The data below tabulates standard electrode potentials (E°), in volts relative to the standard hydrogen electrode (SHE), at:

Variations from these ideal conditions affect measured voltage via the Nernst equation.

Relationships between Standard Electrode Potentials and Gibbs Free Energy

Electrode potentials of successive elementary half-reactions cannot be directly added. However, the corresponding Gibbs free energy changes (∆G°) can be added. Those free energy changes satisfy

G° = –zFE°,

where z electrons are transferred, and the Faraday constant F is the conversion factor describing coulombs transferred per mole electrons. F = 96 485 C/mol. For example, from

Fe2+(aq) + 2 e ⇌ Fe(s) (−0.44 V),

the energy to form one neutral atom of Fe(s) from one Fe2+(aq) ion and two electrons is 2 × 0.44 eV = 0.88 eV, or 84.907 kJ/(mol e). That value is also the standard formation energy (∆fG°) for an Fe2+(aq) ion, since e and Fe(s) both have zero formation energy.

Data from different sources may cause inconsistencies. For example:

Ti3+
(aq) + eTi2+
(aq) E3→2 = -0.37 V
Ti2+
(aq) + 2 e ⇌ Ti(s) E2→0 = -1.63 V
Ti3+
(aq) + 3 e ⇌ Ti(s) E3→0 = -1.37 V

We can derive an equation relating these electrode potentials:

3 x E3→0 = 1 x E3→2 + 2 x E2→0

This is derived from...

G3→0 = ∆G3→2 + ∆G2→0

...and because ∆G° = –zFE°

Considering the measured values for E3→0, E3→2 and E2→0...

3 x E3→0 = 3 x (-1.37) = -4.11 V
...but 1 x E3→2 + 2 x E2→0 = 1 x (-0.37) + 2 x (-1.63) = -3.63 V ≠ -4.11 V ...

...so there are discrepancies between some of the cited values. A Frost diagram will show the discrepancies clearly.


