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).
- 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 (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 | E° (V) | ||
|---|---|---|---|
| Oxidant | ⇌ | Reductant | |
| Sr+ + e− | ⇌ | Sr | −4.101 |
| Ca+ + e− | ⇌ | Ca | −3.8 |
| Pr3+ + e− | ⇌ | Pr2+ | −3.1 |
| 3 N2(g) + 2 H+ + 2 e− | ⇌ | 2HN3(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 |
| Ca(OH)2 + 2 e− | ⇌ | Ca + 2 OH− | −3.02 |
| Er3+ + e− | ⇌ | Er2+ | −3.0 |
| Ba(OH)2 + 2 e− | ⇌ | Ba + 2 OH− | −2.99 |
| 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) + 3 OH− | −2.90 |
| Fr+ + e− | ⇌ | Fr | −2.9 |
| Sr2+ + 2 e− | ⇌ | Sr(s) | −2.899 |
| Sr(OH)2 + 2 e− | ⇌ | Sr + 2 OH− | −2.88 |
| Ca2+ + 2 e− | ⇌ | Ca(s) | −2.868 |
| Li+ + C6(s) + e− | ⇌ | LiC6(s) | −2.84 |
| Eu2+ + 2 e− | ⇌ | Eu(s) | −2.812 |
| Ra2+ + 2 e− | ⇌ | Ra(s) | −2.8 |
| Ho3+ + e− | ⇌ | Ho2+ | −2.8 |
| Bk3+ + e− | ⇌ | Bk2+ | −2.8 |
| Yb2+ + 2 e− | ⇌ | Yb | −2.76 |
| Na+ + e− | ⇌ | Na(s) | −2.71 |
| Mg+ + e− | ⇌ | Mg | −2.70 |
| Nd3+ + e− | ⇌ | Nd2+ | −2.7 |
| Mg(OH)2 + 2 e− | ⇌ | Mg + 2 OH− | −2.690 |
| Sm2+ + 2 e− | ⇌ | Sm | −2.68 |
| Be2O32− + 3 H2O + 4 e− | ⇌ | 2 Be + 6 OH− | −2.63 |
| Pm3+ + e− | ⇌ | Pm2+ | −2.6 |
| Dy3+ + e− | ⇌ | Dy2+ | −2.6 |
| No2+ + 2 e− | ⇌ | No | −2.50 |
| HfO(OH)2 + H2O + 4 e− | ⇌ | Hf + 4 OH− | −2.50 |
| Th(OH)4 + 4 e− | ⇌ | Th + 4 OH− | −2.48 |
| Md2+ + 2 e− | ⇌ | Md | −2.40 |
| Tm2+ + 2 e− | ⇌ | Tm | −2.4 |
| 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) + 4 OH− | −2.36 |
| Pr3+ + 3 e− | ⇌ | Pr | −2.353 |
| Ce3+ + 3 e− | ⇌ | Ce | −2.336 |
| Er3+ + 3 e− | ⇌ | Er | −2.331 |
| Ho3+ + 3 e− | ⇌ | Ho | −2.33 |
| H2AlO3− + H2O + 3 e− | ⇌ | Al + 4 OH− | −2.33 |
| Nd3+ + 3 e− | ⇌ | Nd | −2.323 |
| Tm3+ + 3 e− | ⇌ | Tm | −2.319 |
| Al(OH)3(s) + 3 e− | ⇌ | Al(s) + 3 OH− | −2.31 |
| Sm3+ + 3 e− | ⇌ | Sm | −2.304 |
| Fm2+ + 2 e− | ⇌ | Fm | −2.30 |
| Am3+ + e− | ⇌ | Am2+ | −2.3 |
| Dy3+ + 3 e− | ⇌ | Dy | −2.295 |
| Lu3+ + 3 e− | ⇌ | Lu | −2.28 |
| Tb3+ + 3 e− | ⇌ | Tb | −2.28 |
| Gd3+ + 3 e− | ⇌ | Gd | −2.279 |
| H2 + 2 e− | ⇌ | 2 H− | −2.23 |
| Es2+ + 2 e− | ⇌ | Es | −2.23 |
| Pm2+ + 2 e− | ⇌ | Pm | −2.2 |
| Tm3+ + e− | ⇌ | Tm2+ | −2.2 |
| Dy2+ + 2 e− | ⇌ | Dy | −2.2 |
| Ac3+ + 3 e− | ⇌ | Ac | −2.20 |
| Yb3+ + 3 e− | ⇌ | Yb | −2.19 |
| Cf2+ + 2 e− | ⇌ | Cf | −2.12 |
| Nd2+ + 2 e− | ⇌ | Nd | −2.1 |
| Ho2+ + 2 e− | ⇌ | Ho | −2.1 |
| Sc3+ + 3 e− | ⇌ | Sc(s) | −2.077 |
| AlF63− + 3 e− | ⇌ | Al + 6 F− | −2.069 |
