Standard electrode potential (data page)

Main article: Standard electrode potential

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

• Temperature 298.15 K (25.00 °C; 77.00 °F);
• Effective concentration (activity) 1 mol/L for each aqueous or amalgamated (mercury-alloyed) species;
• Unit activity for each solvent and pure solid or liquid species; and
• Absolute partial pressure 101.325 kPa (1.00000 atm; 1.01325 bar) for each gaseous reagent — the convention in most literature data but not the current standard state (100 kPa).

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

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

∆G° = –zFE°,

where z electrons are transferred, and the Faraday constant F is the conversion factor describing Coulombs transferred per mole electrons. Those Gibbs free energy changes can be added.

For example, from Fe²⁺ + 2 e⁻ ⇌ Fe(s) (−0.44 V), the energy to form one neutral atom of Fe(s) from one Fe²⁺ ion and two electrons is 2 × 0.44 eV = 0.88 eV, or 84 907 J/(mol  e⁻). That value is also the standard formation energy (∆G_f°) for an Fe²⁺ ion, since  e⁻ and Fe(s) both have zero formation energy.

Data from different sources may cause table inconsistencies. For example: $${\displaystyle {\begin{alignedat}{4}&{\ce {Cu+ + e-}}&{}\rightleftharpoons {}&{\ce {Cu(s)}}&\quad \quad E_{1}=+0.520{\text{ V}}\\&{\ce {Cu^2+ + 2e-}}&{}\rightleftharpoons {}&{\ce {Cu(s)}}&\quad \quad E_{2}=+0.337{\text{ V}}\\&{\ce {Cu^2+ + e-}}&{}\rightleftharpoons {}&{\ce {Cu+}}&\quad \quad E_{3}=+0.159{\text{ V}}\end{alignedat}}}$$ From additivity of Gibbs energies, one must have $${\displaystyle 2\cdot E_{2}=1\cdot E_{1}+1\cdot E_{3}}$$ But that equation does not hold exactly with the cited values.