Table of standard electrode potentials

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

Element Half-reaction
(volt)
Electrons
transferred
Reference
Oxidant Reductant
Sr Sr+
+ e
Sr(s) −4.101 1 [1]
Ca Ca+
+ e
Ca(s) −3.8 1 [1]
Th Th4+
+ e
Th3+
−3.6 1 [2]
Pr Pr3+
+ e
Pr2+
−3.1 1 Estimated[3]
N 3 N
2
(g) + 2 H+ + 2 e
2 HN
3
(aq)
−3.09 2 [4][5]
Li Li+
+ e
Li(s) −3.0401 1 [5][6]:153
N N
2
(g) + 4 H2O + 2 e
2 NH
2
OH
(aq) + 2 OH
−3.04 2 [4]
Cs Cs+
+ e
Cs(s) −3.026 1 [5]
Ca Ca(OH)
2
+ 2 e
Ca(s) + 2 OH −3.02 2 [1]
Er Er3+
+ e
Er2+
−3 1 [1]
Ba Ba(OH)
2
+ 2 e
Ba(s) + 2 OH −2.99 2 [1]
Rb Rb+
+ e
Rb(s) −2.98 1 [5]
K K+
+ e
K(s) −2.931 1 [5]
Ba Ba2+
+ 2 e
Ba(s) −2.912 2 [5]
La La(OH)
3
(s) + 3 e
La(s) + 3 OH −2.9 3 [5]
Fr Fr+
+ e
Fr(s) −2.9 1 [1]
Sr Sr2+
+ 2 e
Sr(s) −2.899 2 [5]
Sr Sr(OH)
2
+ 2 e
Sr(s) + 2 OH −2.88 2 [1]
Ca Ca2+
+ 2 e
Ca(s) −2.868 2 [5][6]:153
Li Li+
+ C
6
(s) + e
LiC
6
(s)
−2.84 1 [5]
Eu Eu2+
+ 2 e
Eu(s) −2.812 2 [5]
Ra Ra2+
+ 2 e
Ra(s) −2.8 2 [5]
Ho Ho3+
+ e
Ho2+ −2.8 1 [1]
Bk Bk3+
+ e
Bk2+
−2.8 1 [1]
Yb Yb2+
+ 2 e
Yb(s) −2.76 2 [1]
Na Na+
+ e
Na(s) −2.71 1 [5][7]
Mg Mg+
+ e
Mg(s) −2.7 1 [1]
Nd Nd3+
+ e
Nd2+
−2.7 1 [1]
Mg Mg(OH)
2
+ 2 e
Mg(s) + 2 OH −2.69 2 [1]
Sm Sm2+
+ 2 e
Sm(s) −2.68 2 [1]
Be Be2O32– + 3 H2O + 4 e 2 Be(s) + 6 OH −2.63 4 [1]
Pm Pm3+
+ e
Pm2+
−2.6 1 [1]
Dy Dy3+
+ e
Dy2+
−2.6 1 [1]
No No2+
+ 2 e
No(s) −2.5 2 [1]
Hf HfO(OH)
2
+ H2O + 4 e
Hf(s) + 4 OH −2.5 4 [1]
Th Th(OH)
4
+ 4 e
Th(s) + 4 OH −2.48 4 [1]
Md Md2+
+ 2 e
Md(s) −2.4 2 [1]
Tm Tm2+
+ 2 e
Tm(s) −2.4 2 [1]
La La3+
+ 3 e
La(s) −2.379 3 [5]
Y Y3+
+ 3 e
Y(s) −2.372 3 [5]
Mg Mg2+
+ 2 e
Mg(s) −2.372 2 [5]
Sc ScF3(aq) + 3 H+ + 3 e Sc(s) + 3 HF(aq) −2.37 3 [6]:792
Zr ZrO(OH)
2
(s) + H2O + 4 e
Zr(s) + 4 OH −2.36 4 [5]
Pr Pr3+
+ 3 e
Pr(s) −2.353 3 [1]
Ce Ce3+
+ 3 e
Ce(s) −2.336 3 [1]
Er Er3+
+ 3 e
Er(s) −2.331 3 [1]
Ho Ho3+
+ 3 e
Ho(s) −2.33 3 [1]
Al H2AlO3 + H2O + 3 e Al(s) + 4 OH −2.33 3 [1]
Nd Nd3+
+ 3 e
Nd(s) −2.323 3 [1]
Tm Tm3+
+ 3 e
Tm(s) −2.319 3 [1]
Al Al(OH)
3
(s) + 3 e
Al(s) + 3 OH −2.31 3 [8]
Sm Sm3+
+ 3 e
Sm(s) −2.304 3 [1]
Fm Fm2+ + 2 e Fm(s) −2.3 2 [1]
Am Am3+
+ e
Am2+
−2.3 1 [1]
Dy Dy3+
+ 3 e
Dy(s) −2.295 3 [1]
Lu Lu3+
+ 3 e
Lu(s) −2.28 3 [1]
Sc ScF2+ + 2 H+ + 3 e Sc(s) + 2 HF(l) −2.28 3 [6]:792
Tb Tb3+
+ 3 e
Tb(s) −2.28 3 [1]
Gd Gd3+
+ 3 e
Gd(s) −2.279 3 [1]
H H
2
(g) + 2 e
2 H
−2.23 2 [1]
