadmium
Cd2+ + 2e− ⇌⇌ Cd(s) –0.4030
Cd(CN)42− + 2e− ⇌⇌ Cd(s) + 4CN−
–0.943
Cd(NH3)42+ + 2e− ⇌⇌ Cd(s) + 4NH3
–0.622
Calcium
Ca2+ + 2e− ⇌⇌ Ca(s) –2.84
Carbon
CO2(g) + 2H+ + 2e− ⇌⇌ CO(g) + H2O(l) –0.106
CO2(g) + 2H+ + 2e− ⇌⇌ HCO2H
–0.20
2CO2(g) + 2H+ +2e− ⇌⇌ H2C2O4
–0.481
HCHO + 2H+ + 2e− ⇌⇌ CH3OH 0.2323
Cerium
Ce3+ + 3e− ⇌⇌ Ce(s) –2.336
Ce4+ + e− ⇌⇌ Ce3+ 1.44
Cesium
Cs+(aq)+e−⇌Cs(s)(P1.1)(P1.1)Cs+(aq)+e−⇌Cs(s)
-2.92
Chlorine
Cl2(g) + 2e−  ⇌⇌ 2Cl− 1.396
ClO− + H2O(l) + e− ⇌⇌½Cl2(g) + 2OH−
0.421 in 1 M NaOH
ClO− + H2O(l) + 2e− ⇌⇌ Cl− + 2OH−
0.890 in 1 M NaOH
HClO2 + 2H+ + 2e− ⇌⇌ HOCl + H2O
1.64
ClO3− + 2H+ + e− ⇌⇌ ClO2(g) + H2O
1.175
ClO3− + 3H+ + 2e−⇌⇌HClO2 + H2O
1.181
ClO4− + 2H+ + 2e−⇌⇌ ClO3− + H2O
1.201
ClO4-(aq) + H2O(l) + 2e- ⇌⇌ ClO3-(aq) + 2OH-(aq) 0.17
ClO3-(aq) + H2O(l) + 2e- ⇌⇌ ClO2-(aq) + 2OH-(aq) 0.35
ClO2-(aq) + H2O(l) + 2e- ⇌⇌ ClO-(aq) + 2OH-(aq) 0.59
Chromium
Cr3+ + e− ⇌⇌ Cr2+ –0.424
Cr2+ + 2e− ⇌⇌ Cr(s) –0.90
Cr2O72− + 14H+ + 6e−⇌⇌ 2Cr3+ + 7H2O(l)
1.36
CrO42− + 4H2O(l) + 3e−⇌⇌2Cr(OH)4− + 4OH−
–0.13 in 1 M NaOH
Cobalt
Co2+ + 2e− ⇌⇌ Co(s) –0.277
Co3+ + e− ⇌⇌ Co2+ 1.92
Co(NH3)63+ +e−  ⇌⇌ Co(NH3)62+
0.1
Co(OH)3(s) + e− ⇌⇌ Co(OH)2(s) + OH−
0.17
Co(OH)2(s) + 2e− ⇌⇌ Co(s) + 2OH−
–0.746
Copper
Cu+ + e− ⇌⇌ Cu(s) 0.520
Cu2+ + e− ⇌⇌ Cu+ 0.159
Cu2+ + 2e− ⇌⇌ Cu(s) 0.3419
Cu2+ + I− +e− ⇌⇌ CuI(s) 0.86
Cu2+ + Cl− + e− ⇌⇌ CuCl(s) 0.559
Fluorine
F2(g) + 2H+ + 2e− ⇌⇌ 2HF
3.053
F2(g) + 2e− ⇌⇌ 2F−
2.87
Gallium
Ga3++3e−⇌Ga(s)(P1.2)(P1.2)Ga3++3e−⇌Ga(s)
-0.56
Gold
Au+ + e− ⇌⇌ Au(s) 1.83
Au3+ + 2e− ⇌⇌ Au+
1.36
Au3+ + 3e− ⇌⇌ Au(s) 1.52
AuCl4− + 3e− ⇌⇌ Au(s) + 4Cl−
1.002
Hydrogen
2H++2e−⇌H2(g)(P1.3)(P1.3)2H++2e−⇌H2(g)
0.00000
H2O + e− ⇌⇌ ½H2(g) + OH−
–0.828
Iodine
I2(s)+2e−⇌2I−(P1.4)(P1.4)I2(s)+2e−⇌2I−
0.5355
I3− + 2e− ⇌⇌ 3I−
0.536
HIO + H+ + 2e− ⇌⇌ I− + H2O(l)
0.985
IO3− + 6H+ + 5e− ⇌⇌ ½I2(s) + 3H2O(l)
1.195
IO3−+ 3H2O(l) + 6e− ⇌⇌ I− + 6OH−
0.257
Iron
Fe2+ + 2e− ⇌⇌ Fe(s) –0.44
Fe3+ + 3e− ⇌⇌ Fe(s) –0.037
Fe3+ + e− ⇌⇌ Fe2+
0.771
Fe(CN)63− + e−⇌⇌ Fe(CN)64−
0.356
Fe(phen)63+ +e−⇌⇌Fe(phen)62+
1.147
Lanthanum
La3+ + 3e− ⇌⇌ La(s) –2.38
Lead
Pb2+ + 2e− ⇌⇌ Pb(s) –0.126