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			E° (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	3N 2(g) + 2 H+ + 2 e−	⇌	2HN 3(aq)	−3.09	2	[4][5]
Li	Li+ +  e−	⇌	Li(s)	−3.0401	1	[5][6]: 153
N	N 2(g) + 4H2O + 2 e−	⇌	2NH 2OH(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	Be 2O2− 3 + 3H2O + 4 e−	⇌	2Be(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	−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	−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) + 3HF(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	H 2AlO− 3 + 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	−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	ScF+ 2 + 2 H+ + 3 e−	⇌	Sc(s) + 2HF(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−	⇌	2H−	−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	AlF3− 6 + 3 e−	⇌	Al(s) + 6F−	−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	−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	−1.89	3	[1]
N	N2(g) + 2H2O(l) + 4 H+ + 2 e−	⇌	2NH3OH+	−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	H 2PO− 2 +  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	H 2BO− 3 + H2O + 3 e−	⇌	B(s) + 4 OH−	−1.79	3	[1]
Th	ThO 2 + 4 H+ + 4 e−	⇌	Th(s) + 2H2O	−1.789	4	[1]
Hf	HfO2+ + 2 H+ + 4 e−	⇌	Hf(s) + H2O	−1.724	4	[1]
P	HPO2− 3 + 2H2O + 3 e−	⇌	P(s) + 5 OH−	−1.71	3	[1]
Si	SiO2− 3 + 3H2O + 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) + 2H2O	−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 + 4H2O(l) + 8 e−	⇌	BH− 4 + 8 OH−	−1.24	8	[6]: 788
Ga	GaO(OH)− 2 + H2O(l) + 3 e−	⇌	Ga(s) + 3 OH−	−1.22	3	[6]: 788
Ti	Ti 2O 3(s) + 2 H+ + 2 e−	⇌	2TiO(s) + H2O	−1.23	2	[6]: 792
Zn	Zn(OH)2− 4 + 2 e−	⇌	Zn(s) + 4 OH−	−1.199	2	[10]
Mn	Mn2+ + 2 e−	⇌	Mn(s)	−1.185	2	[10]
Fe	Fe(CN)4− 6 + 6 H+ + 2 e−	⇌	Fe(s) + 6HCN(aq)	−1.16	2	[12]
C	C(s) + 3H2O(l) + 2 e−	⇌	CH3OH(l) + 2 OH−	−1.148	2	[6]: 788
Cr	Cr(CN)3− 6 +  e−	⇌	Cr(CN)4− 6	−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	2H3PO4(aq) + 2 H+ + 2 e−	⇌	(H2PO3)2(aq) + H2O(l)	−0.933	2	[6]: 789
C	CO2− 3 + 3 H+ + 2 e−	⇌	HCO− 2 + 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) + 2H2O	−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) + 3H2O	−0.89	3	[6]: 788
Fe	Fe(OH) 2(s) + 2 e−	⇌	Fe(s) + 2 OH−	−0.89	2	[12]
Fe	Fe 2O 3(s) + 3H2O + 2 e−	⇌	2Fe(OH) 2(s) + 2 OH−	−0.86	2	[12]
H	2H2O + 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 2O 5(s) + 10 H+ + 10 e−	⇌	2Ta(s) + 5H2O	−0.75	10
Te	2Te(s) + 2 e−	⇌	Te2− 2	−0.74	2	[6]: 790
