CA1281744C - Fluorinated carbons and methods of manufacture - Google Patents

Abstract

FLUORINATED CARBONS AND METHODS OF MANUFACTURE ABSTRACT OF THE DISCLOSURE Discontinuities, edge sites and grain boundaries in carbons. the primary locations of instabilities for oxidative corrosion and degradation, are prepared by preoxidation to form carbon-oxides followed by highly selective and relatively mild fluorination to specifically substitute carbon - oxygen functionality with stable carbon-fluorine groups. The novel fluorinated carbons have enhanced chemical and/or electrochemical stabilities to corrosion, improved hydrophobicity, lubricating properties, etc.

Description

" 1,~81744 FLUQBINATED ARBQNS AND M~THODS QF nANUF~CTyR~

BACXGBOVND QF THE INVENTION
The pre-ent lnvention relatsa to novel fluorinated c~rbona, ~nd Qore spf3cific~11y, to improv,,~,d ~morphou~, cryst~lline ~nd gl~J~y or vitreoua fluorin~ted c~r~ons, products m~de therefro~
~nd methoda of m~nuff~ctur~
C~rbona, which lncludos both amorphoua and cryatalline types liko c~rbon ~ ck~, l~p black, graphitic ~nd pyrolitic typeQ, to n~e but ~ few, find U60 in ~ ~ultitude of i~port~nt ~nd often crltical applicatlona in ~odern t~chnology r~nging from motor bruffh-~, lubric~nt-, b,attorie-, fuel Cell8, plostlc rofr~ctorios, ho~t oxch~nger-, composites, nucl~ar genorators, r-aiatora, oat~lyst support~ ~nd ~o on A ~Jor ahortcoming, howf~3vf~3r, in ~ny spplication- for carbon~ 18 often the llmit-d useful llfo aa I :, r-~ult of oxidative dogr~tion ~f~ ~One aolution to tho probl-~ of oxldativo degr~tion ha~ been , ~, ~, , tho dlreot fluorln~tion of o~rbon with ~ ental fluorine Dir-ct fluorin~tion ~ethod- ~r- di~olo-ed by W ,~ T-t-r l ~l in - U S Pat-nt 2,786,874 <1957), J L Margrav- ln U, S Pat-nt ~; 3,674,~32 ~1972~, D T M-shri et Jl in U S P~tont 3,92~,918 1975~ and T, K~o t ~l $n U S P~tent 3,''~29,920 (1975~
F1uorogr~phite~, for ox~pl-, pr~spar-d by the, diroct luorln,ltion ~ethod ~re typically hydrophobic, poAsoss hlgb t-~p-r~tur- tabillty, ~re in-oluble in or~anic ~sol~snt~ and aro r-l~tlv-Iy unr-~ctive, b-ing att~ckod neithor by strong acids nor by alkali-- Th - y ~ay bo repr~,~ae~sntod e~pirically a~ <CFX~n , ,: :
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~8~744 where their specific prop-rties depend on the v~lue~ for x ~nd n ~luoro~r~phites, for inet~nce, in the r~nge of CFo 5 to CFl ~ ~re uaed in lithium CFX b~tterlea ~s positlve electrodes Those b~tteries posoeo~ ~ high energy density of 320 to 470 w~tt hour~kg, ~ hi~h open circuit volt~ge of 2 8 to 3 2 Yolts, ~ high working volt~ge of ~bout 2 6 volts ~nd ~ long shelf life However, the u~eful r~nge of fluorogr~phite batteries prep~red by the direct fluorin~tion method i8 limited bec~u-- a~ v~lue- for x incre~se roa~istivity ~re~tly incra~sos In f~ct the highly fluorin~ted mat-ri~l ~Fl l is ~lmost ~n insul~tor or nonconductor Not only la fluorogrsphlte, for exsmple, msnuactured by 8 costly som-wh~t h~z~rdous proce~ by direct fluorin~tion with fluorine ga-, but frequontly undergoes degrad~tion in the proce-~ Strong, highly r-active fluorin~ting agents, such ~8 l-m-nt~l 1uorine, ClF3, ClF, CoF3, etc , have ~ tendency to produo- nondiscrimin~ting re~ctions with c~rbon molecules even c~u-ing fr~gment~tion of edge sites, gr~in bound~ries, di-loc~tion~ and oth-r sur~aco imperfectiona Strong, nons-l-ctive fluorin~ting ag-nts t-nd to fluorin~t- olefinic and ~rom~tic c~rbon to carbon uns~tur~tion 4itos, ~dding to the lay-r-d plane- of b-nz-ne rings of the molecule to provide nonconductlve carbons Accordlng to tho preaent invention, it waa di-covered th~t "aoft" fluorin~ting ~gont- ~re more s-lective in their Dtt~ck of ; function~l groupa showin~ loas t-ndency to degr~de ~nd fr~gment:
dge ites, gr~in bound~rie-, etc , th~n strong fluorinating 1~81744 ~ents, like element~l fluorine Th~t is to ~y, it wo~ iound th~t fioft fluorin~ting ~ent~, liko SF~ will not ro~ct with c~rbon to c~r~on olefinio ~onds in c~r~on structures, but in~te~d react wlth c~rbon-oxygen bonda to rep1ace oxygen wlth fluorine ~t edge sites, gr~in boundariea, disloc~tions and other ourf~ce imperfection~-, which ~re ~180 the s~me cite~ where oxid~ti~e ~tt~ck of c~rbon~ u~u~lly occur Accordingly, it W~5 po~tul~ted that if most potentially oxidation ~enoitive regiona of carbon ~tructures could be selecti~ely fluorin~ted st~bl- gr~phite ~nd othor carbon~ could be prepared with greatly i~proved life expectancie~ whilo rot~ining their de~ired therm~l ~nd electric~l proportie-A C T-ter in U S Patont 3,340,081 recognized the incid-nt~l pr-~-nce of ~urfuce oxygen in co~merci~l c~r~on bl~cka How-v-r, T-ter friled to recognize the beneficial effect o p-cifically pr-treating carbon blacks boforo fluorination to flrat d-v-lop moat of th- ~ite- o potential in~tability to oxid~tiv- corro~ion ~nd degr~d~tion In~te~d, without further oxid~tiv- pr-tr-~tm-nt, T-t-r proae-ded directly to fluorin~te comm-rci~l c~rbon bl~ck with 5F4 or other or~nic ~ulfur trl1uoride fluorinating ag-nt to a ~aximu~ level of 7 percent by woight fluorino to pr-p~r- roinforcing ~gonts for butyl rubbor vulG~niz~to~
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~ ccordlngly~ on- aspect of th- pr-aent lnvention relates to ,~ novel fluorln~t-d ~morphous ~nd Grystalline carbons and methods of ~nufacturing auch c~rbon~ which h~ve longer life ` exp-ct~nGie-, yet ~t-ri~lly preeerve their desir~le th-rm~l ~nd f"`~ el-ctrlcal properti-- By developing e~sentially all such ~ 3 i, ' ,~