PbO2(s) + 4H+ +2e- ⇌⇌ Pb2+(aq) + 2H2O(l) 1.46
PbO2(s) + 4SO42− + 4H+ + 2e− ⇌⇌ PbSO4(s) + 2H2O(l)
1.690
PbSO4(s) + 2e− ⇌⇌ Pb(s) + SO42−
–0.356
Lithium
Li+ + e− ⇌⇌ Li(s) –3.040
Magnesium
Mg2+ + 2e− ⇌⇌ Mg(s) –2.356
Mg(OH)2(s) + 2e− ⇌⇌ Mg(s) + 2OH−
–2.687
Manganese
Mn2+ + 2e− ⇌⇌ Mn(s) –1.17
Mn3+ + e− ⇌⇌ Mn2+
1.5
MnO2(s) + 4H+ + 2e− ⇌⇌ Mn2+ + 2H2O(l)
1.23
MnO2(s) + 4H+ + e- ⇌⇌ Mn3+ (aq) + H2O(I) 0.95
MnO4− + 4H+ +3e− ⇌⇌ MnO2(s) + 2H2O(l)
1.70
MnO4−+ 8H+ + 5e− ⇌⇌ Mn2+ + 4H2O(l)
1.51
MnO4− + 2H2O(l) + 3e− ⇌⇌ MnO2(s) + 4OH− 0.60
Mercury
Hg2+ + 2e− ⇌⇌ Hg(l) 0.8535
2Hg2+ + 2e− ⇌⇌ Hg22+ 0.911
Hg22+ + 2e− ⇌⇌ 2Hg(l)
0.7960
Hg2Cl2(s) + 2e− ⇌⇌ 2Hg(l) + 2Cl−
0.2682
HgO(s) + 2H+ + 2e− ⇌⇌ Hg(l) + H2O(l)
0.926
Hg2Br2(s) + 2e− ⇌⇌ 2Hg(l) + 2Br−
1.392
Hg2I2(s) + 2e− ⇌⇌ 2Hg(l) + 2I−
–0.0405
Molybdenum
Mo3+ + 3e− ⇌⇌ Mo(s) –0.2
MoO2(s) + 4H+ + 4e− ⇌⇌ Mo(s) + 2H2O(l)
–0.152
MoO42− + 4H2O(l) + 6e− ⇌⇌Mo(s) + 8OH−
–0.913
Nickel
Ni2+ + 2e− ⇌⇌ Ni(s) –0.257
Ni(OH)2 + 2e− ⇌⇌ Ni(s) + 2OH−
–0.72
Ni(NH3)62+ + 2e− ⇌⇌ Ni(s) + 6NH3
–0.49
Nitrogen
N2(g)+5H++4e−⇌N2H+5(P1.5)(P1.5)N2(g)+5H++4e−⇌N2H5+
–0.23
N2O(g) + 2H+ + 2e− ⇌⇌ N2(g) + H2O(l)
1.77
2NO(g) + 2H+ + 2e− ⇌⇌ N2O(g) + H2O(l)
1.59
HNO2 + H+ +e− ⇌⇌ NO(g) + H2O(l)
0.996
2HNO2 + 4H+ + 4e− ⇌⇌ N2O(g) + 3H2O(l)
1.297
NO3− + 3H+ + 2e− ⇌⇌ HNO2 + H2O(l)
0.94
NO2(g)+H+(aq)+e−⇌HNO2(aq)(P1.6)(P1.6)NO2(g)+H+(aq)+e−⇌HNO2(aq)
1.07
NO3-(aq) + 4H+(aq) + 3e- ⇌⇌ NO(g) + 2H2O(l) 0.96
Oxygen
O2(g)+2H++2e−⇌H2O2(P1.7)(P1.7)O2(g)+2H++2e−⇌H2O2
0.695
O2(g) + 4H+ + 4e− ⇌⇌ 2H2O(l)
1.229
H2O2 + 2H+ + 2e− ⇌⇌ 2H2O(l)
1.763
O2(g) + 2H2O(l) + 4e− ⇌⇌ 4OH−
0.401
O3(g) + 2H+ + 2e− ⇌⇌ O2(g) + H2O(l)
2.07
O2 (g) + e- ⇌⇌ O2-(aq) -0.33
O2 (aq) + e- ⇌⇌ O2-(aq) -0.16
Phosphorous
P(s,white)+3H++3e−⇌PH3(g)(P1.8)(P1.8)P(s,white)+3H++3e−⇌PH3(g)
0.06
H3PO3+ 2H+ + 2e− ⇌⇌ H3PO2 + H2O(l)
-0.50
H3PO4 + 2H+ + 2e− ⇌⇌ H3PO3 + H2O(l)
-0.28
Platinum
Pt2+ + 2e− ⇌⇌ Pt(s) 1.2
PtCl42− + 2e− ⇌⇌ Pt(s) + 4Cl− 0.73
PtCl62− + 2e− ⇌⇌ PtCl42- + 2Cl− 0.68
Potassium
K+ + e− ⇌⇌ K(s) -2.93
Rubidium
Rb+ + e- ⇌⇌ Rb (s) -2.98
Ruthenium
Ru3+ + e− ⇌⇌ Ru2+ 0.249
RuO2(s) + 4H+ + 4e− ⇌⇌ Ru(s) + 2H2O(l)
