claimed as new is: 1. A method of manufacturing -,t fuel cell eiectrode 60 which comprises intimately and honiogeneously mixing a plasticized -thermoplastic resin, plasticized polyethylene oxide in a ratio based upon parts by weight of said thermoplastic, resin of between 1-3 and 3-1, a powderedelectricahy conductive electrode material selected from 65 the group consisting of silver, nickel, mixtures of silver and nickel, copper, and graphite in an amount sufficient to be dispersed in a continuous phase throughout said intimately mixed thermoplastic resin and palladium oxide to produce a plasticized mass, said thermoplastic resin being insoluble in said polyethylene oxide and alkaline io electrolytes, shaping said mass to produr-e a fuel cell electrade, and converting said palladium oxide to metallic palladium in an alkaline electrolyte. 2. Method o@f claim I wherein said palladium oxide 7,5 is electrochemically converted to palladium,

3. Method of claim I wnerein said ipalladium OXide is cliemically reduced to palladium by means of a reducing agent dissolved in saiid alkaline elertrolyte. 4. A method of maniifacturing a fuel ce-11 electrode which comprises intimately and homogeneoiisly mixing under heat iind press= a plasticized first thermoplastic resin, plasticized polyethylene oxide in a rttio based upon parts by weight @of said first thermoplastic resin of between 1-3 and 3-1, a powdered electrically conductive elec,tro'de mateiial selected from the ;grou-p consi-.,ting of silver, nickel, n-@xtures of silver and nickel, copp@r, and graphite in an amount sufficient to be dispersed in a contintious phase throughout said intimalteiy mixed t-herm(@plastic resin and polyethylene oxide and ipalladium oxide to pro@duce a plasticized mass, said n-iixing being carried out at a toniperature sufficient to plasticizo said resin and said polyethylene oxide and insufficient to degrade said electrode material and said palladiuni oxide, said thermopl,astic resin @being insoluble in said polyethylene oxide, water, and ailkaline electrolytes, shaping saild mass to produw!a fuel ceH electrode, subjecting said electrode to a water bath to par-tially remove said polyethylene oxide from said electrode, and converting said palladium oxide to metallic palladium in an alkaline electrolyte,. 5. Method of -claim 4 wh@erein said electrolde is subjected to a further water bath, following the conversion of said pauadium oxide to palladium to substantially remove said -,polyethylene oxide) from said electrode. 6. A fuel cell electrode compris:@ng a porous conductive matrix of electrode inaterial dispersed in a continuous ph,ase throughout athermoplastic resin, sai-d clertrode material being selecte,d from the group cons@sting of silver, niclccl, mixtures of silver and nickel, copper, and grap,hite, -an ionically conductive gel in the pores of said electrode and palladium entrapped in said gel. 7. A fuel cell electrode for utilization in alkaline electrolytes comprisi@ng a conducti-ve electrode material selected from the group consistin.- of silver, mixtures of silver and nickel, nick-el, copper, and graphi-te uniformly disperse,d throughout apor<)us matrix of a thermoplastic resin insoluble in water and alkaline electrolytes, and having in the pores thereof a gel comprising a polyethylene 3)181,973 6 oxide and said alkal:ine electrolyte and me@,allic palladium entrapped in said gel. 8. Fuel cell cle@ctrode as specified in claim 7 wherein said conductive electrode material comprises metallic silver. 9. Fuel call electrgde as specified in claim 7 wherein said thermoplastic resin comprises polyethylene. 10. Method of manufacturing a fuel jeell electrode which comprises intimately mixing under hp-at and preslo sure one part by weight of polyethylene and one part by weight oj' polyethylene oxide to fproduce, a plasticized mass, intimatejy mixing into said -plasticized niass 16 parts by weight of finely divided silver powder and 1.7 parts by weight of palladium oxide, said mixing being i5 carried out at a temperature @sufficient to plasticize said polyethylene and said polyethylene oxide and insufneieiit to, degrade said silver aird said p@alladium oxide, shaping said niixture to produce a fuel cell assombly, electrochemically reducing said palladium oxide to metalec 20 palladium in a dilute solution of an alkaline elogtrolyte, said akaline electrolyte and said polyethylene oxide forming an ionirally conductive gel vnthin the pores of said electrode assembly. 