1~1744 potenti~l ~ites of oxid~tivo corroaion ~nd de~r~d~tion prior to fluorin~tion, cnrbons h~ving hiyher levelc of fluorin~tion c~n be prep~red ~t rel~tively low co~t by lesc h~z~rdous ~p~cific fluorlnation method~
Fuel cells require the uce of ~c ~ir or oxy~en~
dep~l~rized electrodes which ~re oomprised of hi~hly aophistic~tod mixturea of ~rious c~rbona, c~t~lycts ~nd polymers, ~long with other ~dditive~, ~nd supportive ~tructures which m~ke up ~ aolid compoaite olectrodeA The succesaful oper~tion of ~ fuel cell electrode i~ ~o~erned by e~t~blishing thr-~-ph~-o interf~co ite- 908 (u-u~lly oxygen or ~ir~, lectrolyte aolutlon ~oft-n ~queoua ~cid or b~se) ~nd the aolid co~poaito l-ctrode However, ~fter extended uae, depol~rized c~rbon ol-ctrodea tond to b-co~- oxidized, lose their hydrophobic prop-rti-~ ~nd "flood" when lectrolyte penetr~tcs into their poroua tructur-s Electrolyte solution i5 dr~wn further into th~ ctrode atructure with v-ntu~l depletion of the useful thr---ph~a- intorfuc- sit-s Furth-rmoro, once floodin~ hus ocorrod th- probl-m ia oft-n irr-ver-ible ~nd the fuel cell b-co~-- lnop-r~bl- Thia surf~c- oxid~tion of c~rbon~ ~nd t-ndency to tr~n-fora from hydrophobic to hydrophi~ic proportiea i~ ~lao ~ proble~ in ~et~l ~ir b~tt-rios, e~ zinc-~ir b~tt-rios ~ , ~
~nd ln bifunctionol ~ir l-ctrod~a Tho problem is eapecially -v-r- in blfunction~l ~ir lectrod-J, ince in this inat~nce the g~a diffuaion l-ctrod- ~ct~ n oxy~-n-evolvin~ olectrode in th- ch~r~- st-p ~nd is further oxidized TQ ovorc~mo theso ~; problo~, workers h~ve Jou~ht to u~e ~ore st~blo c~rbons liko ii .
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: : -:' ~ ,: ' , lZ8~744 ~r~phite c~r~ona prep~red under speci~l condition~ ~t high temperaturea Cat~lyAt~ have also boen in~orporAted into compoaite electrode structures to destroy peroxide spocioa, which form to ~ome extent with reduction of the oxy~en or ~ir feed, ~nd which ~ccounts for eome of the oxid~tive de~r~dation of c~rbon aurfacea Accordingly, ~ ~urther aspect of the preAent ~nvention is the prep~r~tion of improved fluorin~ted c~rbon composites, lncludlng fuel cell electrodea, metnl-~ir bQtterLee and bifunction~l ~lr electrodeA The improved fluorin~ted curbon~
~ore efectively protect sitea on the c~rbon eloctrodes which would otherwise be prone to floodin~ ~nd ~ddition~l de~r~d~tion Th- pr---nt invention ~lao provides o method for regenerating ~p-nt-flooded g~a dlffuaion lectrodoa for reuae by apecific 1uorin~tion, ~4 d-scrib-d in further det~il below It h~s ~een known for munr ye~rs th~t ozone, 03, could ~e produced oloctrochemio~lly using v~rious kinds of ~nodes, eg le~d dloxlde ~nd pl~tlnu~, in cold ~c1dic electrolyte aolutiona, lik- ~ulfuric ~cid ~nd phoaphoric ~cid In most c~ses, however, th- nergy conv-raion offici-nciea wer- found to be low More r-c-ntly, Foll-r et ~1 reported ln CEP ~49-51), M~rch 1985 th~t ozon- could bo g-n-roted ~t much hlghor current efficienciea using vitr-ou- or ~ y curbon ~node- in ~ 48 percent ~queou-t-tr~fluoborio ~cid olution In spite of the ~pp~rent ~dv~nt~g-- of lectroch-~ic~l ozono ~-nerDtion with ~itreous carbon ~nod-s their xpo-ur- to hlghly corroalvo ~cidic lectrolyte- h~- b--n found to shorton thoir useful life xpect~nci-s, m~king thom ~ le~a ~ttractiYe ~ltern~tive ';: S