| Am3+ + 3 e− | ⇌ | Am | −2.048 |
| Cm3+ + 3 e− | ⇌ | Cm | −2.04 |
| Pu3+ + 3 e− | ⇌ | Pu | −2.031 |
| Pr2+ + 2 e− | ⇌ | Pr | −2.0 |
| Er2+ + 2 e− | ⇌ | Er | −2.0 |
| Eu3+ + 3 e− | ⇌ | Eu | −1.991 |
| Lr3+ + 3 e− | ⇌ | Lr | −1.96 |
| Cf3+ + 3 e− | ⇌ | Cf | −1.94 |
| Es3+ + 3 e− | ⇌ | Es | −1.91 |
| Pa4+ + e− | ⇌ | Pa3+ | −1.9 |
| Am2+ + 2 e− | ⇌ | Am | −1.9 |
| Th4+ + 4 e− | ⇌ | Th | −1.899 |
| Fm3+ + 3 e− | ⇌ | Fm | −1.89 |
| Np3+ + 3 e− | ⇌ | Np | −1.856 |
| Be2+ + 2 e− | ⇌ | Be | −1.847 |
| H2PO2− + e− | ⇌ | P + 2 OH− | −1.82 |
| U3+ + 3 e− | ⇌ | U | −1.798 |
| Sr2+ + 2 e− | ⇌ | Sr(Hg) | −1.793 |
| H2BO3− + H2O + 3 e− | ⇌ | B + 4 OH− | −1.79 |
| ThO2 + 4H+ + 4 e− | ⇌ | Th + 2 H2O | −1.789 |
| HfO2+ + 2 H+ + 4 e− | ⇌ | Hf + H2O | −1.724 |
| HPO32− + 2 H2O + 3 e− | ⇌ | P + 5 OH− | −1.71 |
| SiO32− + H2O + 4 e− | ⇌ | Si + 6 OH− | −1.697 |
| Al3+ + 3 e− | ⇌ | Al(s) | −1.662 |
| 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 |
| Ti3+ + 3 e− | ⇌ | Ti(s) | −1.37 |
| TiO(s) + 2 H+ + 2 e− | ⇌ | Ti(s) + H2O | −1.31 |
| Ti2O3(s) + 2 H+ + 2 e− | ⇌ | 2 TiO(s) + H2O | −1.23 |
| Zn(OH)42− + 2 e− | ⇌ | Zn(s) + 4 OH− | −1.199 |
| Mn2+ + 2 e− | ⇌ | Mn(s) | −1.185 |
| Fe(CN)64− + 6 H+ + 2 e− | ⇌ | Fe(s) + 6HCN(aq) | −1.16 |
| 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 |
| Fe(OH)2(s) + 2 e− | ⇌ | Fe(s) + 2 OH− | −0.89 |
| Fe2O3(s) + 3 H2O + 2 e− | ⇌ | 2Fe(OH)2(s) + 2 OH− | −0.86 |
| TiO2+ + 2 H+ + 4 e− | ⇌ | Ti(s) + H2O | −0.86 |
| 2H2O + 2 e− | ⇌ | H2(g) + 2 OH− | −0.8277 |
| Bi(s) + 3 H+ + 3 e− | ⇌ | BiH3 | −0.8 |
| 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 |
| Ag2S(s) + 2 e− | ⇌ | 2Ag(s) + S2−(aq) | −0.69 |
| [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 |
| 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] + 3 H2O | −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 |
| AgI(s) + e− | ⇌ | Ag(s) + I− | −0.15224 |
| 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) | −0.126 |
| 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) + 4 H+ + 4 e− | ⇌ | SnO(s) + 2 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 |
| Fe3+ + 3 e− | ⇌ | Fe(s) | −0.04 |
| HCOOH(aq) + 2 H+ + 2 e− | ⇌ | HCHO(aq) + H2O | −0.03 |
| 2 H+ + 2 e− | ⇌ | H2(g) | 0.0000 |
| 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 |
| 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 |
| Cu2+ + 2 e− | ⇌ | Cu(s) | +0.337 |
| VO2+ + 2 H+ + e− | ⇌ | V3+ + H2O | +0.34 |
| [Fe(CN)6]3− + e− | ⇌ | [Fe(CN)6]4− | +0.36 |
