WO2003095705A1 - Electrode divisee s'utilisant dans des cellules electrolytiques - Google Patents

Electrode divisee s'utilisant dans des cellules electrolytiques Download PDF

Info

Publication number
WO2003095705A1
WO2003095705A1 PCT/CA2002/000697 CA0200697W WO03095705A1 WO 2003095705 A1 WO2003095705 A1 WO 2003095705A1 CA 0200697 W CA0200697 W CA 0200697W WO 03095705 A1 WO03095705 A1 WO 03095705A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrode
screen
evolving
electrolyte
gas
Prior art date
Application number
PCT/CA2002/000697
Other languages
English (en)
Inventor
Donald W. Kirk
John W. Graydon
Original Assignee
Kirk Donald W
Graydon John W
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kirk Donald W, Graydon John W filed Critical Kirk Donald W
Priority to AU2002302231A priority Critical patent/AU2002302231A1/en
Priority to PCT/CA2002/000697 priority patent/WO2003095705A1/fr
Publication of WO2003095705A1 publication Critical patent/WO2003095705A1/fr

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous

Definitions

  • This invention relates to bifurcated metal electrodes, particularly formed of nickel of use in electrolytic cells, particularly water electrolyser cells for the production of hydrogen.
  • bipolar cells In the field of electrolysis, there are two types of electrochemical cell stacks, namely, monopolar cell stacks and bipolar cell stacks.
  • Bipolar cells have electrodes that operate with one side of the electrode as an anode while the other side operates as a cathode.
  • Monopolar electrodes operate with one side or both sides as either an anode or as a cathode, but not both.
  • the difference in these electrode types means that bipolar cells are connected in series with only 2 electrical connections one at each end of the cell stack while monopolar cells have multiple parallel type electrical connections.
  • Stack construction is simpler and usually less expensive for bipolar cells than for monopolar cells.
  • electrolyte channel(s) must be present for each electrode.
  • a membrane, diaphragm or separator is placed in the electrolyte channel which separates the cell into anolyte and catholyte compartments.
  • the membrane allows only selective ions to pass between compartments, the diaphragm allows electrolyte to pass but prevents gaseous products from passing between compartments, while a separator can be used to isolate cell compartments in some monopolar designs.
  • the electrolyte channel is necessary for the operation of the cell since the electrolyte has the ions required to complete the electrical circuit.
  • Electrodes are particularly useful for plating of very dilute species from aqueous waste waters.
  • porous electrodes are not desirable because they trap the gases produced and, hence, increase the resistance of the gas-filled electrolyte.
  • U.S. 5,480,515 teaches the use of a shaped electrode to move electrolyte to the electrode surface under the influence of gas release by means of channels.
  • the electrode design does not reduce the electrolyte resistance.
  • U.S. 4,424,106 teaches a shaped electrode for anodes and cathodes in a filter press cell stack for improvement of electrolyte and gas flow within the cell. Mixing and fluid flow are affected by the shaped electrodes but there is no reduction in cell resistance with this design.
  • U.S. 4,469,580 teaches an electrode design which increases surface area and is self-supporting.
  • the increase in surface area is achieved by having a ribbon-like screen project into the flow channel.
  • the screen must be used in a monopolar cell and must have flow on both sides of the electrode.
  • the electrode shape is not suitable for narrow gap cell designs because of the physical width of the electrode and the need for electrolyte flow on both sides of the electrode. Any advantage in electrolyte resistance reduction due to projection of the screen ribbon structure will be offset by gas hold-up due to the same.
  • the prior art does not teach how to, both, reduce electrolyte resistance and to keep an open electrolyte channel for escape of gaseous products. There is, therefore, a need for an improved electrode which addresses both of the aforesaid and other issues.
  • the invention provides an electrode of use in an electrolytic cell comprising: an electrically conductive first metal sheet having an electrochemically active gas-evolving planar surface; an electrically conductive second metal electrochemically active gas-evolving screen intimately adjacent and parallel to said planar surface to define an electrolyte and gas-evolving chamber between said sheet and said screen having a narrow width.
  • screen includes, for example, mesh, grid and the like.
  • sheet includes, for example, plate, foil, or other members having a planar surface.
  • the bifurcated electrode reduces the electrolyte resistance, but still maintains an electrolyte flow channel for electrolyte movement and escape of reactant products.
  • the bifurcated electrode is particularly suited to electrolysis which produces gases, since the presence of non-conductive gas bubbles in a narrow electrolyte flow channel increases cell resistance substantially for a conventional electrode.
  • the bifurcated electrode has two, in effect, distinct structures wherein one part is a conventional or primary plate electrode and the second part is a metallic screen or perforated plate responsible for the reduction of cell resistance.
  • the metallic screen is electrically connected to the primary plate, preferably, near the edge of the electrolyte-exposed active plate area and parallel to the flow channel and extends across the flow channel from the plate to a membrane/separator, then along the surface of the membrane/separator and returns to the electrode plate essentially covering the boundary of the flow channel wall, but not interfering with the flow channel.
  • the current is conducted to the electrolyte adjacent the membrane/separator and, thus, reduces the resistance path of the electrolyte.
  • a similar arrangement can be used in the other electrode compartment to reduce the total cell resistance.
  • the bifurcated electrode thus, increases the electrode surface area and provides an electrode which is placed very closely to the membrane/separator without blocking the electrolyte flow or creating a flow channel which is most often too small to permit product from being efficiently removed.
  • the extension to the primary electrode must, of course, be of a material which is conductive and screen-like. While a conductive sponge placed in the electrolyte flow channel would provide reduced cell resistance, it would trap gaseous products leading to displacement of the electrolyte and reduction or termination of the electrochemical reaction.
  • a primary benefit of the bifurcated electrode of the invention is that the flow channel is left open while the electrolyte resistance path is minimized.
  • the term "screen" as used herein does not include sponge-like materials having pores.
  • the bifurcated electrodes also provide for improved efficiency for the following two main reasons.
  • the electrode provides increased electrode surface area which results in a decrease in the true current density at the same nominal current density. Decreased current density decreases the activation overvoltage. For example, a 20 mesh screen with 0.38 mm diameter wire, the usable surface area is increased by 1.5 cm 2 /cm 2 . Based on the IR corrected polarization curve of a typical electrolysis cell, this decrease in the true current density decreases cell voltage by 90 mV at 95°C.
  • the decreased effective distance between electrodes results in a proportionate reduction in the contribution of the electrolyte resistance total cell resistance.