11. Method of claim 10 wherein said cleotrode is fur25 ther subjectedto a water bath after the reduction of said palladium oxide to p@alladium to leach from said electrode said polyethylene oxide. References Cited by the Examiner 30 UNITED STATES PATENTS 2,38 4,463 9/45 Gun n et al - ------------ 136-86 2,70 8,683 5155 Eise n --------------- 136-20 X 2,73 8,375 3/56 Schl otter -------------- 136-30 2,77 2,322 11/56 Witt et al - ---------- 136-148 X 35 2,80 6,256 9/57 Sniit h-Hohannsen ---- 260-2.5 X 2,81 9,981 1/58 Scho rnstheimer at a]. -- 260-2.5 X 2,83 8590 6/58 Gari ne --------------- 136-30 2186 0',175 11/58 Justi ---------------- 136-86 X 290 2,530 9/59 Eise n ----------------- 136-20 40 2"9 36,328 5160 Sillc ox et al - ---------- 136-145 1 OHN H. MACK, Pi-ii77ary Examiner. JOHN R. SPECK, Examiiier.

United States Patent Office 3@181,973 3,101,973 FUEL CELL E4LECTRODE AND METHOD 0,F IMAIUNG TH'-v SAME Joseph C. Duddy, Trevose, Pa., ass@gnor to The Electric 5 Storage Battery Company, a corporation of New Jersey No Drawin,-. Filed Dec. 28, 1960, Ser. No. 78,833 11 Claims. (C]. 136-120) The present invention gen.-r,.Ily rclates to new and imprc@ved eleetrodes for the dirert prod-action of electrical ]o energy from 'uels by electroirhemical iiie;ans and to methods for n-iaking th-. same. More specifically, th-. p@i@sent inventi on is co@icerned with a new and improved electrode of the type utilizin.- palladiut-n as a catalytic constituent. In my co-pen,@ling apiplicltions, Se,:ial Nos. 818,638 and 15 818,76 6, both now abandoncd, ',Iiere is disclosed a, method for malcing clertro!des inv@rhich a first t@iermoplastic resin, solubl e iii a iven solveiit, aii@l ia second thermoplastic resin, incomi)at-ible Nv-ith the first thermorilastic resin and ilsolu@ ble in the given solvent, a@,-e intimatelyn-iixed under 20 heat aiid pressure to produce a plasticized mass. A-fter the plasticization iTid intensive inixing of the two resins, there is added to 'Lhe plaqticized mass the electrode material in poa,dered fOrM fOT the particular typ-@ o@f - electrode to be prodiiced. After a tim.- iw@erval adeqliate for the 25 thorou gh and homogeneous mixitig of the powder--d elee.j-ode materi-q-1 and the thoririorlast,.c resins, the mixture is shaped as by calendering or extrudin.- to produce material stiltable for elcotrode application. A,,Iter the shapin,- of the material and such other treat-tnpiit as is re- g 0 o,uired to produce the eleccrode, the soluble re-,i@n is leached therefrom by me@ins of a bath in a suitable solvent 1,-avi,lg the etec@Lrode materi@il bound in a permanent m,icro @porous Piatrix of the i-ilsoluble thermoplastic resin. In thes-@ co-pendiig applications the follo@ving resins 35 are disolo:sed as bein.- suitable for utilization as the insoluble resin phase: polyethylene, p,olypropyl---.ic, polystyrene , and polyviryl chloride. The follo,,viii.- water soluble thermgplastic resiiis are diselosed as being silitable for use as the sollible or temporary tbermoplastic 40 phase: polyethylene oxide, pol3lethylene glycol, and polyvinyl pyrrolidone. As a res,,ilt of the inconi-patibility of the thermoplastic r-.sins utfiized in the present invenuion and the - ilitimate wixing and blending the@reif, there is produced a thp-rmo- 45 plastic -Tiiaterial having -,t plurality of int e@@-com-iccted thread 4ike pores of capillary size upon the removal of the soluble resin pl-lase. The pores th-,is formed ire uniformly distribut-,d throtighodt the permanent bizide-@-, crierite d v@ith respert I-o the permanent binder and gener- 0 ally of a size much less than the p-articje size ol- the active materi,- d utilized. Measi-irei-nents have sho-,vn tb-.tt t-lie pores developed by the removal of the soluble resin phase are generally less than one micron in size. As a consequence of the microporosity thus developed and ttic resil- 55 ien--y of the pern-i-@Lqent binder utilized, the electrodes swell -when placed in the leachir..