0.68
Ru(NH3)63+ + e− ⇌⇌ Ru(s) + Ru(NH3)62+
0.10
Ru(CN)63− +e− ⇌⇌ Ru(s) + Ru(CN)64−
0.86
Selenium
Se(s)+2e−⇌Se2−(P1.9)(P1.9)Se(s)+2e−⇌Se2−
–0.67 in 1 M NaOH
Se(s) + 2H+ + 2e− ⇌⇌ H2Se(g)
–0.115
H2SeO3 + 4H+ + 4e− ⇌⇌ Se(s) + 3H2O(l)
0.74
SeO43− + 4H+ + e− ⇌⇌ H2SeO3 + H2O(l)
1.151
Silicon
SiF2−6+4e−⇌Si(s)+6F−(P1.10)(P1.10)SiF62−+4e−⇌Si(s)+6F−
–1.37
SiO2(s) + 4H+ + 4e− ⇌⇌ Si(s) + 2H2O(l)
–0.909
SiO2(s) + 8H+ + 8e− ⇌⇌ SiH4(g) + 2H2O(l)
–0.516
Silver
Ag+ + e− ⇌⇌ Ag(s) 0.7996
AgBr(s) + e− ⇌⇌ Ag(s) + Br− 0.071
 Ag2C2O4(s) + 2e− ⇌⇌ 2Ag(s) + C2O42−
0.47
AgCl(s) + e− ⇌⇌ Ag(s) + Cl− 0.2223
AgI(s) + e− ⇌⇌ Ag(s) + I− –0.152
Ag2S(s) + 2e− ⇌⇌ 2Ag(s) + S2−
–0.71
Ag(NH3)2+ + e− ⇌⇌ Ag(s) + 2NH3
–0.373
Sodium
Na++e−⇌Na(s)(P1.11)(P1.11)Na++e−⇌Na(s)
–2.713
Strontium
Sr2++2e−⇌Sr(s)(P1.12)(P1.12)Sr2++2e−⇌Sr(s)
–2.89
Sulfur
S(s)+2e−⇌S2−(P1.13)(P1.13)S(s)+2e−⇌S2−
–0.407
S(s) + 2H+ + 2e− ⇌⇌ H2S
0.144
S2O62− + 4H+ + 2e− ⇌⇌ 2H2SO3
0.569
S2O82− + 2e− ⇌⇌2SO42−
1.96
S4O62− + 2e− ⇌⇌2S2O32−
0.080
2SO32− + 2H2O(l) + 2e−⇌⇌ S2O42− + 4OH−
–1.13
2SO32− + 3H2O(l) + 4e−⇌⇌S2O32− + 6OH−
2SO42− + 4H+ + 2e−⇌⇌ S2O62− + 2H2O(l)
–0.25
SO42− + H2O(l) + 2e−⇌⇌ SO32−+ 2OH−
–0.936
SO42− + 4H+ + 2e−⇌⇌ H2SO32−+ H2O(l)
0.172
Thallium
Tl3++2e−⇌Tl+(P1.14)(P1.14)Tl3++2e−⇌Tl+
0.77 in 1 M HCl
Tl3+ + 3e− ⇌⇌ Tl(s) 0.742
Tin
Sn2+ + 2e−⇌⇌ Sn(s) -0.14
Sn4+ + 2e− ⇌⇌ Sn2+
0.154
Titanium
Ti2++2e−⇌Ti(s)(P1.15)(P1.15)Ti2++2e−⇌Ti(s)
–0.163
Ti3+ + e− ⇌⇌ Ti2+
–0.37
Tungsten
WO2(s)+4H++4e−⇌W(s)+2H2O(l)(P1.16)(P1.16)WO2(s)+4H++4e−⇌W(s)+2H2O(l)
–0.119
WO3(s) + 6H+ + 6e− ⇌⇌ W(s) + 3H2O(l)
–0.090
Uranium
U3+ + 3e− ⇌⇌ U(s) –1.66
U4+ + e− ⇌⇌ U3+
–0.52
UO2+ + 4H+ + e−⇌⇌U4+ + 2H2O(l)
0.27
UO22+ + e−⇌⇌UO2+
0.16
UO22+ + 4H+ + 2e−⇌⇌ U4+ + 2H2O(l)
0.327
Vanadium
V2++2e−⇌V(s)(P1.17)(P1.17)V2++2e−⇌V(s)
–1.13
V3+ + e− ⇌⇌ V2+
–0.255
VO2+ + 2H+ +e− ⇌⇌V3+ + H2O(l)
0.337
VO22+ + 2H+  +e− ⇌⇌ VO2+ + H2O(l)
1.000
Zinc
Zn2+(aq) + 2e− ⇌⇌ Zn(s)
–0.7618
Zn(OH)42− + 2e− ⇌⇌ Zn(s) + 4OH−
–1.285
Zn(NH3)42+ + 2e− ⇌⇌ Zn(s) + 4NH3
–1.04
Zn(CN)42− + 2e− ⇌⇌ Zn(s) + 4CN
–1.34

 

 

Standard electrode potential (data page)