Es Es2+
+ 2 e
Es(s) −2.23 2 [1]
Pm Pm2+
+ 2 e
Pm(s) −2.2 2 [1]
Tm Tm3+
+ e
Tm2+ −2.2 1 [1]
Dy Dy2+
+ 2 e
Dy(s) −2.2 2 [1]
Ac Ac3+
+ 3 e
Ac(s) −2.2 3 [1]
Yb Yb3+
+ 3 e
Yb(s) −2.19 3 [1]
Cf Cf2+
+ 2 e
Cf(s) −2.12 2 [1]
Nd Nd2+
+ 2 e
Nd(s) −2.1 2 [1]
Ho Ho2+
+ 2 e
Ho(s) −2.1 2 [1]
Sc Sc3+
+ 3 e
Sc(s) −2.077 3 [9]
Al AlF63– + 3 e Al(s) + 6 F
−2.069 3 [1]
Cm Cm3+
+ 3 e
Cm(s) −2.04 3 [1]
Pu Pu3+
+ 3 e
Pu(s) −2.031 3 [1]
Pr Pr2+
+ 2 e
Pr(s) −2 2 [1]
Er Er2+
+ 2 e
Er(s) −2 2 [1]
Eu Eu3+
+ 3 e
Eu(s) −1.991 3 [1]
Lr Lr3+
+ 3 e
Lr(s) −1.96 3 [1]
Cf Cf3+
+ 3 e
Cf(s) −1.94 3 [1]
Es Es3+
+ 3 e
Es(s) −1.91 3 [1]
Pa Pa4+
+ e
Pa3+
−1.9 1 [1]
Am Am2+
+ 2 e
Am(s) −1.9 2 [1]
Th Th4+
+ 4 e
Th(s) −1.899 4 [1]
Fm Fm3+
+ 3 e
Fm(s) −1.89 3 [1]
N N2(g) + 2 H2O(l) + 4 H+ + 2 e 2 NH3OH+ −1.87 2 [6]:789
Np Np3+
+ 3 e
Np(s) −1.856 3 [1]
Be Be2+
+ 2 e
Be(s) −1.847 2 [1]
P H2PO2 + e P(s) + 2 OH −1.82 1 [1]
U U3+
+ 3 e
U(s) −1.798 3 [1]
Sr Sr2+
+ 2 e
Sr(Hg) −1.793 2 [1]
B H2BO3 + H2O + 3 e B(s) + 4 OH −1.79 3 [1]
Th ThO
2
+ 4 H+ + 4 e
Th(s) + 2 H2O −1.789 4 [1]
Hf HfO2+
+ 2 H+ + 4 e
Hf(s) + H2O −1.724 4 [1]
P HPO32– + 2 H2O + 3 e P(s) + 5 OH −1.71 3 [1]
Si SiO32– + 3 H2O + 4 e Si(s) + 6 OH −1.697 4 [1]
Al Al3+
+ 3 e
Al(s) −1.662 3 [1]
Ti Ti2+
+ 2 e
Ti(s) −1.63 2 [7]
Zr ZrO
2
(s) + 4 H+ + 4 e
Zr(s) + 2 H2O −1.553 4 [10]
Zr Zr4+
+ 4 e
Zr(s) −1.45 4 [10]
Ti Ti3+
+ 3 e
Ti(s) −1.37 3 [11]
Ti TiO(s) + 2 H+ + 2 e Ti(s) + H2O −1.31 2 [6]:792
B [B(OH)4] + 4 H2O(l) + 8 e BH4 + 8 OH −1.24 8 [6]:788
Ti Ti
2
O
3
(s) + 2 H+ + 2 e
2 TiO(s) + H2O −1.23 2 [6]:792
Ga [Ga(OH)4] + 3 e Ga(s) + 3 OH −1.22 3 [6]:788
Zn [Zn(OH)4]2– + 2 e Zn(s) + 4 OH −1.199 2 [10]
Mn Mn2+
+ 2 e
Mn(s) −1.185 2 [10]
Fe [Fe(CN)6]4− + 6 H+ + 2 e Fe(s) + 6 HCN(aq) −1.16 2 [12]
C C(s) + 3 H2O(l) + 2 e CH3OH(l) + 2 OH −1.148 2 [6]:788
Cr [Cr(CN)6]3– + e [Cr(CN)6]4– −1.143 1 [6]:793
Te Te(s) + 2 e Te2−
−1.143 2 [13]
V V2+
+ 2 e
V(s) −1.13 2 [13]
Nb Nb3+
+ 3 e
Nb(s) −1.099 3 [8]
Sn Sn(s) + 4 H+ + 4 e SnH
4
(g)
−1.07 4
Po Po(s) + 2 e Po2−
−1.021 2 [14]
Cr [Cr(edta)(H2O)] + e [Cr(edta)(H2O)]2 −0.99 1 [6]:793
P 2 H3PO4(aq) + 2 H+ + 2 e (H2PO3)2(aq) + H2O(l) −0.933 2 [6]:789
C CO32– + 3 H+ + 2 e HCO2 + H2O(l) −0.93 2 [6]:788
Ti TiO2+
+ 2 H+ + 4 e
Ti(s) + H2O −0.93 4
Si SiO
2
(quartz) + 4 H+ + 4 e
Si(s) + 2 H2O −0.909 4 [6]:788
Cr Cr2+
+ 2 e
Cr(s) −0.9 2 [6]:793
