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32:
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retained in the electrolyte, and old electrolyte may be exchanged for fresh, in a manner analogous to an oil change in a car. More space is required between electrodes to enable this flow, and this translates into an increase in cell resistance, decreasing power output compared to immobilized electrolyte designs. A further challenge for the technology is how severe the problem of permanent blocking of the cathode is by K
129:
670:
Carbonate formation depletes hydroxide ions from the electrolyte, which reduces electrolyte conductivity and consequently cell performance. As well as these bulk effects, the effect on water management due to a change in vapor pressure and/or a change in electrolyte volume can be detrimental as well.
438:
and would incorporate a 'scrubber' into the design to clean out as much of the carbon dioxide as is possible. Because the generation and storage requirements of oxygen make pure-oxygen AFCs expensive, there are few companies engaged in active development of the technology. There is, however, some
449:
When carbon dioxide reacts with the electrolyte carbonates are formed. The carbonates could precipitate on the pores of electrodes that eventually block them. It has been found that AFCs operating at higher temperature do not show a reduction in performance, whereas at around room temperature, a
683:
Flowing electrolyte designs use a more open matrix that allows the electrolyte to flow either between the electrodes (parallel to the electrodes) or through the electrodes in a transverse direction (the ASK-type or EloFlux fuel cell). In parallel-flow electrolyte designs, the water produced is
679:
Because of this poisoning effect, two main variants of AFCs exist: static electrolyte and flowing electrolyte. Static, or immobilized, electrolyte cells of the type used in the Apollo space craft and the Space
Shuttle typically use an asbestos separator saturated in potassium hydroxide. Water
698:
The electrodes consist of a double layer structure: an active electrocatalyst layer and a hydrophobic layer. The active layer consists of an organic mixture which is ground and then rolled at room temperature to form a crosslinked self-supporting sheet. The hydrophobic structure prevents the
565:
447:, which is not reversible, and reduction in the ionic conductivity of the electrolyte, which may be reversible by returning the KOH to its original concentration. An alternate method involves simply replacing the KOH which returns the cell back to its original output.
667:
398:
299:
797:
instead of a liquid electrolyte. This resolves the problem of poisoning and allows the development of alkaline fuel cells capable of running on safer hydrogen-rich carriers such as liquid urea solutions or metal amine complexes.
680:
production is controlled by evaporation from the anode, which produces pure water that may be reclaimed for other uses. These fuel cells typically use platinum catalysts to achieve maximum volumetric and specific efficiencies.
777:
AFCs are the cheapest of fuel cells to manufacture. The catalyst required for the electrodes can be any of a number of different chemicals that are inexpensive compared to those required for other types of fuel cells.
699:
electrolyte from leaking into the reactant gas flow channels and ensures diffusion of the gases to the reaction site. The two layers are then pressed onto a conducting metal mesh, and sintering completes the process.
692:; some published reports have indicated thousands of hours of operation on air. These designs have used both platinum and non-noble metal catalysts, resulting in increased efficiencies and increased cost.
174:
technologies. Alkaline fuel cells consume hydrogen and pure oxygen, to produce potable water, heat, and electricity. They are among the most efficient fuel cells, having the potential to reach 70%.
471:
568:
On the other hand, the charge-carrying hydroxide ions in the electrolyte can react with carbon dioxide from organic fuel oxidation (i.e. methanol, formic acid) or air to form carbonate species.
573:
406:
ions. The net reaction consumes one oxygen molecule and two hydrogen molecules in the production of two water molecules. Electricity and heat are formed as by-products of this reaction.
781:
The commercial prospects for AFCs lie largely with the recently developed bi-polar plate version of this technology, considerably superior in performance to earlier mono-plate versions.
695:
The EloFlux design, with its transverse flow of electrolyte, has the advantage of low-cost construction and replaceable electrolyte but so far has only been demonstrated using oxygen.
466:
that blocks the electrode pores. Also, these precipitants gradually decrease the hydrophobicity of the electrode backing layer leading to structural degradation and electrode flooding.
312:
213:
439:
debate in the research community over whether the poisoning is permanent or reversible. The main mechanisms of poisoning are blocking of the pores in the cathode with K
769:
An alkaline medium also accelerates oxidation of fuels like methanol, making them more attractive. This results in less pollution compared to acidic fuel cells.
