198:
294:
In 1953 in
Stockholm IUPAC recognized that either of the conventions is permissible; however, it unanimously recommended that only the magnitude expressed according to the convention (2) be called "the electrode potential". To avoid possible ambiguities, the electrode potential thus defined can also
506:
This follows from the IUPAC definition of the electric potential difference of a galvanic cell, according to which the electric potential difference of a cell is the difference of the potentials of the electrodes on the right and the left of the galvanic cell. When
501:
435:
138:
356:. Proponents of the convention (2) argue that all reported electrode potentials should be consistent with the electrostatic sign of the relative potential difference.
147:
at the working electrode ("reversible potential"), or a potential with a non-zero net reaction on the working electrode but zero net current ("corrosion potential", "
215:
81:
In an electrochemical cell, the cathode and the anode have certain electrode potentials independently and the difference between them is the cell potential:
447:
384:
658:
602:
598:
373:
631:
C.A. Hamel, "The
Encyclopedia of Electrochemistry", Reinhold Publishing Corporation, New York-Chapman & Hall Ltd., London, 1964, p. 429–431.
87:
299:. In both conventions, the standard hydrogen electrode is defined to have a potential of 0 V. Both conventions also agree on the sign of
185:
involves this reference electrode with hydrogen ion in an ideal solution having is "zero potential at all temperatures" equivalently to
170:
The value of the electrode potential under non-equilibrium depends on the nature and composition of the contacting phases, and on the
640:
P. van
Rysselberghe, "Bericht der Kommission für electrochemische Nomenklatur und Definitionen", Z. Electrochem., 58 (1954), 530–535.
570:
50:
The electrode potential has its origin in the potential difference developed at the interface between the electrode and the
701:
352:
switches sign when a reaction is written in reverse, so too, proponents of the convention (1) argue, should the sign of
235:
in the electrolyte, e.g., by positioning the reference electrode near the surface of the working electrode (e.g., see
378:
Potential of a cell assembled of two electrodes can be determined from the two individual electrode potentials using
186:
74:
due to the transfer of charged species across the interface, specific adsorption of ions at the interface, and
306:
The main difference between the two conventions is that upon reversing the direction of a half-cell reaction
649:
Anson, Fred C. "Common sources of confusion; Electrode Sign
Conventions," J. Chem. Educ., 1959, 36, p. 394.
565:
534:
160:
369:
47:. It may also be defined as the potential difference between the charged metallic rods and salt solution.
244:
182:
40:
175:
696:
144:
272:
171:
314:
also switches, whereas in the convention (2) it does not. The logic behind switching the sign of
575:
345:. It is assumed that the half-reaction is balanced by the appropriate SHE half-reaction. Since
240:
148:
517:
is positive, then positive electrical charge flows through the cell from the left electrode (
67:
279:
268:
365:
8:
251:
connected to the working electrode and the negative terminal to the reference electrode.
221:
39:
and another electrode to be characterized. By convention, the reference electrode is the
205:
The measurement is generally conducted using a three-electrode setup (see the drawing):
539:
152:
544:
374:
Electrolytic cell § Anode and cathode definitions depend on charge and discharge
319:
209:
668:
612:
675:
663:
616:
607:
496:{\displaystyle \Delta V_{\text{cell}}=E_{\text{red,cathode}}+E_{\text{oxy,anode}}.}
342:
236:
20:
430:{\displaystyle \Delta V_{\text{cell}}=E_{\text{red,cathode}}-E_{\text{red,anode}}}
228:
In case of non-zero net current on the electrode, it is essential to minimize the
181:
An operational assumption for determinations of the electrode potentials with the
580:
549:
283:
163:
for a given electroactive species by extrapolation of the measured values to the
151:"), or a potential with a non-zero net current on the working electrode (like in
259:
Historically, two conventions for sign for the electrode potential have formed:
264:
164:
247:. The potential measurements are performed with the positive terminal of the
690:
667:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "
611:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "
554:
359:
75:
32:
679:
620:
248:
229:
156:
71:
54:. It is common, for instance, to speak of the electrode potential of the
51:
197:
287:
36:
133:{\displaystyle E_{\text{cell}}=E_{\text{cathode}}-E_{\text{anode}}.}
559:
522:
232:
78:/orientation of polar molecules, including those of the solvent.
28:
518:
44:
303:
for a half-cell reaction when it is written as a reduction.