,' , ~81744 Mor~o~r, curr~nt ~ffici~ncio~ for ozone ~re ~till too low ~nd uneconomic~l for msny ~pplic~tions Accordin~ly, a further ~pect of the pr~ont in~sntion~
rel~tes to the discovery th~t fluorin~tion of vitreous or glQ~y c~rbona resulta in - m~teri~l which i~ con3iderably more ot~ble to corrosion in cold ~queous ~cids, including ~ulfuric, phoophoric ~nd tetrafluoboric acida ~kin~ such c~rbonn currently ~ore auitable ~nd economic~l ~ ~node~ ln the olectroche~ic~l gen-r~tion of ozone ~8 well ~a for other uaea ~n ~node~, ouch 8S
per~ulfsto for~tion SUh~ARY OF THE INVENTION
Tho pre~ont ln~-ntlon r-l~te- to apecific~lly fluorin~ted c~rbons ~nd ~othods of ~nufscturo, including specifically fluorin4ted s~orphous, cry~tsllino ~nd ~itreous c~r~ono~ The fluorln~t-d c~rbon~ ~r- ch~r~cterized by improved chemic~l ~ndJor ctrocho~lc~l stsbllltio~ to corro-lon, onh~nced hydrophobic prop-rti-s, lubric~ting prop-rti-s, ch-~ic~l ond el-ctroche~icsl o~t~ly~i~, snd support structur- for d-posited cntuly~ts, whilQ
~elnteinlng 811 or vlrtu~lly ~11 th- d-~lr~ble phy-ic~l ~nd ch-~ic~l prop-rti--, g thor~sl ~nd l-ctricsl conductivltio-, for which 8 psrticulsr osrbon or gr~phite w8s ohoson Aocordingly, th- fluorinstod o~rbon-, smorphous, cryst~lline snd ~itr-ous typ-~, sro sd~ptsbl- to ~ wide r~nge of ~pplic~tions whlch t~ko sd~ntsgo of tho-- proporties, auch sa in fuel c~
bstt-ri--, p-cislty eleotrQdos, cst~lyst supp~rt~, lubriosnto, lin-r- for ohe~iosl r-sctor-, tructursl co~pooitos with ~otsls ' - , .
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~ ' 1~81744 and polymers for nuclear reactors, heat exchangers and seal rings. Many of such applications take advantage of both the surface and bulk chemical and physical pro?er-ties of the carbons.
The specifically flucrinated carbons are prepared by preoxidizing discontinuities, edg~ sites and grain boundaries to form carbon-oxide grou2s at essentially all primary sites of oxidative instabiliLy on the carbon structure, followed by highly selective and relatively mild fluorination of the preoxidlzed carbon with a "soft"
fluorinating agent, such as sulfur tetrafluoride or any other fluorinating agent capable of specifically substituting carbon-oxygen functionality with carbon-fluorine groups. Thus, the invention contemplates fluorinated carbons having fluorine covalently bonded to discontinuities, carbon edge sltes and grain boundaries of carbon structures. By contrast, sites of oleLinic and aromatic carbon-to-carbon unsaturation, including carbon basal planes in more structured graphitic type carbons are substantially free of such bonded fluorine.
~ Thus in accordance with one aspect of the inven-tion a method of fluorinating a carbon comprises the steps of preoxidizing the carbon, and fluorinating the preoxidized carbon by specific fluorination. In one , ~ .