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The data 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 (25.00 °C; 77.00 °F).
  • An effective concentration of 1 mol/L for each aqueous species or a species in a mercury amalgam (an alloy of mercury with another metal).
  • 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 (1 atm) rather than for the current standard of 100 kPa.
  • An activity of unity for each pure solid, pure liquid, or for water (solvent). The relation in electrode potential of metals in saltwater (as electrolyte) is given in the galvanic series.
  • Although many of the half cells are written for multiple-electron transfers, the tabulated potentials are for a single-electron transfer. All of the reactions should be divided by the stoichiometric coefficient for the electron to get the corresponding corrected reaction equation.
  • Divide the potentials by 0.059 V to get pe° values, which are necessary for the Nernst equation and other thermodynamic calculations.

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

Half-reaction  (V) Ref.
Oxidant Reductant
Sr+ + e Sr −4.101 [1]
Ca+ + e Ca −3.8 [1]
Pr3+ + e Pr2+ −3.1 [1]
3 N2(g) + 2H+ + 2e 2HN3(aq) −3.09 [2][3]
Li+ + e Li(s) −3.0401 [3][4]
N2(g) + 4H2O + 2e 2 NH2OH(aq) + 2OH −3.04 [2]
Cs+ + e Cs(s) −3.026 [3]
Ca(OH)2 + 2e Ca + 2 OH −3.02 [1]
Er3+ + e Er2+ −3.0 [1]
Ba(OH)2 + 2e Ba + 2 OH −2.99 [1]
Rb+ + e Rb(s) −2.98 [3]
K+ + e K(s) −2.931 [3]
Ba2+ + 2e Ba(s) −2.912 [3]
La(OH)3(s) + 3e La(s) + 3OH −2.90 [3]
Fr+ + e Fr −2.9 [1]
Sr2+ + 2e Sr(s) −2.899 [3]
Sr(OH)2 + 2e Sr + 2 OH −2.88 [1]
Ca2+ + 2e Ca(s) −2.868 [3][4]
Li+ + C6(s) + e LiC6(s) −2.84 [3]
Eu2+ + 2e Eu(s) −2.812 [3]
Ra2+ + 2e Ra(s) −2.8 [3]
Ho3+ + e Ho2+ −2.8 [1]
Bk3+ + e Bk2+ −2.8 [1]
Yb2+ + 2e Yb −2.76 [1]
Na+ + e Na(s) −2.71 [3][5]
Mg+ + e Mg −2.70 [1]
Nd3+ + e Nd2+ −2.7 [1]
Mg(OH)2 + 2e Mg + 2 OH −2.690 [1]
Sm2+ + 2e Sm −2.68 [1]
Be2O32− + 3 H2O + 4e 2 Be + 6 OH −2.63 [1]
Pm3+ + e Pm2+ −2.6 [1]
Dy3+ + e Dy2+ −2.6 [1]
No2+ + 2e No −2.50 [1]
HfO(OH)2 + H2O + 4e Hf + 4 OH −2.50 [1]