Ni	Ni(OH) 2(s) + 2 e−	⇌	Ni(s) + 2 OH−	−0.72	2	[1]
Nb	Nb2O5(s) + 10 H+ + 10 e−	⇌	2Nb(s) + 5H2O(l)	−0.7	10	[6]: 793
Ag	Ag 2S(s) + 2 e−	⇌	2Ag(s) + S2− (aq)	−0.69	2
Te	Te2− 2 + 4 H+ + 2 e−	⇌	2H2Te(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) + 2CN−	−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	2TiO 2(s) + 2 H+ + 2 e−	⇌	Ti 2O 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 3PO 2(aq) +  H+ +  e−	⇌	P(white)[note 1] + 2H2O	−0.508	1	[10]
P	H 3PO 3(aq) + 2 H+ + 2 e−	⇌	H 3PO 2(aq) + H2O	−0.499	2	[10]
Ni	NiO 2(s) + 2H2O + 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 3PO 3(aq) + 3 H+ + 3 e−	⇌	P(red)[note 1] + 3H2O	−0.454	3	[10]
Bi	Bi2O3(s) + 3H2O(l) + 6 e−	⇌	Bi(s) + 6 OH−	−0.452	6	[6]: 789
Ta	TaF2− 7 + 7 H+ + 5 e−	⇌	Ta(s) + 7HF(l)	−0.45	5	[6]: 793
In	In3+ + 2 e−	⇌	In+	−0.444	2	[6]: 788
Cu	Cu(CN)− 2 +  e−	⇌	Cu(s) + 2CN−	−0.44	1	[13]
Fe	Fe2+ + 2 e−	⇌	Fe(s)	−0.44	2	[7]
C	2CO 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]
Cr	Cr3+ + 3 e−	⇌	Cr(s)	−0.74	3	[7]
Ti	Ti3+ +  e−	⇌	Ti2+	−0.37	1	[6]: 792
Cu	Cu 2O(s) + H2O + 2 e−	⇌	2Cu(s) + 2 OH−	−0.36	2	[10]
Pb	PbSO 4(s) + 2 e−	⇌	Pb(s) + SO2− 4	−0.3588	2	[10]
Pb	PbSO 4(s) + 2 e−	⇌	Pb(Hg) + SO2− 4	−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 3PO 4(aq) + 2 H+ + 2 e−	⇌	H 3PO 3(aq) + H2O	−0.276	2	[10]
N	N2(g) + 8 H+ + 6 e−	⇌	2NH+ 4	−0.27	6	[16]
V	V3+ +  e−	⇌	V2+	−0.26	1	[7]
Ni	Ni2+ + 2 e−	⇌	Ni(s)	−0.257	2	[8]
S	2HSO− 4 + 2 H+ + 2 e−	⇌	S2O2− 6 + 2H2O(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−	⇌	N2H+ 5	−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) + 2H2O(l)	−0.15	4	[16]
Mo	MoO 2(s) + 4 H+ + 4 e−	⇌	Mo(s) + 2H2O	−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) + 2H2O	−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 2Se(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(NH 3)+ 2 +  e−	⇌	Cu(s) + 2NH 3(aq)	−0.1	1	[13]
Nb	Nb2O5(s) + 10 H+ + 4 e−	⇌	2Nb3+ + 5H2O(l)	−0.1	4	[6]: 793
W	WO 3(aq) + 6 H+ + 6 e−	⇌	W(s) + 3H2O	−0.09	6	[13]
Sn	SnO 2(s) + 2 H+ + 2 e−	⇌	α-SnO(s) + H2O	−0.088	2	[6]: 788
Fe	Fe 3O 4(s) + 8 H+ + 8 e−	⇌	3Fe(s) + 4H2O	−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−	⇌	2NH3OH+	−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	S 4O2− 6 + 2 e−	⇌	2S 2O2− 3	0.08	2
N	N 2(g) + 2H2O + 6 H+ + 6 e−	⇌	2NH 4OH(aq)	0.092	6
Hg	HgO(s) + H2O + 2 e−	⇌	Hg(l) + 2 OH−	0.0977	2
Cu	Cu(NH 3)2+ 4 +  e−	⇌	Cu(NH 3)+ 2 + 2NH 3(aq)	0.1	1	[13]
Ru	Ru(NH 3)3+ 6 +  e−	⇌	Ru(NH 3)2+ 6	0.1	1	[15]
N	N 2H 4(aq) + 4H2O + 2 e−	⇌	2NH+ 4 + 4 OH−	0.11	2	[4]