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1~8~744 embodiment this method is employed in a method for extending the useful life of a vitreous or glassy carbon electrode.
In accordance with another aspect of the inven-tion a method of regenerating an oxidized or flooded carbon-containing electrode comprises the steps of cleaning the electrode and specifically fluorinating the cleaned electrode.
In accordance ~-ith still another aspect of the inventionthere is provided a preoxidized, specifically fluorinated carbon or carbon substrate. In one embodi-ment the fluorinated carbon or carbon substrate has a fluorine content of at least 8 percent by weight fluor-ine. In another embodiment the carbon is activated carbon, glassy carbon, soot, charcoal, or crystalline carbon.
In accordance with yet another aspect of the invention there is provided a specifically fluorinated carbon or carbon substrate post fluorinated with a moderate or hard fluorinating agent. In one embodiment of this aspect of the invention the specifically fluorin-ated carbon or carbon substrate is preoxidized and post fluorinated with such fluorlnating agent.

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~317~4 In still another aspect of the invention there is provided a specifically fluorinated vitreous carbon, glassy carbon, crystalline carbon or carbon substrate comprising a crystalline carbon.
In a particular embo~im~nt of the invention ther~
is provided an electrode which comprises a specifically fluorinated carbon; in one embodiment the specifically fluorinated carbon is preoxidized; in another embodiment the electrode is a battery electrode. In a particular aspect of this latter embodiment there is provided a battery comprising an electrGde of the ir.vention.
In a particular embodiment of the invention, amorphous carbons and crystalline carbons are fluorinated with a soft fluorinating agent to a fluorine content up to about 20 percent and 10 percent by weight, respec-tively, however, the mildly fluorinated carbons can be fluorinated to even higher levels by post fluorinating with "hard" fluorinating agents, like elemental fluo ine which add to sites of olefinic and aromatic carbon to carbon unsaturation.