B B(OH)
3
(aq) + 3 H+ + 3 e
B(s) + 3 H2O −0.89 3 [6]:788
Fe Fe(OH)
2
(s) + 2 e
Fe(s) + 2 OH −0.89 2 [12]
Fe Fe
2
O
3
(s) + 3 H2O + 2 e
2 Fe(OH)
2
(s) + 2 OH
−0.86 2 [12]
H 2 H2O + 2 e H
2
(g) + 2 OH
−0.8277 2 [10]
Bi Bi(s) + 3 H+ + 3 e BiH
3
−0.8 3 [10]
Zn Zn2+
+ 2 e
Zn(Hg) −0.7628 2 [10]
Zn Zn2+
+ 2 e
Zn(s) −0.7618 2 [10]
Ta Ta
2
O
5
(s) + 10 H+ + 10 e
2 Ta(s) + 5 H2O −0.75 10
Cr Cr3+
+ 3 e
Cr(s) −0.74 3 [7]
Te 2 Te(s) + 2 e Te22– −0.74 2 [6]:790
Ni Ni(OH)
2
(s) + 2 e
Ni(s) + 2 OH −0.72 2 [1]
Nb Nb
2
O
5
(s) + 10 H+ + 10 e
2 Nb(s) + 5 H2O(l) −0.7 10 [6]:793
Ag Ag
2
S
(s) + 2 e
2Ag(s) + S2−
−0.69 2
Te Te22– + 4 H+ + 2 e 2 H2Te(g) −0.64 2 [6]:790
Sb [Sb(OH)4] + 3 e Sb(s) + 4 OH −0.639 3 [6]:789
Au [Au(CN)2] + e Au(s) + 2 CN
−0.6 1
Ta Ta3+
+ 3 e
Ta(s) −0.6 3 [8]
Pb PbO(s) + H2O + 2 e Pb(s) + 2 OH −0.580 2 [8]
Ti 2 TiO
2
(s) + 2 H+ + 2 e
Ti
2
O
3
(s) + H2O
−0.56 2 [6]:792
Ga Ga3+
+ 3 e
Ga(s) −0.549 3 [8]
U U4+
+ e
U3+
−0.52 1 [15]
P H
3
PO
2
(aq) + H+ + e
P(white)[note 1] + 2 H2O −0.508 1 [10]
P H
3
PO
3
(aq) + 2 H+ + 2 e
H
3
PO
2
(aq) + H2O
−0.499 2 [10]
Ni NiO
2
(s) + 2 H2O + 2 e
Ni(OH)
2
(s) + 2 OH
−0.49 2 [1]
Sb [Sb(OH)6] + 2 e [Sb(OH)4] + 2 OH −0.465 2 [6]:789
P H
3
PO
3
(aq) + 3 H+ + 3 e
P(red)[note 1] + 3 H2O −0.454 3 [10]
Bi Bi2O3(s) + 3 H2O(l) + 6 e Bi(s) + 6 OH −0.452 6 [6]:789
Ta TaF72– + 7 H+ + 5 e Ta(s) + 7 HF(l) −0.45 5 [6]:793
In In3+
+ 2 e
In+ −0.444 2 [6]:788
Cu [Cu(CN)2] + e Cu(s) + 2 CN
−0.44 1 [13]
Fe Fe2+
+ 2 e
Fe(s) −0.44 2 [7]
C 2 CO
2
(g) + 2 H+ + 2 e
HOOCCOOH(aq) −0.43 2
Cr Cr3+
+ e
Cr2+
−0.407 1 [8]
Cd Cd2+
+ 2 e
Cd(s) −0.4 2 [8]
Ti Ti3+
+ e
Ti2+
−0.37 1 [6]:792
Cu Cu
2
O
(s) + H2O + 2 e
2 Cu(s) + 2 OH −0.36 2 [10]
Pb PbSO
4
(s) + 2 e
Pb(s) + SO42− −0.3588 2 [10]
Pb PbSO
4
(s) + 2 e
Pb(Hg) + SO42− −0.3505 2 [10]
Eu Eu3+
+ e
Eu2+
−0.35 1 [15]
In In3+
+ 3 e
In(s) −0.34 3 [13]
Tl Tl+
+ e
Tl(s) −0.34 1 [13]
Ge Ge(s) + 4 H+ + 4 e GeH
4
(g)
−0.29 4
Co Co2+
+ 2 e
Co(s) −0.28 2 [10]
P H
3
PO
4
(aq) + 2 H+ + 2 e
H
3
PO
3
(aq) + H2O
−0.276 2 [10]
N N2(g) + 8 H+ + 6 e 2 NH4+ 0.27 6 [16]
V V3+
+ e
V2+
−0.26 1 [7]
Ni Ni2+
+ 2 e
Ni(s) −0.257 2 [8]
S 2 HSO4 + 2 H+ + 2 e S2O62– + 2 H2O(l) −0.253 2 [6]:790
As As(s) + 3 H+ + 3 e AsH
3
(g)
−0.23 3 [13]
N N2(g) + 5 H+ + 4 e N2H5+ −0.23 4 [6]:789
Ga Ga+
+ e
Ga(s) −0.2 1 [8]
Ag AgI(s) + e Ag(s) + I
−0.15224 1 [10]