730:. Because of the alkaline chemistry, oxygen reduction reaction (ORR) kinetics at the cathode are much more facile than in acidic cells, allowing use of non-
718:
Alkaline fuel cells operate between ambient temperature and 90 °C with an electrical efficiency higher than fuel cells with acidic electrolyte, such as
450:
significant drop in performance has been shown. The carbonate poisoning at ambient temperature is thought to be a result of the low solubility of K
96:
560:{\displaystyle \mathrm {CO} _{2}+\mathrm {2KOH} \longrightarrow \mathrm {K} _{2}\mathrm {CO} _{3}+\mathrm {H} _{2}\mathrm {O} }
68:
868:
964:
75:
49:
1002:
719:
662:{\displaystyle \mathrm {2OH} ^{-}+\mathrm {CO} _{2}\longrightarrow \mathrm {CO} _{3}^{2-}+\mathrm {H} _{2}\mathrm {O} }
115:
82:
393:{\displaystyle \mathrm {O} _{2}+\mathrm {2H} _{2}\mathrm {O} +\mathrm {4e} ^{-}\longrightarrow \mathrm {4OH} ^{-}}
294:{\displaystyle \mathrm {H} _{2}+\mathrm {2OH} ^{-}\longrightarrow \mathrm {2H} _{2}\mathrm {O} +\mathrm {2e} ^{-}}
1145:
1100:
64:
53:
1140:
1023:
707:
303:
producing water and releasing electrons. The electrons flow through an external circuit and return to the
1193:
1110:
1053:
828:
414:
The two electrodes are separated by a porous matrix saturated with an aqueous alkaline solution, such as
1130:
992:
1120:
1038:
997:
727:
750:, or carbon-based nanomaterial at the anode (where fuel is oxidized); and cheaper catalysts such as
1125:
1033:
957:
1115:
1048:
1028:
823:
794:
703:
42:
89:
1135:
1074:
434:). Because of this, alkaline fuel cells typically operate on pure oxygen, or at least purified
1043:
1007:
838:
723:
185:
1058:
167:
8:
1214:
1079:
950:
423:
415:
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Another recent development is the solid-state alkaline fuel cell, utilizing a solid
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900:
888:
759:
197:
181:
1208:
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815:
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20:
1105:
785:
422:) so the fuel cell can become "poisoned" through the conversion of KOH to
731:
973:
833:
747:
403:
171:
31:
1157:
932:
201:
861:
Handbook of fuel cells: fundamentals, technology, and applications
418:(KOH). Aqueous alkaline solutions do not reject carbon dioxide (CO
809:
304:
937:
751:
743:
739:
128:
942:
205:
927:
735:
177:
458:
around room temperature, which leads to precipitation of K
702:
Further variations on the alkaline fuel cell include the
435:
180:
has used alkaline fuel cells since the mid-1960s, in the
863:. Chichester, England ; Hoboken, N.J: Wiley. 2003.
763:
576:
474:
315:
216:
805:
713:
56:. Unsourced material may be challenged and removed.
887:Ferriday, T.B.; Middleton, Peter Hugh (May 2021).
855:
853:
661:
559:
392:
293:
208:, hydrogen is oxidized according to the reaction:
886:
1206:
790:, used an AFC system with 5 kW net output.