Mo	H 2MoO 4(aq) + 6 H+ + 6 e−	⇌	Mo(s) + 4H2O	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 3OH(aq)	0.13	2
S	S(s) + 2 H+ + 2 e−	⇌	H 2S(g)	0.144	2	[6]: 790
Sb	Sb2O3(s) + 6 H+ + 6 e−	⇌	2Sb(s) + 3H2O	0.15	6	[6]: 789
Sn	Sn4+ + 2 e−	⇌	Sn2+	0.151	2	[8]
S	HSO− 4 + 3 H+ + 2 e−	⇌	SO 2(aq) + 2H2O	0.158	2	[6]: 790
Cu	Cu2+ +  e−	⇌	Cu+	0.159	1	[13]
U	UO2+ 2 +  e−	⇌	UO+ 2	0.163	1	[15]
S	SO2− 4 + 4 H+ + 2 e−	⇌	SO 2(aq) + 2H2O	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	3Fe 2O 3(s) + 2 H+ + 2 e−	⇌	2Fe 3O 4(s) + H2O	0.22	2	[18]: p.100
Ag	AgCl(s) +  e−	⇌	Ag(s) + Cl−	0.22233	1	[10]
As	H 3AsO 3(aq) + 3 H+ + 3 e−	⇌	As(s) + 3H2O	0.24	3	[6]: 789
Ru	Ru3+ (aq) +  e−	⇌	Ru2+ (aq)	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−	⇌	2Hg(l) + 2Cl−	0.27	2	[16]
U	UO+ 2 + 4 H+ +  e−	⇌	U4+ + 2H2O	0.273	1	[15]
Re	Re3+ + 3 e−	⇌	Re(s)	0.300	3	[8]
At	At +  e−	⇌	At−	0.3	1	[20]
Bi	Bi3+ + 3 e−	⇌	Bi(s)	0.308	3	[10]
C	2HCNO + 2 H+ + 2 e−	⇌	(CN)2 + 2H2O	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−	⇌	2HCN	0.373	2	[8]
P	(H2PO3)2(aq) + 2 H+ + 2 e−	⇌	2H3PO3	0.38	2	[6]: 789
S	2SO2(aq) + 2 H+ + 2 e−	⇌	S2O2− 3 + H2O(l)	0.4	2	[6]: 790
O	O 2(g) + 2H2O + 4 e−	⇌	4 OH−(aq)	0.401	4	[7]
Mo	H 2MoO 4 + 6 H+ + 3 e−	⇌	Mo3+ + 4H2O	0.43	3
Ru	Ru2+ (aq) + 2 e−	⇌	Ru	0.455	2	[19]
V	VO(OH)+ + 2 H+ +  e−	⇌	VOH2+ + H2O(l)	0.481	1	[6]: 793
C	CH 3OH(aq) + 2 H+ + 2 e−	⇌	CH 4(g) + H2O	0.5	2
S	SO 2(aq) + 4 H+ + 4 e−	⇌	S(s) + 2H2O	0.5	4	[6]: 790
S	4SO 2(aq) + 4 H+ + 8 e−	⇌	S4O2− 6 + 2H2O(l)	0.51	8	[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	I− 3 + 2 e−	⇌	3I−	0.53	2	[7]
Te	TeO2(s) + 4 H+ + 4 e−	⇌	Te(s) + 2H2O(l)	0.53	4	[6]: 790
Cu	Cu2+ + Cl− +  e−	⇌	CuCl(s)	0.54	1	[16]
I	I 2(s) + 2 e−	⇌	2I−	0.54	2	[7]
Au	[AuI 4]− + 3 e−	⇌	Au(s) + 4I−	0.56	3
As	H 3AsO 4(aq) + 2 H+ + 2 e−	⇌	H 3AsO 3(aq) + H2O	0.56	2	[6]: 789
S	S2O2− 6 + 4 H+ + 2 e−	⇌	2H2SO3	0.569	2	[6]: 790
Au	[AuI 2]− +  e−	⇌	Au(s) + 2I−	0.58	1
Mn	MnO− 4 + 2H2O + 3 e−	⇌	MnO 2(s) + 4 OH−	0.595	3	[1]
S	S 2O2− 3 + 6 H+ + 4 e−	⇌	2S(s) + 3H2O	0.6	4	[6]: 790
Fe	Fc+ +  e−	⇌	Fc(s)	0.63	1	Substantial literature variation[23]
Mo	H 2MoO 4(aq) + 2 H+ + 2 e−	⇌	MoO 2(s) + 2H2O	0.65	2
N	HN3(aq) + 11 H+ + 8 e−	⇌	3NH+ 4	0.69	8	[16]
O	O 2(g) + 2 H+ + 2 e−	⇌	H 2O 2(aq)	0.695	2	[8]
Sb	Sb2O5(s) + 4 H+ + 4 e−	⇌	Sb2O3(s) + 2H2O	0.699	4	[6]: 789
C	+ 2 H+ + 2 e−	⇌		0.6992	2	[10]
V	H2V10O4− 28 + 24 H+ + 10 e−	⇌	10VO(OH)+ + 8H2O(l)	0.723	10	[6]: 793
Pt	PtCl2− 6 + 2 e−	⇌	PtCl2− 4 + 2Cl−	0.726	2	[15]