| Fc+ + e− | ⇌ | Fc(s) | +0.4 |
| O2(g) + 2 H2O + 4 e− | ⇌ | 4 OH−(aq) | +0.401 |
| 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 |
| I3− + 2 e− | ⇌ | 3 I− | +0.53 |
| I2(s) + 2 e− | ⇌ | 2 I− | +0.54 |
| [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 |
| S2O32 − + 6 H+ + 4 e− | ⇌ | 2 S(s) + 3 H2O | +0.60 |
| H2MoO4(aq) + 2 H+ + 2 e− | ⇌ | MoO2(s) + 2 H2O | +0.65 |
| 3Fe2O3(s) + 2 H+ + 2 e− | ⇌ | 2 Fe3O4(s) + H2O | +0.66 |
 + 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 |
| 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 |
| 2FeO42− + 5 H2O + 6 e− | ⇌ | Fe2O3(s) + 10 OH− | +0.81 |
| [AuBr4]− + 3 e− | ⇌ | Au(s) + 4 Br− | +0.85 |
| Hg2+ + 2 e− | ⇌ | Hg(l) | +0.85 |
| [IrCl6]2− + e− | ⇌ | [IrCl6]3− | +0.87 |
| 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 |
| Fe2O3(s) + 6 H+ + 2 e− | ⇌ | 2Fe2+ + 3 H2O | +0.94 |
| MnO2(s) + 4 H+ + e− | ⇌ | Mn3+ + 2 H2O | +0.95 |
| NO3−(aq) + 4 H+ + 3 e− | ⇌ | NO(g) + 2 H2O(l) | +0.958 |
| [AuBr2]− + e− | ⇌ | Au(s) + 2 Br− | +0.96 |
| [HXeO6]3− + 2 H2O + 2 e− | ⇌ | [HXeO4]− + 4 OH− | +0.99 |
| [VO2]+(aq) + 2 H+ + e− | ⇌ | [VO]2+(aq) + H2O | +1.0 |
| H6TeO6(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 |
| Fe3O4(s) + 8 H+ + 2 e− | ⇌ | 3Fe2+ + 4 H2O | +1.09 |
| 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 |
| [HXeO6]3− + 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 |
| 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 |
| [HXeO4]− + 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 |
| 2 NH3OH+ + H+ + 2 e− | ⇌ | N2H5+ + 2 H2O | +1.42 |
| 2 HIO(aq) + 2 H+ + 2 e− | ⇌ | I2(s) + 2 H2O | +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 |
| HClO(aq) + H+ + 2 e− | ⇌ | Cl−(aq) + 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) + 2 H+ + 2 e− | ⇌ | Ni2+ + 2 OH− | +1.59 |
| Ce4+ + e− | ⇌ | Ce3+ | +1.61 |
| 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− + 2 H2O + 3 e− | ⇌ | MnO2(s) + 4 OH− | +1.692 |
| MnO4− + 4 H+ + 3 e− | ⇌ | MnO2(s) + 2 H2O | +1.70 |
| AgO(s) + 2 H+ + e− | ⇌ | Ag+ + H2O | +1.77 |
| 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 |
| HMnO4− + 3 H+ + 2 e− | ⇌ | MnO2(s) + 2 H2O | +2.09 |
| XeO3(aq) + 6 H+ + 6 e− | ⇌ | Xe(g) + 3 H2O | +2.12 |
| H4XeO6(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 |
| H4XeO6(aq) + 2 H+ + 2 e− | ⇌ | XeO3(aq) + 3 H2O | +2.42 |
| F2(g) + 2 e− | ⇌ | 2 F− | +2.87 |
| F2(g) + 2 H+ + 2 e− | ⇌ | 2 HF(aq) | +3.05 |
| KrF2(aq) + 2 e− | ⇌ | Kr(g) + 2 F−(aq) | +3.27 |