  • Decreased electrolyte resistance decreases the resistive voltage drop. For example, assuming an effective distance reduction of 50%, the resistance decreases by 0.228 ohm.cm 2 at 95°C, which decreases the cell voltage by 114 mV at a current density of 500 mA/cm 2 .
  • the bifurcated electrode In both monopolar and bipolar cells, the bifurcated electrode has more surface area available than the simple plate electrode and hence, can operate at a lower current density with less corresponding energy loss.
  • the surface area can be increased by surface roughening or by application of electrode coatings.
  • the additional electrode area provided by the bifurcated electrode obviates the need for these measures or may provide additional electrode surface for roughening and coating.
  • the additional surface area provided by the bifurcated electrode without a coating provides an unexpected advantage for electrolytic processes that are intermittent in operation.
  • High surface area coatings and catalyzed coatings often degrade when the cell potentials are allowed to be turned off. This scenario would be common with power from alternate energy sources, such as solar or wind or where the production is modulated to follow electrical grid power costs.
  • the high surface area provided by the bifurcated electrode allows the electrodes to be operated without a highly activated surface and, thus, the electrodes are exceptionally rugged and do not suffer from surface coating degradation.
  • the bifurcated electrode may also provide support for the membrane/separator, if the screen is set touching the membrane/separator on both sides.
  • the screen material may be formed of the same material as the electrode plate to minimize galvanic corrosion effects, or be different from the electrode plate material to encourage catalysis of a desired reaction.
  • the current carrying capacity of the screen material is not as critical as for the plate electrode since the screen electrode is, most preferably, inside the cell and is wetted and cooled by the electrolyte.
  • a variety of materials may be considered for the screen which are not suitable for the plate electrode.
  • Cell construction with a bifurcated electrode is not more complicated than the conventional cell construction.
  • the only added step is that the screen must be suitably shaped and electrically contacted with the plate electrode.
  • the screen is spot welded to the plate, though a simple pressure contact could also be effective if the screen was partially under a gasket such that the tightening of a cell stack provided sufficient pressure for the contact. It is preferable that the screen is stamped to form the shape of the flow channel before the attachment to the plate takes place.
  • the invention provides an electrode as hereinabove defined comprising a further one or more screens adjacent the first screen and/or other screens in parallel relationship to provide similar electrolyte and gas-evolving chambers having similar inter-screen widths.
  • the invention further provides an electrode hereinbefore defined further comprising a plurality of second electrically conductive second metal electrochemically active gas-evolving screens parallel to said first screen, spaced one screen from another to define an inter-screen electrolyte and gas-evolving chamber between said screens having a narrow width.
  • the electrode sheet and the screen(s) may be rigidly held spaced apart, one from another, for example, by suitable spacers located at the screen edges in the cell walls.
  • the electrodes as hereinbefore defined are of particular use in electrolytic cells or electrolysers for the production of hydrogen and oxygen in aqueous potassium hydroxide electrolyte.
  • the invention provides an electrolytic cell comprising an electrode as hereinbefore defined, a separator frame having peripheral portions defining a central aperture constituting an electrolyte flow channel; and wherein said gas-evolving screen defining said electrolyte and gas-evolving chamber and said second gas-evolving screens defining said inter-screen chambers are received within said aperture.
  • the invention provides an electrode having a recognizable three-dimensional structure which gives minimal flow channel obstruction and relatively large surface area. Minimal resistance is obtained because of the relatively narrow spacing of the electrode grid to the separator.
  • the plate can provide high current density capacity with ease of external connections to a bus bar. Surface activation of the electrode is possible, if desired.
  • Fig. 1 is a diagrammatic, perspective view of a bifurcated electrode according to the invention
  • Fig. 2 is a diagrammatic horizontal cross-sectional view on the line A-A 1 of Fig. 1 of the electrode in a separator frame adjacent a separator membrane;
  • Fig. 3 is a diagrammatic perspective view of a parallel plate flow-through cell according to the invention.
  • Fig. 4 is a diagrammatic horizontal cross-sectional view of an alternative embodiment of a bifurcated electrode in a separator frame having two screens according to the invention
  • Fig. 5 is a diagrammatic side sectional ⁇ view of a parallel plate flow-through cell according to the invention; and wherein the same numerals denote like parts.
  • this shows generally as 10, a nickel anode electrode consisting of a nickel foil 12 having planar surfaces of dimensions 229 mm x 150 mm x 0.074 mm, which serves both as a current conductor into the gas evolving area 14 and as a gas evolving area substrate per se.
  • a nickel screen 20 of 20 mesh, 0.38 mm diameter wire Overlaying and parallel to a face 16 of foil 12 adjacent at a narrow distance therefrom and remote from the periphery 18 of foil 12 is a nickel screen 20 of 20 mesh, 0.38 mm diameter wire.
  • screen 20 is spot-welded to foil 12 at the pair of screen edges 22 to form weld spots 24.
  • Alternative electrical conductor connections may be used.
  • Screen 20 is so shaped as to be raised at a distance of about 2.5 mm from face 14 for the maximum and very significant part of screen 20.
  • Welds 24 form an electrical connection and also maintain the aforesaid slight arch in screen 20 to be distant from the foil to thus form bifurcated electrode 10.
  • Screen 20 leaves a peripheral area 26 adjacent the full periphery of foil 12.
  • the foil and screen essentially define therebetween an electrolyte and gas-evolving chamber 28.
  • Screen 20 has short, gradually upstanding portions 30 of sufficient height, 2.4 mm in the embodiment shown, to provide the narrow displacement 28.
  • Fig 3 and Fig 5 show, in exaggeration, a wide gap flow-through cell having bifurcated electrode 10 within anode chamber 28 by means of conductive standoff brackets 35.
  • Thick plate anode 37 , cathode 36 and separator membrane 32 provide space for anolyte flow 39 and catholyte flow 38.
  • Screen 20 is parallel to and adjacent to separator membrane 32 and in electrical connection to cathode 36 by means of conductive electrical conductive standoffs 35, which have been spot welded at each end to provide connection to screen 20 and cathode plate 36.
  • Standoffs 35 provide the significant benefit of allowing current to be directed to screen 20 near membrane 32 without having to pass through the electrolyte and suffer resistive losses.
  • Fig 4 shows the embodiment of Fig 2 having an additional screen 20 1 adjacent in parallel relationship to screen 20 at a small distance of about 1.2 mm apart to define a second channel 28 ' therebetween.
  • bifurcated electrode 10 When assembled in the cell stack, bifurcated electrode 10 fits into one of the compartments of the separator frame so that the screen lies adjacent to the surface of the separator and the foil forms one of the walls of the compartment.
  • the axis of the arch may be either parallel or perpendicular to the direction of flow of the electrolyte.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)