Ge GeO2(s) + 4 H+ + 4 e Ge(s) + 2 H2O(l) −0.15 4 [16]
Mo MoO
2
(s) + 4 H+ + 4 e
Mo(s) + 2 H2O −0.15 4
Si Si(s) + 4 H+ + 4 e SiH
4
(g)
−0.14 4
Sn Sn2+
+ 2 e
Sn(s) −0.13 2
O O
2
(g) + H+ + e
HO
2
(aq)
−0.13 1
In In+ + e In(s) −0.126 1 [6]:788
Pb Pb2+
+ 2 e
Pb(s) −0.126 2 [7]
W WO
2
(s) + 4 H+ + 4 e
W(s) + 2 H2O −0.12 4
Ge GeO
2
(s) + 2 H+ + 2 e
GeO(s) + H2O −0.118 2 [8]
P P(red) + 3 H+ + 3 e PH
3
(g)
−0.111 3 [10]
C CO
2
(g) + 2 H+ + 2 e
HCOOH(aq) −0.11 2
Se Se(s) + 2 H+ + 2 e H
2
Se
(g)
−0.11 2 [6]:790
C CO
2
(g) + 2 H+ + 2 e
CO(g) + H2O −0.11 2
Sn α-SnO(s) + 2 H+ + 2 e Sn(s) + H2O −0.104 2 [6]:788
Cu [Cu(NH3)2]+ + e Cu(s) + 2 NH
3
(aq)
−0.1 1 [13]
Nb Nb2O5(s) + 10 H+ + 4 e 2 Nb3+
+ 5 H2O(l)
−0.1 4 [6]:793
W WO
3
(aq) + 6 H+ + 6 e
W(s) + 3 H2O −0.09 6 [13]
Sn SnO
2
(s) + 2 H+ + 2 e
α-SnO(s) + H2O −0.088 2 [6]:788
Fe Fe
3
O
4
(s) + 8 H+ + 8 e
3 Fe(s) + 4 H2O −0.085 8 [17]
V VOH2+
+ H+ + e
V2+
+ H2O(l)
−0.082 1 [6]:793
P P(white) + 3 H+ + 3 e PH
3
(g)
−0.063 3 [10]
N N2O(g) + H2O(l) + 6 H+ + 4 e 2 NH3OH+ −0.05 4 [6]:789
Fe Fe3+
+ 3 e
Fe(s) −0.04 3 [12]
C HCOOH(aq) + 2 H+ + 2 e HCHO(aq) + H2O −0.034 2 [6]:788
H 2 H+ + 2 e H
2
(g)
0 2
Ag AgBr(s) + e Ag(s) + Br
0.07133 1 [10]
S S4O62− + 2 e 2 S2O32− 0.08 2
N N
2
(g) + 2 H2O + 6 H+ + 6 e
2 NH
4
OH
(aq)
0.092 6
Hg HgO(s) + H2O + 2 e Hg(l) + 2 OH 0.0977 2
Cu [Cu(NH3)4]2+ + e [Cu(NH3)2]+ + 2 NH
3
(aq)
0.1 1 [13]
Ru [Ru(NH3)6]3+ + e [Ru(NH3)6]2+ 0.1 1 [15]
N N
2
H
4
(aq) + 4 H2O + 2 e
2 NH4+ + 4 OH 0.11 2 [4]
Mo H
2
MoO
4
(aq) + 6 H+ + 6 e
Mo(s) + 4 H2O 0.11 6
Ge Ge4+
+ 4 e
Ge(s) 0.12 4
C C(s) + 4 H+ + 4 e CH
4
(g)
0.13 4 [13]
C HCHO(aq) + 2 H+ + 2 e CH
3
OH
(aq)
0.13 2
S S(s) + 2 H+ + 2 e H
2
S
(g)
0.144 2 [6]:790
Sb Sb2O3(s) + 6 H+ + 6 e 2 Sb(s) + 3 H2O 0.15 6 [6]:789
Sn Sn4+
+ 2 e
Sn2+
0.151 2 [8]
S HSO4 + 3 H+ + 2 e SO
2
(aq) + 2 H2O
0.158 2 [6]:790
Cu Cu2+
+ e
Cu+
0.159 1 [13]
U UO22+ + e UO2+ 0.163 1 [15]
S SO42– + 4 H+ + 2 e SO
2
(aq) + 2 H2O
0.17 2
Ti TiO2+
+ 2 H+ + e
Ti3+
+ H2O
0.19 1
Sb SbO+
+ 2 H+ + 3 e
Sb(s) + H2O 0.2 3
Fe 3 Fe
2
O
3
(s) + 2 H+ + 2 e
2 Fe
3
O
4
(s) + H2O
0.22 2 [18]:p.100
Ag AgCl(s) + e Ag(s) + Cl
0.22233 1 [10]
As H
3
AsO
3
(aq) + 3 H+ + 3 e
As(s) + 3 H2O 0.24 3 [6]:789
Ru Ru3+
+ e
Ru2+
0.249 1 [19]
Pb PbO2(s) + H2O + 2 e α-PbO(s) + 2 OH 0.254 2 [6]:788
Ge GeO(s) + 2 H+ + 2 e Ge(s) + H2O 0.26 2
Hg Hg2Cl2(s) + 2 e 2 Hg(l) + 2 Cl 0.27 2 [16]