850:
882:
880:
958:
877:
965:
951:
889:"Alkaline fuel cell technology - A review"
904:
116:Learn how and when to remove this message
893:International Journal of Hydrogen Energy
127:
772:
196:The fuel cell produces power through a
1207:
784:The world's first fuel-cell ship, the
946:
54:adding citations to reliable sources
25:
720:proton-exchange membrane fuel cells
307:, reducing oxygen in the reaction:
13:
1003:Proton-exchange membrane fuel cell
655:
644:
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14:
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916:
714:Advantages over acidic fuel cells
191:
132:Diagram of an Alkaline Fuel Cell:
808:
674:
30:
1146:Unitized regenerative fuel cell
754:at the cathode, due to the low
170:, is one of the most developed
41:needs additional citations for
972:
906:10.1016/j.ijhydene.2021.02.203
613:
507:
409:
369:
250:
1:
1141:Solid oxide electrolyzer cell
844:
1024:Direct borohydride fuel cell
708:direct borohydride fuel cell
184:-series missions and on the
166:after its British inventor,
7:
1111:Membrane electrode assembly
1054:Reformed methanol fuel cell
829:Glossary of fuel cell terms
801:
10:
1231:
1131:Protonic ceramic fuel cell
1101:Electro-galvanic fuel cell
993:Molten carbonate fuel cell
728:phosphoric acid fuel cells
18:
1189:
1156:
1121:Photoelectrochemical cell
1088:
1067:
1039:Direct methanol fuel cell
1016:
998:Phosphoric acid fuel cell
980:
1126:Proton-exchange membrane
1034:Direct-ethanol fuel cell
19:Not to be confused with
1116:Membraneless Fuel Cells
1049:Metal hydride fuel cell
1029:Direct carbon fuel cell
824:Gas diffusion electrode
795:anion-exchange membrane
704:metal hydride fuel cell
1136:Regenerative fuel cell
1075:Enzymatic biofuel cell
724:solid oxide fuel cells
663:
561:
394:
295:
151:
1044:Formic acid fuel cell
1008:Solid oxide fuel cell
839:Hydrogen technologies
664:
562:
395:
296:
162:), also known as the
131:
773:Commercial prospects
574:
472:
313:
214:
204:and oxygen. At the
168:Francis Thomas Bacon
65:"Alkaline fuel cell"
50:improve this article
1080:Microbial fuel cell
899:(35): 18489–18510.
638:
424:potassium carbonate
416:potassium hydroxide
988:Alkaline fuel cell
762:reactions at high
659:
616:
557:
390:
291:
156:alkaline fuel cell
152:
1202:
1201:
933:Independent Power
870:978-0-471-49926-8
150:9. Hydroxide Ions
136:2. Electron flow
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125:
118:
100:
16:Type of fuel cell
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1059:Zinc–air battery
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164:Bacon fuel cell
149:
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144:6. Electrolyte
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1005:
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981:By electrolyte
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938:Gencell Energy
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917:External links
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198:redox reaction
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192:Half Reactions
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1068:Biofuel cells
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816:Energy portal
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675:Basic designs
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67: –
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61:Find sources:
55:
51:
45:
44:
39:This article
37:
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28:
27:
22:
21:Alkaline cell
1106:Flow battery
987:
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732:noble metals
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134:1. Hydrogen
112:
106:January 2022
103:
93:
86:
79:
72:
60:
48:Please help
43:verification
40:
1096:Blue energy
410:Electrolyte
142:5. Cathode
1215:Fuel cells
974:Fuel cells
928:AFC Energy
922:Developers
845:References
734:, such as
402:producing
140:4. Oxygen
76:newspapers
834:Hydrazine
748:manganese
722:(PEMFC),
635:−
614:⟶
591:−
508:⟶
404:hydroxide
386:−
370:⟶
365:−
287:−
251:⟶
246:−
172:fuel cell
148:8. Water
146:7. Anode
1209:Category
1194:Glossary
1158:Hydrogen
802:See also
706:and the
202:hydrogen
200:between
138:3. Load
1181:Vehicle
1176:Storage
1171:Station
1166:Economy
1017:By fuel
305:cathode
90:scholar
1089:Others
867:
752:silver
744:nickel
740:cobalt
726:, and
182:Apollo
92:
85:
78:
71:
63:
787:Hydra
206:anode
97:JSTOR
83:books
865:ISBN
736:iron
178:NASA
154:The
69:news
901:doi
436:air
160:AFC
52:by
1211::
897:46
895:.
891:.
879:^
852:^
766:.
764:pH
746:,
742:,
738:,
710:.
688:CO
462:CO
454:CO
443:CO
430:CO
426:(K
188:.
966:e
959:t
952:v
909:.
903::
873:.
690:3
686:2
656:O
650:2
645:H
640:+
632:2
627:3
622:O
619:C
609:2
604:O
601:C
596:+
586:H
583:O
580:2
554:O
548:2
543:H
538:+
533:3
528:O
525:C
518:2
513:K
504:H
501:O
498:K
495:2
491:+
486:2
481:O
478:C
464:3
460:2
456:3
452:2
445:3
441:2
432:3
428:2
420:2
381:H
378:O
375:4
360:e
357:4
352:+
348:O
342:2
337:H
334:2
329:+
324:2
319:O
282:e
279:2
274:+
270:O
264:2
259:H
256:2
241:H
238:O
235:2
230:+
225:2
220:H
158:(
119:)
113:(
108:)
104:(
94:·
87:·
80:·
73:·
46:.
23:.
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