Abstract

L'invention concerne une électrode s'utilisant dans des cellules électrolytiques, en particulier dans des cellules d'électrolyseur pour la production d'hydrogène, et qui comprend une feuille (12) d'un premier métal présentant une surface plane et émettant un gaz électrochimiquement actif ; une grille (20) faite d'un deuxième métal électriquement conductrice et émettant un gaz électrochimiquement actif, étroitement adjacente et parallèle à la surface plane, qui définit entre la feuille et la grille une chambre d'électrolyte et d'émission de gaz de largeur étroite. Cette électrode est améliorée du point de vue sa tension et de son rendement, de sa stabilité à long terme, et en ce qu'elle permet une dépolarisation périodique.
PCT/CA2002/000697 2002-05-13 2002-05-13 Electrode divisee s'utilisant dans des cellules electrolytiques WO2003095705A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2002302231A AU2002302231A1 (en) 2002-05-13 2002-05-13 Bifurcated electrode of use in electrolytic cells
PCT/CA2002/000697 WO2003095705A1 (fr) 2002-05-13 2002-05-13 Electrode divisee s'utilisant dans des cellules electrolytiques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CA2002/000697 WO2003095705A1 (fr) 2002-05-13 2002-05-13 Electrode divisee s'utilisant dans des cellules electrolytiques