- sol-%,ent. This swering can be attribut ed to the capill,@iry expansion of the porous mat@qx, providi ng for iiiore pore fori-tia:Lion and extreri-@ely efficient utilizat, ion of:Lhe active material. 60 Cat,,ily tically act@iv-- slirface area is an important 'Lactor in controlling electrode perforn-lance. Ore means of achievi ng a maximum catalytic surface area ir. an electrode is to utilize celalytic niaterials havin,@ the finest available particle size and to preserve this particle size during 65 t.he processing of the electrode. Palladiu@n has heretofore been utilized as a catalytic element for increasing the efficiency of fuel eleetrodes in electrochemir-al fliet cell systems. Vvlith respec-t to the utilization af metali@'@c palladium in fliel cell electrcdes, it is proposed to utilize pal- 70 ladiu.,ii oxide as a stiirting material for the prodliction of fuel electrodes inasmtich as that oxid-. is aviilable coniPatented Miy 4, 1965 2 iiiercially in a much finer par@ticle size than is the metal its.-If. Palladium oxide is in fact avail@able co.,iiniercially in a iiiieness whicii may be b,-st charact-.Tized as impal@pable. When pallaCi,,@,n-i ox'de is ritilized in electrodes manu-fact,,ired in accordaiic.- with the teachina of the fore. rogoing pe@iding Lppl'cations, ho'@Never. it has been found that the interstit,-,il pores created ther,-;n by the remo-,/al of the water soluble res-irou@- phase, even thou,@h they are of an avera@,,-- Llimension of less than on-, micron, are nat slifficiently sn-iall to imp,- de the removal thercwith of the palladium o.-,iCe particles which,are sniall enough to b-- come colloid@ally suspended in the leachin.- w@,iter and lost frorn the electrode. This situation is par6cularly unfortuna!Le inasmuch as the extremely f-@n.- partirles which diffuse throu,-h the interstitial n--tworl?- Pnd so becoine lost ar,- the particles wb-icli, beca-,ise of their extremely fine size, are the most catalytacedly active. It is @Lliercfore an object of the present invertioii to provide a me,aiis for Dreventing the re@noval of siieh part@icles of palladium oxiae frbni the relsiiotis n,-twork described and in so doin- to provide a fiiel electrode - characterized by ele--trc-.bemical efEcienc@'@e3 ol an extremely high order. , he essence of the present i,.i@vention is associated with the unique pH characteristics of one of the water soluble resii phases specified in the aforenientioned co-pending tpplications. This resin, pelyethylene oxide, is readily and complete y soltible in solu ons havinc, a p'rl in the are@i of noticrality; however, in -inereasingly acid or alkaline aqueoiis soltjions it b-.comes inereasinglir less soluble. The insol'ab; ity o n tio-@is is ch@aracterized by -ne oxi in a ine solue formatio-ii of a @el attended by the swelling of th-, resins caused by the absorption of the alkali-@ic solulion. In this -Clled stat-I the solvated resin is capable of supportin.- ionic cond-Lictivity by virtue of the absorbed solution. in additioi, in strongly alkaline solutiori@- of the type -Lljtilized for fuel cell electrolytes the gel formed by this resin and the alkaline soliition is not physically gelatino,,is in nnti-,re, but is seini-resinous in natlre. Th-. pre@.ent inve-@ition is c7naract-,rized by the titilization of these, unique prop.-rties of polyethylc,.qe oxide to imni-,Ibilize v,,ithin the pores of a fuel cell electrode minute particles of palladiuin oxide until they a-re redr,,ced to@ ri-ietallic palladium @to provide a fael cell electrode charactelized by moderate co,st and high efficiengy. Other objects and advantages of the present invention w-il'i be apparent from the followin.- detailed description of preferred embodiments thereof. In carryin- out one form of the present inveiltion a fuel cell eiectrode is produced by intimately mixing under heat and pressure 1.0 part by Nvei.aht of polyethylene cxide and 1.0 part by weight of an insoluble tliermoplastic resixi such as polyeth)Tlene to produce a plasticized mass. The ititiniate mixing of the two resins may be accomplislaed in an iitensive mixer or an extruder, bi:,t preferal,)Iy is acconiplished on a two-roll rubber mill in which the rolls are operated at differeiitial speeds. A temperature ol abolit 275' F. has been found applicable for plasticiziiig the two resins. After the plasticization and i-,lt,"mate admixin.