U UO2+ + 4 H+ + e U4+
+ 2 H2O
0.273 1 [15]
At At + e At 0.3 1 [20]
Bi Bi3+
+ 3 e
Bi(s) 0.308 3 [10]
C 2 HCNO + 2 H+ + 2 e (CN)2 + 2 H2O 0.330 2 [8]
Cu Cu2+
+ 2 e
Cu(s) 0.337 2 [13]
V VO2+
+ 2 H+ + e
V3+
+ H2O
0.337 1 [6]:793
Sb Sb2O4(s) + 2 H+ + 2 e Sb2O3(s) + H2O(l) 0.342 2 [6]:789
At At+ + 2 e At 0.36 2 [21]
Fe [Fe(CN)6]3– + e [Fe(CN)6]4– 0.3704 1 [22]
C (CN)2 + 2 H+ + 2 e 2 HCN 0.373 2 [8]
P (H2PO3)2(aq) + 2 H+ + 2 e 2 H3PO3 0.38 2 [6]:789
S 2 SO2(aq) + 2 H+ + 2 e S2O32– + H2O(l) 0.4 2 [6]:790
O O
2
(g) + 2 H2O + 4 e
4 OH 0.401 4 [7]
Mo H
2
MoO
4
+ 6 H+ + 3 e
Mo3+
+ 4 H2O
0.43 3
Ru Ru2+
+ 2 e
Ru(s) 0.455 2 [19]
V VO(OH)+ + 2 H+ + e VOH2+
+ H2O(l)
0.481 1 [6]:793
Re Re3+
+ 3 e
Re(s) 0.5 3 [3]
C CH
3
OH
(aq) + 2 H+ + 2 e
CH
4
(g) + H2O
0.5 2
S SO
2
(aq) + 4 H+ + 4 e
S(s) + 2 H2O 0.5 4 [6]:790
S 4 SO
2
(aq) + 4 H+ + 6 e
S4O62– + 2 H2O(l) 0.51 6 [16]
Cu Cu+
+ e
Cu(s) 0.52 1 [13]
C CO(g) + 2 H+ + 2 e C(s) + H2O 0.52 2 [6]:788
I I3 + 2 e 3 I
0.53 2 [7]
Te TeO2(s) + 4 H+ + 4 e Te(s) + 2 H2O(l) 0.53 4 [6]:790
Cu Cu2+
+ Cl + e
CuCl(s) 0.54 1 [16]
I I
2
(s) + 2 e
2 I
0.54 2 [7]
Au AuI4 + 3 e Au(s) + 4 I
0.56 3
As H
3
AsO
4
(aq) + 2 H+ + 2 e
H
3
AsO
3
(aq) + H2O
0.56 2 [6]:789
S S2O62– + 4 H+ + 2 e 2 H2SO3 0.569 2 [6]:790
Au AuI2 + e Au(s) + 2 I
0.58 1
Mn MnO4 + 2 H2O + 3 e MnO
2
(s) + 4 OH
0.595 3 [1]
S S2O32– + 6 H+ + 4 e 2 S(s) + 3 H2O 0.6 4 [6]:790
Fe Fc+
+ e
Fc(s) 0.63 1 Substantial literature variation[23]
Mo H
2
MoO
4
(aq) + 2 H+ + 2 e
MoO
2
(s) + 2 H2O
0.65 2
N HN3(aq) + 11 H+ + 8 e 3 NH4+ 0.69 8 [16]
O O
2
(g) + 2 H+ + 2 e
H
2
O
2
(aq)
0.695 2 [8]
Sb Sb2O5(s) + 4 H+ + 4 e Sb2O3(s) + 2 H2O 0.699 4 [6]:789
C + 2 H+ + 2 e 0.6992 2 [10]
V H2V10O284– + 24 H+ + 10 e 10 VO(OH)+ + 8 H2O(l) 0.723 10 [6]:793
Pt PtCl62– + 2 e PtCl42– + 2 Cl
0.726 2 [15]
Fe Fe
2
O
3
(s) + 6 H+ + 2 e
2 Fe2+
+ 3 H2O
0.728 2 [18]:p.100
Se H
2
SeO
3
(aq) + 4 H+ + 4 e
Se(s) + 3 H2O 0.74 4 [8]
At AtO+ + 2 H+ + 2 e At+ + H2O 0.74 2 [21]
Tl Tl3+
+ 3 e
Tl(s) 0.741 3 [8]
No No3+
+ e
No2+
0.75 1 [24]
Pt PtCl42– + 2 e Pt(s) + 4 Cl
0.758 2 [15]
Br BrO + H2O(l) + 2 e Br + 2 OH 0.76 2 [6]:791
Po Po4+ + 4 e Po(s) 0.76 4 [8]
S (SCN)2 + 2 e 2 SCN 0.769 2 [25][8]
Fe Fe3+
+ e
Fe2+
0.771 1 [8]
Hg Hg22+ + 2 e 2 Hg(l) 0.7973 2 [8]
Ag Ag+
+ e
Ag(s) 0.7996 1 [10]
N 2 NO3 + 4 H+ + 2 e N
2
O
4
(g) + 2 H2O
0.803 2 [6]:789