Fe	Fe 2O 3(s) + 6 H+ + 2 e−	⇌	2Fe2+ + 3H2O	0.728	2	[18]: p.100
Se	H 2SeO 3(aq) + 4 H+ + 4 e−	⇌	Se(s) + 3H2O	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	PtCl2− 4 + 2 e−	⇌	Pt(s) + 4Cl−	0.758	2	[15]
Br	BrO− + H2O(l) + 2 e−	⇌	Br− + 2 OH−	0.76	2	[6]: 791
Po	Po4+ + 4 e−	⇌	Po	0.76	4	[8]
S	(SCN)2 + 2 e−	⇌	2SCN−	0.769	2	[25][8]
Fe	Fe3+ +  e−	⇌	Fe2+	0.771	1	[8]
Hg	Hg2+ 2 + 2 e−	⇌	2Hg(l)	0.7973	2	[8]
Ag	Ag+ +  e−	⇌	Ag(s)	0.7996	1	[10]
N	2NO− 3(aq) + 4 H+ + 2 e−	⇌	N 2O 4(g) + 2H2O	0.803	2	[6]: 789
Fe	2FeO2− 4 + 5H2O + 6 e−	⇌	Fe 2O 3(s) + 10 OH−	0.81	6	[12]
Au	[AuBr 4]− + 3 e−	⇌	Au(s) + 4Br−	0.85	3
Hg	Hg2+ + 2 e−	⇌	Hg(l)	0.85	2
Ir	[IrCl 6]2− +  e−	⇌	[IrCl 6]3−	0.87	1	[6]: 153
Mn	MnO− 4 +  H+ +  e−	⇌	HMnO− 4	0.9	1
Po	Po4+ + 2 e−	⇌	Po2+	0.9	2	[8]
Hg	2Hg2+ + 2 e−	⇌	Hg2+ 2	0.91	2	[13]
Pd	Pd2+ + 2 e−	⇌	Pd(s)	0.915	2	[15]
Au	[AuCl 4]− + 3 e−	⇌	Au(s) + 4Cl−	0.93	3
N	NO− 3 + 3 H+ + 2 e−	⇌	HNO2(aq)	0.94	2	[6]: 789
Mn	MnO 2(s) + 4 H+ +  e−	⇌	Mn3+ + 2H2O	0.95	1
N	NO− 3(aq) + 4 H+ + 3 e−	⇌	NO(g) + 2H2O(l)	0.958	3	[7]
Au	[AuBr 2]− +  e−	⇌	Au(s) + 2Br−	0.96	1
Fe	Fe 3O 4(s) + 8 H+ + 2 e−	⇌	3Fe2+ + 4H2O	0.98	2	[18]: p.100
Xe	[HXeO 6]3− + 2H2O + 2 e−	⇌	[HXeO 4]− + 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]+ (aq) + 2 H+ +  e−	⇌	[VO]2+ (aq) + H2O	1	1	[27]
Te	H 6TeO 6(aq) + 2 H+ + 2 e−	⇌	TeO 2(s) + 4H2O	1.02	2	[27]
N	NO2(g) + 2 H+ + 2 e−	⇌	NO(g) + H2O(l)	1.03	2	[16]
Br	Br− 3 + 2 e−	⇌	3Br−	1.05	2	[16]
Sb	Sb2O5(s) + 2 H+ + 2 e−	⇌	Sb2O4(s) + H2O(l)	1.055	2	[6]: 789
I	ICl− 2 +  e−	⇌	2Cl− + I(s)	1.06	1	[16]
Br	Br 2(l) + 2 e−	⇌	2Br−	1.066	2	[10]
N	N2O4(g) + 2 H+ + 2 e−	⇌	2HNO2	1.07	2	[6]: 789
Br	Br 2(aq) + 2 e−	⇌	2Br−	1.0873	2	[10]
Ru	RuO 2 + 4 H+ + 2 e−	⇌	Ru2+ (aq) + 2H2O	1.120	2	[19]
Cu	Cu2+ + 2CN− +  e−	⇌	Cu(CN)− 2	1.12	1	[13]
I	IO− 3 + 5 H+ + 4 e−	⇌	HIO(aq) + 2H2O	1.13	4	[6]: 791
O	H2O2(aq) +  H+ +  e−	⇌	H2O(l) + HO•	1.14	1	[6]: 790
Au	[AuCl 2]− +  e−	⇌	Au(s) + 2Cl−	1.15	1
Se	HSeO− 4 + 3 H+ + 2 e−	⇌	H 2SeO 3(aq) + H2O	1.15	2	[6]: 790
Ag	Ag 2O(s) + 2 H+ + 2 e−	⇌	2Ag(s) + H2O	1.17	2
Cl	ClO− 3 + 2 H+ +  e−	⇌	ClO 2(g) + H2O	1.175	1	[6]: 791
Xe	[HXeO 6]3− + 5H2O + 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	2IO− 3 + 12 H+ + 10 e−	⇌	I 2(s) + 6H2O	1.2	10	[16]
Mn	MnO 2(s) + 4 H+ + 2 e−	⇌	Mn2+ + 2H2O	1.224	2	[10]
O	O 2(g) + 4 H+ + 4 e−	⇌	2H2O	1.229	4	[7]
N	N2H+ 5 + 3 H+ + 2 e−	⇌	2NH+ 4	1.28	2	[6]: 789
Cl	ClO− 4 + 2 H+ + 2 e−	⇌	ClO− 3 + H2O	1.23	2	[29]
Ru	[Ru(bipy) 3]3+ +  e−	⇌	[Ru(bipy) 3]2+	1.24	1	[1]
Xe	[HXeO 4]− + 3H2O + 6 e−	⇌	Xe(g) + 7 OH−	1.24	6	[6]: 792 [26]