Th(OH)4 + 4e Th + 4 OH −2.48 [1]
Md2+ + 2e Md −2.40 [1]
Tm2+ + 2e Tm −2.4 [1]
La3+ + 3e La(s) −2.379 [3]
Y3+ + 3e Y(s) −2.372 [3]
Mg2+ + 2e Mg(s) −2.372 [3]
ZrO(OH)2(s) + H2O + 4e Zr(s) + 4OH −2.36 [3]
Pr3+ + 3e Pr −2.353 [1]
Ce3+ + 3e Ce −2.336 [1]
Er3+ + 3e Er −2.331 [1]
Ho3+ + 3e Ho −2.33 [1]
H2AlO3 + H2O + 3e Al + 4 OH −2.33 [1]
Nd3+ + 3e Nd −2.323 [1]
Tm3+ + 3e Tm −2.319 [1]
Al(OH)3(s) + 3e Al(s) + 3OH −2.31
Sm3+ + 3e Sm −2.304 [1]
Fm2+ + 2e Fm −2.30 [1]
Am3+ + e Am2+ −2.3 [1]
Dy3+ + 3e Dy −2.295 [1]
Lu3+ + 3e Lu −2.28 [1]
Tb3+ + 3e Tb −2.28 [1]
Gd3+ + 3e Gd −2.279 [1]
H2 + 2e 2 H −2.23 [1]
Es2+ + 2e Es −2.23 [1]
Pm2+ + 2e Pm −2.2 [1]
Tm3+ + e Tm2+ −2.2 [1]
Dy2+ + 2e Dy −2.2 [1]
Ac3+ + 3e Ac −2.20 [1]
Yb3+ + 3e Yb −2.19 [1]
Cf2+ + 2e Cf −2.12 [1]
Nd2+ + 2e Nd −2.1 [1]
Ho2+ + 2e Ho −2.1 [1]
Sc3+ + 3e Sc(s) −2.077 [6]
AlF63− + 3e Al + 6 F −2.069 [1]
Am3+ + 3e Am −2.048 [1]
Cm3+ + 3e Cm −2.04 [1]
Pu3+ + 3e Pu −2.031 [1]
Pr2+ + 2e Pr −2.0 [1]
Er2+ + 2e Er −2.0 [1]
Eu3+ + 3e Eu −1.991 [1]
Lr3+ + 3e Lr −1.96 [1]
Cf3+ + 3e Cf −1.94 [1]
Es3+ + 3e Es −1.91 [1]
Pa4+ + e Pa3+ −1.9 [1]
Am2+ + 2e Am −1.9 [1]
Th4+ + 4e Th −1.899 [1]
Fm3+ + 3e Fm −1.89 [1]
Np3+ + 3e Np −1.856 [1]
Be2+ + 2e Be −1.847 [1]
H2PO2 + e P + 2 OH −1.82 [1]
U3+ + 3e U −1.798 [1]
Sr2+ + 2e Sr(Hg) −1.793 [1]
H2BO3 + H2O + 3e B + 4 OH −1.79 [1]
ThO2 + 4H+ + 4e Th + 2 H2O −1.789 [1]
HfO2+ + 2 H+ + 4e Hf + H2O −1.724 [1]
HPO32− + 2 H2O + 3e P + 5 OH −1.71 [1]
SiO32− + H2O + 4e Si + 6 OH −1.697 [1]
Al3+ + 3e Al(s) −1.662 [1]
Ti2+ + 2e Ti(s) −1.63 [5]
ZrO2(s) + 4H+ + 4e Zr(s) + 2H2O −1.553 [7]
Zr4+ + 4e Zr(s) −1.45 [7]
Ti3+ + 3e Ti(s) −1.37 [8]
TiO(s) + 2H+ + 2e Ti(s) + H2O −1.31
Ti2O3(s) + 2H+ + 2e 2 TiO(s) + H2O −1.23
Zn(OH)42− + 2e Zn(s) + 4OH −1.199 [7]
Mn2+ + 2e Mn(s) −1.185 [7]
Fe(CN)64− + 6H+ + 2 e Fe(s) + 6HCN(aq) −1.16 [9]
Te(s) + 2e Te2− −1.143 [10]
V2+ + 2e V(s) −1.13 [10]
Nb3+ + 3e Nb(s) −1.099
Sn(s) + 4H+ + 4e SnH4(g) −1.07
SiO2(s) + 4H+ + 4e Si(s) + 2H2O −0.91
B(OH)3(aq) + 3H+ + 3e B(s) + 3H2O −0.89
Fe(OH)2(s) + 2e Fe(s) + 2OH −0.89 [9]
Fe2O3(s) + 3H2O + 2e 2Fe(OH)2(s) + 2OH −0.86 [9]