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i.~8~744 DESCRIPTION OE THE PREFERBED EMBODIMENTS
In accord~nce with the present invention, corbon~ ~re preoxidized to more fully de~elop potenti~l fiit0a O~ inet~bility with the ultim~te o~eGtive of protecting thoee region~ with stable carbon-fluorine bond~
Carbons found moat auit~ble for use ln accordance with the invention are selected from ~morphous or microcryet~lline ~nd cryat~lline typea Amorphou~ c~rbon is intended to me~n imperfectly ordered molecular atructurea having rel~tively high surface areas, and whlch may alao po~sess ~ome incidental reactive oxygen sitea Here, pl~nea of ~toms ~re l~yered, irregul~r and unoriented without extenoive growth in any dlroctlon Crosa-linking between the planea accounta for their greater hardne~a and mechanical ~trength compared to graphitic structuree which l~ck cross-linking of pl~nes ~ontrolled he~ting c~n oten convert them to gr~phitic a~rbons Amorphoua carbona include carbon blacka, like lamp black, thermal bl~ck, ch~nnel black, acetylene black and furn~ce bl~cks Other ~morphous curbono include ~ctivuted c~rbon~, vitreou~ or gl~ay c~rbons, ch~ra, aoot, ch~rco~l, and the like They are commerclally av~llable in varioua forms including powders, woven c~rbon~, felt-, c~rbon flbera, to name but ~ few In contr~t to ~morphous type c~rbons ~re the cryst~lline or gr~phitic type c~rbons~ eg gr~phites ~nd pyrolytic graphites, which exhibit ~ more ordered molecular structure, closer spucing b-tween monopl~nes and ~t~cka and relatively low aurf~ce areaa, ~nd thorefore, h~ve gre~ter Gt~bility to oxid~tion They h~ve subst~nti~lly ~-tter electric~l ~nd th-rm~l conductivities th~n 1~8~744 ~morphoua c~rbons ~nd are ~v~ ble ~- powdor~, woven moteri~ls, f~lt~, fib~ra ~nd othor forms Th- present inYention contempl~tes fluorin~tion of ~irtu~lly all ~orms of c~rbons, lncludlng powders, ~ibera, fl~kes, ~- well ~a aolid m~se~ of Qny cryat~llogr phic orient~tlon, cryst~llite aize, interl~y~r ~p~cing, intoratomic dist~nGe, den~ity, poro-ity, p~rticle ~izo or sh~p~ How-~-r, th- fluorin~tion methods of thi~ ln~ention extend beyond c~rbona per ae, but c~n ~lao bo uaod ln 1uorin-ting v~rious "carbon sub~tr~tes", which term is intended to me~n c~rbon containing m~teri~ls ~nd ~rticlea llko c~rbon ste-l- which ~r- ~lloy~ of iron In c~rbon rte-ls or mlld steel- c~rbon i~ th- most lmport~nt ~lloying elem-nt ~lthough auch ste-la u-ually contnin 1 - 8S th~n 1 5 weight percont c~rbon Composit-o ~r- ~lso includ-d within th- me~ning of the oxproseion "c~rbon aub-tr~te6" Composite- ~ro intonded to ~e~n two or ~ore chomlc~lly distinct ~st-ri~ls wlth ~ distinct int-rface a-p~r~tlng th- componenta Co~poaites uau~lly compriae c~rbon or gr~phitic fibors or cloth ~- ~ r-inforcing ~g-nt in ~oro ductil- ~strix, uch s- epoxy or othor resin or pl~atic ~at-rl~l, although ~ ~-t~ trlx c~n slso be ~ployed Csrbon or graphito powd-r- c~n alao b- us-d in compositios in which two different form~ of o~rbon ~r- us-d in the s~e structur~l unit 9olid o~rbon- ~nd gr~phite-, such ~s l~ctrodos ~re ~180 o~rbon sub~tr~te- within the m-~nlng of the foregoing d-finition ~tre~t~blo ~ccording to tho prea-nt invontion~ Electrod-- ~y b~
formed by high t-mper~ture ~intoring of o~rbon or gr4phite powders, fl~k-~ or othor c~rboniz~bl- m~teri~l~ with binder~, .~ ~