Fe 2 FeO42– + 5 H2O + 6 e Fe
2
O
3
(s) + 10 OH
0.81 6 [12]
Au AuBr4 + 3 e Au(s) + 4 Br
0.85 3
Hg Hg2+
+ 2 e
Hg(l) 0.85 2
Ir IrCl62– + e IrCl63– 0.87 1 [6]:153
Mn MnO4 + H+ + e HMnO4 0.9 1
Po Po4+ + 2 e Po2+ 0.9 2 [8]
Hg 2 Hg2+
+ 2 e
Hg2+
2
0.91 2 [13]
Pd Pd2+
+ 2 e
Pd(s) 0.915 2 [15]
Au AuCl4 + 3 e Au(s) + 4 Cl
0.93 3
N NO3 + 3 H+ + 2 e HNO2(aq) 0.94 2 [6]:789
Mn MnO
2
(s) + 4 H+ + e
Mn3+
+ 2 H2O
0.95 1
N NO3 + 4 H+ + 3 e NO(g) + 2 H2O(l) 0.958 3 [7]
Au AuBr2 + e Au(s) + 2 Br
0.96 1
Fe Fe
3
O
4
(s) + 8 H+ + 2 e
3 Fe2+
+ 4 H2O
0.98 2 [18]:p.100
Xe HXeO63– + 2 H2O + 2 e HXeO4 + 4 OH 0.99 2 [6]:792[26]
N HNO2(aq) + H+ + e NO(g) + H2O(l) 0.996 1 [6]:789
At HAtO + H+ + e At + H2O 1.0 1 [20]
V VO+
2
+ 2 H+ + e
VO2+
+ H2O
1 1 [27]
Te H
6
TeO
6
(aq) + 2 H+ + 2 e
TeO
2
(s) + 4 H2O
1.02 2 [27]
N NO2(g) + 2 H+ + 2 e NO(g) + H2O(l) 1.03 2 [16]
Br Br3 + 2 e 3 Br
1.05 2 [16]
Sb Sb2O5(s) + 2 H+ + 2 e Sb2O4(s) + H2O(l) 1.055 2 [6]:789
I ICl2 + e 2 Cl
+ I(s)
1.06 1 [16]
Br Br
2
(l) + 2 e
2 Br
1.066 2 [10]
N N2O4(g) + 2 H+ + 2 e 2 HNO2 1.07 2 [6]:789
Br Br
2
(aq) + 2 e
2 Br
1.0873 2 [10]
Ru RuO
2
+ 4 H+ + 2 e
Ru2+
+ 2 H2O
1.120 2 [19]
Cu Cu2+
+ 2 CN
+ e
Cu(CN)2 1.12 1 [13]
I IO3 + 5 H+ + 4 e HIO(aq) + 2 H2O 1.13 4 [6]:791
O H2O2(aq) + H+ + e H2O(l) + HO• 1.14 1 [6]:790
Au AuCl2 + e Au(s) + 2 Cl
1.15 1
Se HSeO4 + 3 H+ + 2 e H
2
SeO
3
(aq) + H2O
1.15 2 [6]:790
Ag Ag
2
O
(s) + 2 H+ + 2 e
2 Ag(s) + H2O 1.17 2
Cl ClO3 + 2 H+ + e ClO
2
(g) + H2O
1.175 1 [6]:791
Xe HXeO63– + 5 H2O + 8 e Xe(g) + 11 OH 1.18 8 [26]
Pt Pt2+
+ 2 e
Pt(s) 1.188 2 [15]
Cl ClO
2
(g) + H+ + e
HClO
2
(aq)
1.19 1 [28]
I 2 IO3 + 12 H+ + 10 e I
2
(s) + 6 H2O
1.2 10 [16]
Mn MnO
2
(s) + 4 H+ + 2 e
Mn2+
+ 2 H2O
1.224 2 [10]
O O
2
(g) + 4 H+ + 4 e
2 H2O 1.229 4 [7]
N N2H5+ + 3 H+ + 2 e 2 NH4+ 1.28 2 [6]:789
Cl ClO4 + 2 H+ + 2 e ClO3 + H2O 1.23 2 [29]
Ru [Ru(bipy)
3
]3+
+ e
[Ru(bipy)
3
]2+
1.24 1 [1]
Xe HXeO4 + 3 H2O + 6 e Xe(g) + 7 OH 1.24 6 [6]:792[26]
N 2 NO3 + 12 H+ + 10 e N2(g) + 6 H2O(l) 1.25 10 [6]:789
Tl Tl3+
+ 2 e
Tl+
1.25 2 [6]:788
N 2 HNO2(aq) + 4 H+ + 4 e N2O(g) + 3 H2O(l) 1.297 4 [6]:789
Cr Cr2O72− + 14 H+ + 6 e 2 Cr3+
+ 7 H2O
1.33 6 [4]:1005
N NH3OH+ + 2 H+ + 2 e NH4+ + H2O(l) 1.35 2 [6]:789
Cl Cl
2
(g) + 2 e
2 Cl
1.36 2 [7]
Ru RuO4 + 8 H+ + 5 e Ru2+
+ 4 H2O
1.368 5 [19]
Ru RuO
4
+ 4 H+ + 4 e
RuO
2
+ 2 H2O
1.387 4 [19]
Co CoO