@ of the two resins has been accornplished tiiefe is added to the plasticized mass on the mill 16 parts by weight of j'inely divided silver p6wder and 1.7 parts by wei,@ht of impalpable palladium oxide. After a tinie, interval ad-,quate for the thorough and intimate iiiixin,@ of the powdered silver and palladium oxide into th-- ti-icrq-ioplast;c resins, the mixture was removed from tLc m:@ll and pellet;zed at room temperature for subsequent shaping as by cale-@iderin.- or extrudir@g. Tb@-s-@ skilled in the art will understand how to select the t:ir@e required for pl@asticizin,@ the thermoplastic resins and also the tir-iie required to produce the intimate mixin.a described above. When the mixing of these niaterials is

accomplished on a two-roll mill, a time order of about two to three minutes is satisi'actory for plasticizing and mixing the res:@ns Pnd a time on the order of about seven minutes is satisfactory for the mixing of the powdered metals into the plasticized resins. Th,- pelletized mixture of thermoplastic resins and ciectrode materials is n.,xt fed to an extruder and extruded as a diameter rod onto a 1,62" diameter s-ilver wire which serves as a coliductive core. For this purpose, a temperature of about 225' F. has been found to be a satisfactory temperature for extruder operation. Followin.- the s'iiaping of the electrode, the palladium oxide therein is electrochemically converted to palladium in a dilute solution of potassium hydroxide against a suitable electrode. For this purpose, a 7% solution of potassium hydroxide may be utilized and the palladium oxide electrolyzed cathodically against a nickel electrode and coiiverted to palladium. Because of the dilute nature of the alkaline electrolyte utilized, the polyethylene oxide phase of the electrode readily absorbed tb@- electrolyte and swelled to form a gel therewith in situ. By virtue of the absorbed electrolyte this gel was capable of supporting the ionic conductivity necessary for the reduction of the palladium oxid-- to palladium. It should also be noted that the in sitit swellin.@ of the water soluble resin phase was accommodated by the resiliency of the insoluble resin phase of the binder utilized. Following the reductioil of the palladium oxide component of the electrode to palladium the electrode was ready for utilization. The particular electrode described was adapted for use as a fuel electrode for the production of electrical ener.-y from a liquid fuel, such as alcohols, keto-@ies, end ethers, which are miscible in the electrolyte. By way of example, this electrode was operated successfully as the fuel element in an alcohol-oxide fuel cell system. The electrolyte utilized coniprised 10 parts by weight of ethyl alcohol and 90 parts by weight of a 27% solution of potassium hydroxide. At a current density of about 40 amperes per sq. ft. at roomtemperature, the polarization of the electrode was only 420 millivolts. It should be understood, however, that in a differ,- -nt physical configuration such an electrode would be applicable for use in fuel cell systems other than those in which a liqiiid fuel is mixed with the electrolyte. Thus, a fuel cell electrode in accordance with the present invention is suitable for use as a gas electrode where the gas is applied in countercurrent relationship to electrolyte penetration. In accordaiice with the present invention the palladium oxide also can be chemically reduced by immersion of the electrode in a suitable reducing agent. For such treatment the soluble resin phase must be partly solvated in order to develop the porosity necessary to facilitate penetrat,'on of the reducing agent. By way of illustration, the electrode after shapin.