' ~8~744 like oil, pitch or t~r Theae m~terid a ~re firat mix~d snd thon extruded, shaped or molded ~nd then fired to a temper~ture to c~rbonize th~ binder Further firing ~ hi~her temper~ture~ m~y al8o be carried out to gr~phltlze the m~ss The ~olid ma~ will usually be aub~t~ntl~lly porous, which can be reduced by impregn~ting with ~ carbonizable m~teri~l and then fired Becauae of th~ broad variety of carbona and carbon-substr~tes ~uitable for fluorination according to the prosent invention there may ~e wide differences in the level of ohemically ~onded fluorine Fluorin~tion occur~ ~t the ed~e sites of pl~nes and ~t i~perfections on surf~ce l~yer~ ~dge and plane defecta are more nu~orou~ in the ~morphoua carbons, eg, oh~rco41, coke ~nd th- carbon bl~oks than in gr~phitic carbons As ~ re-ult, the amorphou- c4rbons ~re moro re~dily fluorin~ted than graphitic c~rbon~, ~nd can be fluorin~ted to higher level~
than cry-tollln~ carbon~ Pyrolytic graphite has a n~ar perf-ct cry-t~l structuro and will have low l-vel- of bonded fluorine Carbon bl~cks for purpo~es of the pres-nt invention will be p-ci1cally 1uorinat-d to o ~inimum of at leaat 8 percent by welght fluorln~, and ~or- partlcularly, fro~ 8 to about 20 p-rc-nt by w-ight Othor amorphous carbons, 9 ~ctivated carbon-, char~, coke, vitr-ouJ or glnssy c~rbons, etc in powder for~, cloths, f-lt-, fib-rs, c~rbon substrate~ and th- like will b- fluorlnat-d to at lea-t 0,1 p-rcent by weight, and ~ore particularly, from ~bout 0 1 to about 20 percent by weight In th~ c~se of cryst~lline carbQns~ they will be speci~ic~lly fluorin~tod to at le~st 0 07 p-rc-nt by woight fluorine, ~nd ~ore partlcularly, fro~ about 0 01 to about 10 percent by w-ight : 1~

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~8~744 The expression~ - - ~peclfic fluorin~tion or specifically fluorinated carbon - - for purpo~e~ herein are intended to mean fluorin~tion of c~rbons ~t loc~tions of inst~bility, eg edge ~ites, dialocatione, gruin bound~rles and other ~lmll~r reglon~
a~ they occur ln carbon atructures, which locutlon~ have carbon oxide function~lity selectively fluorinated to form st~ble c~rbon-fluorine bonds there~t Specific~lly fluorin~ted c~rbons ~y bH form~d by the st~ps of preoxidizing pot~ntiDl ites of in~t~bility to form carbon-oxide surf~ce~ The preoxidized carbon or carbon substr~te i~ then fluorinated with a "soft"
fluorin~ting ~g-nt to convert these c~rbon oxide group~ to st~ble 1uoroc~rbon bond~ thereby protecting these otherwise un~table ~lt-- Thu~, for most mbodiments the lniti~l atep of tho inventlon provld-- or developlng the unstable slte~ and rogion-by oxid~tion to form c~rbon-oxide aurf~ces As uaod herein, the t-r~- "oxldation" and "preoxld~tion" wlth r-~poct to corbon urac-- aro intendod to mean the apeclfic dev-lopment of ~ites of pot-ntial in-tability to oxidative corro-ion and degr~d~tion in c~rbons ~nd c~rbon aubetr~t-s by formin~ re~Gtive oxid-s th-ro~t ~t l-vels in xces- of those pros-nt b-foro such dov-lop~-nt It is ~l-o to be underJtood, th- term - - surfoc-s - - wlth rog~rd to the tcp- of preoxid~tion and p-cific ~luorin~tion ls not int-nd-d to b- limited to the outer~o-t l~y-r- of tho c~rbons but ~y ~lso include interior ~ub-tructur-s, d-p-nding on the typ- o carbon, den-ity or degree of poro~ity of the ~at~rial being tre~ted veloping the potenti~l ite- of inst~bility by . ' .
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1~81744 preoxid~ti~n c~n bo p~rformed chemieolly or eleetroche~ie~lly ~hemic~1 oxid~tion methode are c~rriod out by immer~ion of the earbon or earbon aub~trate in Aqueous ~nd non-~queou3 oxidizing ~olutiona, cont~ining ~uch oxldizing Qg~nta ~a nitrlc acid, pota~slum perm~ng~n~te, aodium hypoehlorite and ommonium per3ulf~te Chemlc~l oxid~tlon alao includea th~rmal methoda where the c~rbon i5 he~ted in the presenee of oxy~en, ~ir or c~rbon dioxido Chemic~l oxid~tion of c~rbon h~o ~een do~eribed by H P Boehm, et ~l, An~ew Che~ Intern t Edit, ~,~69 ~1964 and, Anor~ Chem 353,236 ~1967) In ~n ulternoti~- ~ethod ,corbon~ c~n bo electrochemic lly preoxidized, for ex~mpl-, in 15 percent ~queoue ~ul~urie ~eid by pol~rizin~ the corbon ~nodicDlly Eloctrochomic~l oxidoti~n of earbon la do~erlbed by N L Welnb-rg, ~nd T B Reddy, J A
gl-ctEoehemistry 3,73 (1973~ Ualng ueh methoda, the prineip~l earbon oxide sp-eies for~ed are the trongly ueidlc earboxylie aeid, w-akly ae~die earboxylie aeid, phenolle hydroxyl and earbonyl group~ The el-etroehemieal method of earbon oxlde formation i8 g-nerally preforr-d ovor the ehomleol mothod for lootrodo u--- bee~u~- of b-ttor reproduei~ility ~nd convenienc-In treatiny earbon-, th-y ~re usu-lly preoxidized to furthor dev-lop ~o-t or e-sontlally all the potential altea of in-t~bility Howev-r, ut minimum th- e~rbon i4 oxidizod ~t le~st to ~ l-v-l of oxidution con-i~t~nt with the dosired lovol of 4p~eifie fluorinution Thu~, eh-mie~l or eleetroehemieul preoxidation 1- eondueted to a levol, ~ueh that apeei~le fluorln~tion with, eg sulfur t-tr~fluoride, providea e~rbons generally with about 0 1 to about 20 pereent by weight ~luorlne ~: :