TiO2+ + 2H+ + 4e Ti(s) + H2O −0.86
2H2O + 2e H2(g) + 2OH −0.8277 [7]
Bi(s) + 3H+ + 3e BiH3 −0.8 [7]
Zn2+ + 2e Zn(Hg) −0.7628 [7]
Zn2+ + 2e Zn(s) −0.7618 [7]
Ta2O5(s) + 10H+ + 10e 2 Ta(s) + 5H2O −0.75
Cr3+ + 3e Cr(s) −0.74
Ag2S(s) + 2e 2Ag(s) + S2−(aq) −0.69
[Au(CN)2] + e Au(s) + 2 CN −0.60
Ta3+ + 3e Ta(s) −0.6
PbO(s) + H2O + 2e Pb(s) + 2OH −0.58
2 TiO2(s) + 2H+ + 2e Ti2O3(s) + H2O −0.56
Ga3+ + 3e Ga(s) −0.53
U4+ + e U3+ −0.52 [11]
H3PO2(aq) + H+ + e P(white)[note 1] + 2H2O −0.508 [7]
H3PO3(aq) + 2H+ + 2e H3PO2(aq) + H2O −0.499 [7]
H3PO3(aq) + 3H+ + 3e P(red)[note 1] + 3H2O −0.454 [7]
Fe2+ + 2e Fe(s) −0.44 [5]
2 CO2(g) + 2H+ + 2e HOOCCOOH(aq) −0.43
Cr3+ + e Cr2+ −0.42
Cd2+ + 2e Cd(s) −0.40 [5]
GeO2(s) + 2H+ + 2e GeO(s) + H2O −0.37
Cu2O(s) + H2O + 2e 2 Cu(s) + 2OH −0.360 [7]
PbSO4(s) + 2e Pb(s) + SO42− −0.3588 [7]
PbSO4(s) + 2e Pb(Hg) + SO42− −0.3505 [7]
Eu3+ + e Eu2+ −0.35 [11]
In3+ + 3e In(s) −0.34 [10]
Tl+ + e Tl(s) −0.34 [10]
Ge(s) + 4H+ + 4e GeH4(g) −0.29
Co2+ + 2e Co(s) −0.28 [7]
H3PO4(aq) + 2H+ + 2e H3PO3(aq) + H2O −0.276 [7]
V3+ + e V2+ −0.26 [5]
Ni2+ + 2e Ni(s) −0.25
As(s) + 3H+ + 3e AsH3(g) −0.23 [10]
AgI(s) + e Ag(s) + I −0.15224 [7]
MoO2(s) + 4H+ + 4e Mo(s) + 2H2O −0.15
Si(s) + 4H+ + 4e SiH4(g) −0.14
Sn2+ + 2e Sn(s) −0.13
O2(g) + H+ + e HO2•(aq) −0.13
Pb2+ + 2e Pb(s) −0.126 [5]
WO2(s) + 4H+ + 4e W(s) + 2H2O −0.12
P(red) + 3H+ + 3e PH3(g) −0.111 [7]
CO2(g) + 2H+ + 2e HCOOH(aq) −0.11
Se(s) + 2H+ + 2e H2Se(g) −0.11
CO2(g) + 2H+ + 2e CO(g) + H2O −0.11
SnO(s) + 2H+ + 2e Sn(s) + H2O −0.10
SnO2(s) + 4H+ + 4e SnO(s) + 2H2O −0.09
WO3(aq) + 6H+ + 6e W(s) + 3H2O −0.09 [10]
P(white) + 3H+ + 3e PH3(g) −0.063 [7]
Fe3+ + 3e Fe(s) −0.04 [9]
HCOOH(aq) + 2H+ + 2e HCHO(aq) + H2O −0.03
2H+ + 2e H2(g) 0.0000 = 0
AgBr(s) + e Ag(s) + Br +0.07133 [7]
S4O62− + 2e 2 S2O32− +0.08
Fe3O4(s) + 8H+ + 8e 3 Fe(s) + 4H2O +0.085 [12]
N2(g) + 2H2O + 6H+ + 6e 2 NH4OH(aq) +0.092
HgO(s) + H2O + 2e Hg(l) + 2OH +0.0977
Cu(NH3)42+ + e Cu(NH3)2+ + 2 NH3 +0.10 [10]
Ru(NH3)63+ + e Ru(NH3)62+ +0.10 [11]
N2H4(aq) + 4H2O + 2e 2 NH4+ + 4OH +0.11 [2]