Publications (1)

Publication Number Publication Date
WO2003095705A1 true WO2003095705A1 (fr) 2003-11-20

Family

ID=29408933

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA2002/000697 WO2003095705A1 (fr) 2002-05-13 2002-05-13 Electrode divisee s'utilisant dans des cellules electrolytiques

Country Status (2)

Country Link
AU (1) AU2002302231A1 (fr)
WO (1) WO2003095705A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3603254A1 (de) * 1986-02-03 1987-08-06 Ht Hydrotechnik Gmbh Elektrolysezelleneinheit
US4839013A (en) * 1986-11-27 1989-06-13 Metallgesellschaft Aktiengesellschaft Electrode assembly for gas-forming electrolyzers
EP1031633A1 (fr) * 1999-02-23 2000-08-30 Ateliers De Monsville S.A. Cellule électrochimique de type filtre-presse destinée à la lixiviation de pulpes contenant des métaux valables
US20020079216A1 (en) * 2000-12-27 2002-06-27 Kirk Donald W. Bifurcated electrode of use in electrolytic cells

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3603254A1 (de) * 1986-02-03 1987-08-06 Ht Hydrotechnik Gmbh Elektrolysezelleneinheit
US4839013A (en) * 1986-11-27 1989-06-13 Metallgesellschaft Aktiengesellschaft Electrode assembly for gas-forming electrolyzers
EP1031633A1 (fr) * 1999-02-23 2000-08-30 Ateliers De Monsville S.A. Cellule électrochimique de type filtre-presse destinée à la lixiviation de pulpes contenant des métaux valables
US20020079216A1 (en) * 2000-12-27 2002-06-27 Kirk Donald W. Bifurcated electrode of use in electrolytic cells

Also Published As

Publication number Publication date
AU2002302231A1 (en) 2003-11-11

Similar Documents

Publication Publication Date Title
EP0080288B1 (fr) Cellule électrolytique de type filter-press
RU2423554C2 (ru) Упругий токораспределитель для перколяционных ячеек
RU2041291C1 (ru) Электролизер
SK363585A3 (en) Membrane electrolytic cell
US4210516A (en) Electrode element for monopolar electrolysis cells
KR101848292B1 (ko) 고면적, 다공성 타입의 유로 내장형 전기화학적 전극 및 이를 가지는 스택형 전기분해 시스템
CA2111689A1 (fr) Cellule electrolytique et electrode a fente capillaire pour reactions electrolytiques produisant ou consommant du gaz, et procede electrolytique connexe
CA2154692A1 (fr) Configuration d'electrodes pour cellules a membrane, permettant d'ameliorer la dissipation des gaz degages
US6527923B2 (en) Bifurcated electrode of use in electrolytic cells
EP0159138B1 (fr) Electrode et cellule d'électrolyse
US20140093811A1 (en) Electrochemical cell having a frame seal for alternative sealing against marginal leakages of the electrolyte
KR860001501B1 (ko) 전극소자 및 그 제조방법
WO2001004383A1 (fr) Procede d'electrolyse de chlorure alcalin
IE840552L (en) Electrolytic cell
EP0118973B1 (fr) Cellule électrolytique
EP0220846B1 (fr) Cellule électrolytique
WO2003095705A1 (fr) Electrode divisee s'utilisant dans des cellules electrolytiques
US4329218A (en) Vertical cathode pocket assembly for membrane-type electrolytic cell
KR20140133301A (ko) 전기화학셀용 막전극 접합체
JP2005504180A (ja) 電極表面を増大した、塩素及びアルカリを製造するための隔膜電解槽、及びその製造方法
FI73008C (fi) Elektrod till elektrolyscell av membrantyp.
JP3069370B2 (ja) 電解槽
CZ279836B6 (cs) Membránový elektrolytický článek
JPS61207589A (ja) 高温高圧用水電解槽の電極

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NO NZ OM PH PL PT RO RU SD SE SG SI SK SL TJ TM TN TR TT TZ UA UG US UZ VN YU ZA ZM ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: JP

WWW Wipo information: withdrawn in national office

Country of ref document: JP