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, Tho~e ~a~bon~ like c~rbon blacks hDv~ng eome lncidont~l ro ctiv~
oxygen aites ~re preoxidized to more ~ully develop potenti~l ~it~s o inst~bility Th~t is, c~rbon bl~ck~ for inst~nce havlng 5 percent by weight 4urface oxygen will be developed to at least 8 percent by weight ~nd sub~equently fluorinated to convert the c~rbon-oxide groups to stable fluorocarbon bonds A~ ~ furth~r ~poct of the in~ention, in c~rtnin e~bodim-nte tho preoxid~tion step is performed in-~tu, and th-r-foro, aeparate tep for developing all potontial eites of oxidative corroeion and inet~bility can b~ omittod Th~t i~, in rsgon-r~ting ~pent electrodos, for xa~ple, a c~parste oxidizing ~tep to fully dovolop the odgo ~ite~, gr~in bound~ries, tc , prlor to fluorlnation c~n b- dl-penaed wlth b-cauee the electrode urfacoa were oxidized ln tho cour-- of regular ue- Oxidation of th- el-ctrodo urfacos cau-ed the~ to become hydrophilic ~nd to flood Honco, ess-ntially all pot-ntlal itee have boon fully d-velop-d in--it_ during u-e~ and th- epont el-ctrodee can be r-g-noratod by p-cifically fluorinating with a soft fluorinnting a~ent, tc How-vor, it i~ to b- undor~tood th~t lectrodee not pr-viou~ly us-d, and th-r-for- not oxidized c~n b~ pr-oxidiz-d and pocificolly fluorin~ted accordlng to th- m-thode di-clo-od h-r-in Pr-forably, beforo specific~lly fluorinating, the oarbon or carbon ubetrate ia cloan-d by tho st-ps of washing thoroughly in wat-r to r-~ove any oxidant or oth-r r-agont, and then thoroughly dri-d sinco w~tor vapor r-maining in the oxidizod carbon will t-nd to roact with th- sp-cific fluorinating a~ent consuming, and '' ~