N	2NO− 3 + 12 H+ + 10 e−	⇌	N2(g) + 6H2O(l)	1.25	10	[6]: 789
Tl	Tl3+ + 2 e−	⇌	Tl+	1.25	2	[6]: 788
N	2HNO2(aq) + 4 H+ + 4 e−	⇌	N2O(g) + 3H2O(l)	1.297	4	[6]: 789
Cr	Cr 2O2− 7 + 14 H+ + 6 e−	⇌	2Cr3+ + 7H2O	1.33	6	[4]: 1005
N	NH3OH+ + 2 H+ + 2 e−	⇌	NH+ 4 + H2O(l)	1.35	2	[6]: 789
Cl	Cl 2(g) + 2 e−	⇌	2Cl−	1.36	2	[7]
Ru	RuO− 4(aq) + 8 H+ + 5 e−	⇌	Ru2+ (aq) + 4H2O	1.368	5	[19]
Ru	RuO 4 + 4 H+ + 4 e−	⇌	RuO 2 + 2H2O	1.387	4	[19]
Co	CoO 2(s) + 4 H+ +  e−	⇌	Co3+ + 2H2O	1.42	1
N	2NH 3OH+ +  H+ + 2 e−	⇌	N 2H+ 5 + 2H2O	1.42	2	[4]
I	2HIO(aq) + 2 H+ + 2 e−	⇌	I 2(s) + 2H2O	1.44	2	[6]: 791
Br	BrO− 3 + 5 H+ + 4 e−	⇌	HBrO(aq) + 2H2O	1.447	4	[6]: 791
Pb	β-PbO 2(s) + 4 H+ + 2 e−	⇌	Pb2+ + 2H2O	1.46	2	[13]
Pb	α-PbO 2(s) + 4 H+ + 2 e−	⇌	Pb2+ + 2H2O	1.468	2	[13]
Br	2BrO− 3 + 12 H+ + 10 e−	⇌	Br 2(l) + 6H2O	1.48	10
At	HAtO3 + 4 H+ + 4 e−	⇌	HAtO + 2H2O	1.5	4	[20]
Mn	MnO− 4 + 8 H+ + 5 e−	⇌	Mn2+ + 4H2O	1.51	5	[16]
O	HO• 2 +  H+ +  e−	⇌	H 2O 2(aq)	1.51	1
Au	Au3+ + 3 e−	⇌	Au(s)	1.52	3
Ru	RuO2− 4(aq) + 8 H+ + 4 e−	⇌	Ru2+ (aq) + 4H2O	1.563	4	[19]
N	2NO(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	2HClO(aq) + 2 H+ + 2 e−	⇌	Cl 2(g) + 2H2O	1.63	2	[28]
I	IO− 4 + 2 H+ + 2 e−	⇌	IO− 3 + H2O	1.64	2	[29]
Ag	Ag 2O 3(s) + 6 H+ + 4 e−	⇌	2Ag+ + 3H2O	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	MnO− 4 + 4 H+ + 3 e−	⇌	MnO 2(s) + 2H2O	1.7	3	[16]
Br	BrO− 4 + 2 H+ + 2 e−	⇌	BrO− 3 + 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 2O 2(aq) + 2 H+ + 2 e−	⇌	2H2O	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	S 2O2− 8 + 2 e−	⇌	2SO2− 4	2.01	2	[10]
O	O 3(g) + 2 H+ + 2 e−	⇌	O 2(g) + H2O	2.075	2	[15]
Mn	HMnO− 4 + 3 H+ + 2 e−	⇌	MnO 2(s) + 2H2O	2.09	2
Xe	XeO 3(aq) + 6 H+ + 6 e−	⇌	Xe(g) + 3H2O	2.12	6	[6]: 792 [26]
Xe	H 4XeO 6(aq) + 8 H+ + 8 e−	⇌	Xe(g) + 6H2O	2.18	8	[6]: 792 [26]
Fe	FeO2− 4 + 8 H+ + 3 e−	⇌	Fe3+ + 4H2O	2.2	3	[30]
Xe	XeF 2(aq) + 2 H+ + 2 e−	⇌	Xe(g) + 2HF(aq)	2.32	2	[26][28]
O	HO• +  H+ +  e−	⇌	H2O(l)	2.38	1	[6]: 790
Xe	H 4XeO 6(aq) + 2 H+ + 2 e−	⇌	XeO 3(aq) + 3H2O	2.42	2	[26][6]: 792
F	F 2(g) + 2 e−	⇌	2F−	2.87	2	[6]: 153 [7][13]
Cm	Cm4+ + e–	⇌	Cm3+	3.0	1	Estimated[3]
F	F 2(g) + 2 H+ + 2 e−	⇌	2HF(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) + 2F− (aq)	3.27	2	Estimated[31]

See also

• Galvanic series lists electrode potentials in saltwater
• Standard apparent reduction potentials in biochemistry at pH 7
• Reactivity series#Comparison with standard electrode potentials

Notes

1. 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.