- can be immersed in a solution of alcohol and potassium hydroxide. Since the electrode swells with the absorption of the potassium hydroxide by the soluble resin phase, to form a gel, porosity is developed which permits the reduction of the palladium. Another method which has been found applicable for treating an electrode in accordance with the present invention is to partly leach the water soluble resin phase from the electrode in a water bath. While the time interval necessary for such treatment is primarily determkied by the physical configuration of the electrode it should be understood that the leaching process must only be carried out partly to avoid undue loss of palladium oxide from the electrode. For an electrode of the type described hereinbefore, a soaking for a time on the order of 10 minutes was found applicable. Following the soaking of the electrode in water, the electrode may be transferred to an alkaline solution and the metallic palladium 6onverted to palladium oxide electrolytically. It should be noted that following the reduction of the palladium oxide to the metal,, the complete removal of the soluble resin phase 4 from the electrode can be accomplished in a Nvater bath w;Lhotit loss of the palladitim from the electrode. While the rilechanism which prevents the loss of the palladium frori-i an electrode in the water leaching bath, but permits the loss of palladium oxide from an electrode under the same conditions is not fully understood, it is believed attributable to the different surface char.-c characteristics of the oxide and the metal. Accordingly, once the metallic palladium has been converted to the metal where de10 sirable, the soluble resin phase can be removed entirely from the e!ectrode leaving the metallic palladium deposited within the pores of the electrode. Tho teachings of the present in-vention are applicable to electrode incorporating materials other than silver. 15 Thus, other fuel cell electrode materials such as silver @and nick-el, nickel, copper, and graphite can be used in co-.nbination with palladium oxide. The porosity of electrodes made in accordance with the present invention can be controred by varying the amount of the soluble resin 20 phase utilized with respect to the insoluble resin phase utilized. It has been found that optimum electrode performance is achieved where the soluble thermoplastic resin is present in amounts varyin- from approximately 1/3 the amount of the insoluble resin to tlirce times the 25 -,imount o'L the insoluble resin. It should be understood that the specific electrode formulation cited hereinbefore is by way of example only and is riot necessarily that which provides optimum electrode performance. While polyethylene has been cited as an example as a resin suit30 able for use as the insoluble resin phase, it should be understood that polypropylene, polystyrene, polyvinyl chloride, and other thermoplastic resins which are insollible in water and electrolytes, incompatible with @the polye-thylene oxide, and which can be plasticized at tem35 peratures which will not degrade the water soluble resin phas.- or the eleetrode material, wiR be suitable. By incompatible is meant that the two resins will exist as separate and distinct phases in the plasticized state. The amount of electrode material with which the 40 thermoplastic binders can be loaded depends piimarily upon the particle size of the electrode material utilized, As a general rule, it has been found that the amount of loading which can be achieved will increase as the size of the electrode material particles increase. In this re-,zpect hoivever, it should be noted that for fuel ccli elec45 trode applications, increased loading does not necessarily increase electrode performance since electrode perfomiance is govemed primarily by the catalytic characleristics of the electrdde material utilized and the availability of that material for providing sites at the fuel electrolyte interface for the cell reaction. The present invention provides a mean6 for making available palladium derived from pauadium oxide asthe catalytic elem-,nt in fuel cell electrodes made by the manufacturing method which uti55 lizes a water soluble resin phase in combination with an insoluble resin phase. Havin- described the present invention that which is