201:
Three-electrode setup for measurement of electrode potential
159:). Reversible potentials can be sometimes converted to the
360:
Potential difference of a cell assembled of two electrodes
318:
is to maintain the correct sign relationship with the
450:
387:
90:
16:
Electromotive force of a cell built of two electrodes
189:
of hydrogen ion is also "zero at all temperatures".
495:
429:
132:
43:(SHE). It is defined to have a potential of zero
688:
224:(standard hydrogen electrode or an equivalent).
310:, according to the convention (1) the sign of
143:The electrode potential may be either that at
61:
370:Electrochemical cell § Cell potential
337:is the number of electrons involved and
290:" (sometimes referred to as "European").
275:" (sometimes referred to as "American"),
196:
689:
571:Table of standard electrode potentials
297:Gibbs–Stockholm electrode potential
254:
66:Electrode potential appears at the
13:
669:electric potential difference, ΔV
664:Compendium of Chemical Terminology
625:
608:Compendium of Chemical Terminology
451:
388:
14:
713:
366:Galvanic cell § Cell voltage
35:built from a standard reference
172:kinetics of electrode reactions
652:
643:
634:
592:
192:
187:standard enthalpy of formation
1:
586:
566:Standard electrode potential
535:Absolute electrode potential
161:standard electrode potential
7:
528:
183:standard hydrogen electrode
41:standard hydrogen electrode
10:
718:
702:Electrochemical potentials
521:) to the right electrode (
363:
70:between an electrode and
62:Origin and interpretation
680:10.1351/goldbook.E01934
621:10.1351/goldbook.E01956
613:electrode potential, E
576:Thermodynamic activity
497:
431:
241:supporting electrolyte
202:
176:Butler–Volmer equation
174:at the interface (see
134:
498:
437:however , it depends.
432:
243:of sufficiently high
200:
135:
560:Potential difference
448:
385:
88:
222:reference electrode
76:specific adsorption
25:electrode potential
671:of a galvanic cell
540:Electric potential
493:
441:or, equivalently,
427:
295:be referred to as
203:
153:galvanic corrosion
130:
545:Galvani potential
487:
474:
461:
424:
411:
398:
322:change, given by
320:Gibbs free energy
239:), or by using a
216:counter electrode
210:working electrode
124:
111:
98:
709:
697:Electrochemistry
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343:Faraday constant
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255:Sign conventions
237:Luggin capillary
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21:electrochemistry
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581:Volta potential
550:Nernst equation
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149:mixed potential
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17:
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5:
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165:standard state
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129:
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60:
58:redox couple.
15:
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3:
2:
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579:
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555:Overpotential
553:
551:
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520:
512:
490:
481:
477:
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92:
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69:
59:
53:
48:
46:
42:
38:
34:
33:galvanic cell
30:
26:
22:
670:
662:
654:
645:
636:
627:
606:
594:
510:
505:
440:
377:
348:
329:
325:
307:
305:
296:
293:
278:convention "
263:convention "
258:
249:electrometer
245:conductivity
227:
204:
180:
169:
142:
80:
65:
49:
24:
18:
473:red,cathode
410:red,cathode
193:Measurement
157:voltammetry
145:equilibrium
72:electrolyte
52:electrolyte
691:Categories
587:References
364:See also:
308:as written
562:(voltage)
486:oxy,anode
452:Δ
423:red,anode
415:−
389:Δ
288:Stockholm
115:−
68:interface
37:electrode
529:See also
523:cathode
341:is the
284:Ostwald
273:Latimer
233:IR-drop
110:cathode
29:voltage
27:is the
372:, and
333:where
265:Nernst
659:IUPAC
603:IUPAC
599:IUPAC
519:anode
280:Gibbs
269:Lewis
230:ohmic
123:anode
45:volts
31:of a
514:cell
460:cell
397:cell
97:cell
676:doi
674:".
617:doi
615:".
525:).
330:nFE
328:= –
178:).
155:or
56:M/M
19:In
693::
661:,
605:,
601:,
368:,
167:.
23:,
678::
619::
511:V
509:Δ
491:.
482:E
478:+
469:E
465:=
456:V
419:E
406:E
402:=
393:V
354:E
349:G
347:Δ
339:F
335:n
326:G
324:Δ
316:E
312:E
301:E
286:–
282:–
271:–
267:–
218:,
212:,
128:.
119:E
106:E
102:=
93:E
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