H2MoO4(aq) + 6H+ + 6e Mo(s) + 4H2O +0.11
Ge4+ + 4e Ge(s) +0.12
C(s) + 4H+ + 4e CH4(g) +0.13 [10]
HCHO(aq) + 2H+ + 2e CH3OH(aq) +0.13
S(s) + 2H+ + 2e H2S(g) +0.14
Sn4+ + 2e Sn2+ +0.15
Cu2+ + e Cu+ +0.159 [10]
HSO4 + 3H+ + 2e SO2(aq) + 2H2O +0.16
UO22+ + e UO2+ +0.163 [11]
SO42− + 4H+ + 2e SO2(aq) + 2H2O +0.17
TiO2+ + 2H+ + e Ti3+ + H2O +0.19
SbO+ + 2H+ + 3e Sb(s) + H2O +0.20
AgCl(s) + e Ag(s) + Cl +0.22233 [7]
H3AsO3(aq) + 3H+ + 3e As(s) + 3H2O +0.24
GeO(s) + 2H+ + 2e Ge(s) + H2O +0.26
UO2+ + 4H+ + e U4+ + 2H2O +0.273 [11]
Re3+ + 3e Re(s) +0.300
Bi3+ + 3e Bi(s) +0.308 [7]
Cu2+ + 2e Cu(s) +0.337 [10]
VO2+ + 2H+ + e V3+ + H2O +0.34
[Fe(CN)6]3− + e [Fe(CN)6]4− +0.36
Fc+ + e Fc(s) +0.4 [13]
O2(g) + 2H2O + 4e 4OH(aq) +0.401 [5]
H2MoO4 + 6H+ + 3e Mo3+ + 2H2O +0.43
CH3OH(aq) + 2H+ + 2e CH4(g) + H2O +0.50
SO2(aq) + 4H+ + 4e S(s) + 2H2O +0.50
Cu+ + e Cu(s) +0.520 [10]
CO(g) + 2H+ + 2e C(s) + H2O +0.52
I3 + 2e 3 I +0.53 [5]
I2(s) + 2e 2 I +0.54 [5]
[AuI4] + 3e Au(s) + 4 I +0.56
H3AsO4(aq) + 2H+ + 2e H3AsO3(aq) + H2O +0.56
[AuI2] + e Au(s) + 2 I +0.58
S2O32 − + 6H+ + 4e 2 S(s) + 3H2O +0.60
H2MoO4(aq) + 2H+ + 2e MoO2(s) + 2H2O +0.65
3Fe2O3(s) + 2H+ + 2e Fe3O4(s) + H2O +0.66 [14]:p.100
1,4-Benzochinon.svg + 2H+ + 2e Hydrochinon2.svg +0.6992 [7]
O2(g) + 2H+ + 2e H2O2(aq) +0.70
Tl3+ + 3e Tl(s) +0.72
PtCl62− + 2e PtCl42− + 2 Cl +0.726 [11]
H2SeO3(aq) + 4H+ + 4e Se(s) + 3H2O +0.74
PtCl42− + 2e Pt(s) + 4 Cl +0.758 [11]
Fe3+ + e Fe2+ +0.77
Ag+ + e Ag(s) +0.7996 [7]
Hg22+ + 2e 2 Hg(l) +0.80
NO3(aq) + 2H+ + e NO2(g) + H2O +0.80
2FeO42− + 5H2O + 6e Fe2O3(s) + 10 OH +0.81 [9]
[AuBr4] + 3e Au(s) + 4 Br +0.85
Hg2+ + 2e Hg(l) +0.85
[IrCl6]2− + e [IrCl6]3− +0.87 [4]
MnO4 + H+ + e HMnO4 +0.90
2 Hg2+ + 2e Hg22+ +0.91 [10]
Pd2+ + 2e Pd(s) +0.915 [11]
[AuCl4] + 3e Au(s) + 4 Cl +0.93
Fe2O3(s) + 6H+ + 2e 2Fe2+ + 3H2O +0.94 [14]:p.100
MnO2(s) + 4H+ + e Mn3+ + 2H2O +0.95
NO3(aq) + 4H+ + 3e NO(g) + 2H2O(l) +0.958 [5]
[AuBr2] + e Au(s) + 2 Br +0.96
[HXeO6]3− + 2H2O + 2e [HXeO4] + 4 OH +0.99 [15]
[VO2]+(aq) + 2H+ + e [VO]2+(aq) + H2O +1.0 [16]
H6TeO6(aq) + 2H+ + 2e TeO2(s) + 4H2O +1.02 [16]
