Standard electrode potential (data page)

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

• Temperature 298.15 K (25.00 °C; 77.00 °F);
• Effective concentration 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).

The Nernst equation adjusts for general concentrations, pressures, or temperatures.

Simultaneous half-reactions do not in general add voltages, but instead add Gibbs free energy change: the product of the voltage and the number of electrons transferred, typically the Faraday constant. For example, from Fe²⁺ + 2 e⁻ ⇌ Fe(s) (–0.44 V), the energy to create one neutral atom of Fe(s) from one Fe²⁺ ion and two electrons is 2 × 0.44 eV = 0.88 eV, or 84 895 J/(mol  e⁻). That value is also the standard formation energy for an Fe²⁺ ion, since  e⁻ and Fe(s) both have zero formation energy.

Data from different sources may cause table inconsistencies. For example:

$${\displaystyle {\begin{alignedat}{4}&{\ce {Cu+ + e-}}&{}\rightleftharpoons {}&{\ce {Cu}}(s)&\quad \quad E_{1}=+0.520{\text{ V}}\\&{\ce {Cu^2+ + 2e-}}&{}\rightleftharpoons {}&{\ce {Cu}}&\quad \quad E_{2}=+0.337{\text{ V}}\\&{\ce {Cu^2+ + e-}}&{}\rightleftharpoons {}&{\ce {Cu+}}&\quad \quad E_{3}=+0.159{\text{ V}}\end{alignedat}}}$$

$${\displaystyle E_{3}={\frac {2\cdot E_{2}-1\cdot E_{1}}{1}}=0.154{\text{ V,}}}$$

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° / V	Electrons	Ref.
	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	AlF<span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">3−</sup><br/><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">6</sub></span> + 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	[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	1.38	6	[6]: 793
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]