2
(s) + 4 H+ + e
Co3+
+ 2 H2O
1.42 1
N 2 NH
3
OH+
+ H+ + 2 e
N2H5+ + 2 H2O 1.42 2 [4]
I 2 HIO(aq) + 2 H+ + 2 e I
2
(s) + 2 H2O
1.44 2 [6]:791
Br BrO3 + 5 H+ + 4 e HBrO(aq) + 2 H2O 1.447 4 [6]:791
Pb β-PbO
2
(s) + 4 H+ + 2 e
Pb2+
+ 2 H2O
1.46 2 [13]
Pb α-PbO
2
(s) + 4 H+ + 2 e
Pb2+
+ 2 H2O
1.468 2 [13]
Br 2 BrO3 + 12 H+ + 10 e Br
2
(l) + 6 H2O
1.48 10
At HAtO3 + 4 H+ + 4 e HAtO + 2 H2O 1.5 4 [20]
Mn MnO4 + 8 H+ + 5 e Mn2+
+ 4 H2O
1.51 5 [16]
O HO
2
+ H+ + e
H
2
O
2
(aq)
1.51 1
Au Au3+
+ 3 e
Au(s) 1.52 3
Ru RuO42– + 8 H+ + 4 e Ru2+
+ 4 H2O
1.563 4 [19]
N 2 NO(g) + 2 H+ + 2 e N2O(g) + H2O(l) 1.59 2 [6]:789
Ni NiO
2
(s) + 2 H+ + 2 e
Ni2+
+ 2 OH
1.59 2
Ce Ce4+
+ e
Ce3+
1.61 1
Cl 2 HClO(aq) + 2 H+ + 2 e Cl
2
(g) + 2 H2O
1.63 2 [28]
I IO4 + 2 H+ + 2 e IO3 + H2O 1.64 2 [29]
Ag Ag
2
O
3
(s) + 6 H+ + 4 e
2 Ag+
+ 3 H2O
1.67 4
Cl HClO
2
(aq) + 2 H+ + 2 e
HClO(aq) + H2O 1.67 2 [28]
Pb Pb4+
+ 2 e
Pb2+
1.69 2 [13]
Mn MnO4 + 4 H+ + 3 e MnO
2
(s) + 2 H2O
1.7 3 [16]
Br BrO4 + 2 H+ + 2 e BrO3 + H2O 1.74 2 [29]
Ag AgO(s) + 2 H+ + e Ag+
+ H2O
1.77 1
N N2O(g) + 2 H+ + 2 e N2(g) + H2O(l) 1.77 2 [6]:789
O H
2
O
2
(aq) + 2 H+ + 2 e
2 H2O 1.78 2 [28]
Au Au+
+ e
Au(s) 1.83 1 [13]
Co Co3+
+ e
Co2+
1.92 1 [8]
Ag Ag2+
+ e
Ag+
1.98 1 [13]
O S2O82– + 2 e 2 SO42– 2.01 2 [10]
O O
3
(g) + 2 H+ + 2 e
O
2
(g) + H2O
2.075 2 [15]
Mn HMnO4 + 3 H+ + 2 e MnO
2
(s) + 2 H2O
2.09 2
Xe XeO
3
(aq) + 6 H+ + 6 e
Xe(g) + 3 H2O 2.12 6 [6]:792[26]
Xe H
4
XeO
6
(aq) + 8 H+ + 8 e
Xe(g) + 6 H2O 2.18 8 [6]:792[26]
Fe FeO42− + 8 H+ + 3 e Fe3+
+ 4 H2O
2.2 3 [30]
Xe XeF
2
(aq) + 2 H+ + 2 e
Xe(g) + 2 HF(aq) 2.32 2 [26][28]
O HO• + H+ + e H2O(l) 2.38 1 [6]:790
Xe H
4
XeO
6
(aq) + 2 H+ + 2 e
XeO
3
(aq) + 3 H2O
2.42 2 [26][6]:792
F F
2
(g) + 2 e
2 F
2.87 2 [6]:153[7][13]
Cm Cm4+ + e Cm3+ 3.0 1 Estimated[3]
F F
2
(g) + 2 H+ + 2 e
2 HF(aq) 3.077 2 [3]
Tb Tb4+ + e Tb3+ 3.1 1 Estimated[3]
Pr Pr4+ + e Pr3+ 3.2 1 Estimated[3]
Kr KrF
2
(aq) + 2 e
Kr(g) + 2 F
3.27 2 Estimated[31]

See also

Notes

  1. 1 2 Not specified in the indicated reference, but assumed due to the difference between the value −0.454 and that computed by (2×(−0.499) + (−0.508))/3 = −0.502, exactly matching the difference between the values for white (−0.063) and red (−0.111) phosphorus in equilibrium with PH3.

References

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