Br2(l) + 2e 2 Br +1.066 [7]
Br2(aq) + 2e 2 Br +1.0873 [7]
Fe3O4(s) + 8H+ + 2e 3Fe2+ + 4H2O +1.09 [14]:p.100
IO3 + 5H+ + 4e HIO(aq) + 2H2O +1.13
[AuCl2] + e Au(s) + 2 Cl +1.15
HSeO4 + 3H+ + 2e H2SeO3(aq) + H2O +1.15
Ag2O(s) + 2H+ + 2e 2 Ag(s) + H2O +1.17
ClO3 + 2H+ + e ClO2(g) + H2O +1.18
[HXeO6]3− + 5H2O + 8 e Xe(g) + 11OH +1.18 [15]
Pt2+ + 2e Pt(s) +1.188 [11]
ClO2(g) + H+ + e HClO2(aq) +1.19
2 IO3 + 12H+ + 10e I2(s) + 6H2O +1.20
ClO4 + 2H+ + 2e ClO3 + H2O +1.20
O2(g) + 4H+ + 4e 2H2O +1.229 [5]
MnO2(s) + 4H+ + 2e Mn2+ + 2H2O +1.23
[HXeO4] + 3H2O + 6 e Xe(g) + 7OH +1.24 [15]
Tl3+ + 2e Tl+ +1.25
Cr2O72− + 14H+ + 6e 2 Cr3+ + 7H2O +1.33
Cl2(g) + 2e 2 Cl +1.36 [5]
CoO2(s) + 4H+ + e Co3+ + 2H2O +1.42
2 NH3OH+ + H+ + 2e N2H5+ + 2H2O +1.42 [2]
2 HIO(aq) + 2H+ + 2e I2(s) + 2H2O +1.44
BrO3 + 5H+ + 4e HBrO(aq) + 2H2O +1.45
β-PbO2(s) + 4H+ + 2e Pb2+ + 2H2O +1.460 [10]
α-PbO2(s) + 4H+ + 2e Pb2+ + 2H2O +1.468 [10]
2 BrO3 + 12H+ + 10e Br2(l) + 6H2O +1.48
2ClO3 + 12H+ + 10e Cl2(g) + 6H2O +1.49
HClO(aq) + H+ + 2e Cl(aq) + H2O +1.49 [1]
MnO4 + 8H+ + 5e Mn2+ + 4H2O +1.51
HO2 + H+ + e H2O2(aq) +1.51
Au3+ + 3e Au(s) +1.52
NiO2(s) + 2H+ + 2e Ni2+ + 2OH +1.59
Ce4+ + e Ce3+ +1.61
2 HClO(aq) + 2H+ + 2e Cl2(g) + 2H2O +1.63
Ag2O3(s) + 6H+ + 4e 2 Ag+ + 3H2O +1.67
HClO2(aq) + 2H+ + 2e HClO(aq) + H2O +1.67
Pb4+ + 2e Pb2+ +1.69 [10]
MnO4 + 2H2O + 3e MnO2(s) + 4OH +1.692
MnO4 + 4H+ + 3e MnO2(s) + 2H2O +1.70
AgO(s) + 2H+ + e Ag+ + H2O +1.77
H2O2(aq) + 2H+ + 2e 2H2O +1.78
Co3+ + e Co2+ +1.82
Au+ + e Au(s) +1.83 [10]
BrO4 + 2H+ + 2e BrO3 + H2O +1.85
Ag2+ + e Ag+ +1.98 [10]
S2O82− + 2e 2 SO42− +2.010 [7]
O3(g) + 2H+ + 2e O2(g) + H2O +2.075 [11]
HMnO4 + 3H+ + 2e MnO2(s) + 2H2O +2.09
XeO3(aq) + 6H+ + 6 e Xe(g) + 3H2O +2.12 [15]
H4XeO6(aq) + 8H+ + 8 e Xe(g) + 6 H2O +2.18 [15]
FeO42− + 3e + 8H+ Fe3+ + 4H2O +2.20 [17]
XeF2(aq) + 2H+ + 2e Xe(g) + 2HF(aq) +2.32 [15]
H4XeO6(aq) + 2H+ + 2e XeO3(aq) + 3H2O +2.42 [15]
F2(g) + 2e 2 F +2.87 [4][5][10]
F2(g) + 2H+ + 2e 2 HF(aq) +3.05 [10]
KrF2(aq) + 2e  Kr(g) + 2 F(aq) +3.27 [18]
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