~' ,' ' . :
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, . . .
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.'~; ' ~ . ' 1'~81744 henc~ w~tin~ the ~ent until ~11 tho w~ter i~ re~ct~d Drying may be performed in a ~uitabl~ de~sicator or re~ctor in ~n inert ~tmosph~ro at a~out loO~ to about soooc, and more pr~forably~ at ~bout 200~ to ~out 300C Drying may be ~cceler~ted if conductod undor ~cuum.
The c~rbon ie then ~pecific~ly fluorin~t~d with a '~oft fluorinating ~gent which, for purposes of the pre~ent invention 18 lntonded to mean ~ fluorin~-cont~ining compound which will not cauae c~rbon-to-caroon fragmentation, but inste~d will re~ct with o~r~on-oxy~on bond~ with repl~coment of oxy~en by fluorine Gener~lly, auch agents will not react with olefin carbon-to-carbon ~lt~a ln the c~rbon atructure Soft fluorlnatlng agents include compounds of the formula wher-ln R ls fluorlne, alkyl, aryl aralkyl or di~lkylamino Speciflc representative example~ of ~oft fluorinating agent~
~ro ~ulfur tetr~fluorid0, n-propyleulfur trifluoride, de-cylsulfur trifluoride, cyclopentyl~ulfur trifluoride, diethyl-aminosulfur trifluorid-, dimethylaminosulfur trifluorido, phenyl-ulfur trifluorid- Also included, are the ~lkyl - and ~ryl~ulfur trifluoride~ prep~red ~nd deacribed by W A Shepp~rd, J, _~ Cbem Sog e4, ~05e (1962) Specific fluorination with the soft fluorin~ting agent~
form trlfluorocarbon, difluorocarbon and monofluorocarbon bonds from c~rboxyl, c~rbonyl und hydroxyl ~roup~ re~pectively Fluorln~tion i~ conducted to the extent that the carbon or graphite ia atobiliz-d, or ~ubstantially all carbon oxide functlon~lity i~ con~erted to carbon-fluorine bond~ It m~y be lZ81744 c~rried out in ~ suit~le re~ctor u~u~lly ~irat flu~h~d with dry inert g~s, eg~ nitrogen If, for inst~nce, ~ulfur tetr~-fluoride ia u~ed, the re~ctor or pre~ure ~ss~l i8 u-u~lly cooled with, for example, a bath of dry ice-acetone, ev~cu~ted to ~oout lmm of pre~sure ~nd sulfur totr~fluoride, for ~x~mple, then introduced in exceea After ee~ling the ~eccel it ia w~r~ed gr~du~lly ~nd then he~ted for v~rying lengths of time, up to ~bout 25 to ~bout 500C, ~nd more prefer~bly, from ~bout 100 to ~boùt 250C The r0~ction ti~ y be ~bout 15 minute~ to ~bout 10 d~ya depending on the te~per~ture The re~ction preCcure ~y v~ry from ~bout ~tmospheric to about 500 p-ig Depending on the lnt-nd-d u~- of the s-l-ctlvely fluorlnated c~rbon or c~rbon ~ubJtr~t- the ~mount of soft fluorinoting ~gent, eg aulfur tetr~fluoride e~ployed con b- sub~t~nti~lly lesa th~n the ~tl~ted qulv~lent ne~dsd to conv-rt all c~rbon "oxlde"
functlon~llty, qulvalent to the c~rbon oxld- function~lity, or up to ~n ~ount which iJ con-id-r~bly ~ore th~n th~t required ~tolohlo~-tric~lly If us-d in exo-~J, ulfur totr~fluoride, for , Y~ple, ~y be proaent in up to ~bout 100 fold by weight or ~ore ~ o that ~ount ~ctu~lly r-qulr-d ; ~ Othor oft fluorin~ting ~-nt- liko ~eleniu~ t-tr~fluorid-1, di-thyl~no-ulfur t-tr~fluQrid- ~nd ~lkyl - or ~ryl~ulfur tetr~fluorid-- and the lik-, s- w-ll a- ~lxtur-~ of th~ ay b-conv-nl-ntly u-~d ln ~n ln-rt olv-nt, uch ~4 ~ethyl-ne chloride, chlorofor~, c~r~on t-tr~chlorido ~nd 1,1 2 trlfluoroerichlorothane Th- fluorinating ~yenta ln such olv-nt- ~y b- ua-d ~t ~t~o-ph-ric pr--sur- or ~bove, ~nd ~t ~ 15 ,,, ; . ,:

-: ' , , ~
~ , .

~8~744 temperatures, u3u~11y from room temper~ture and up to the boillng point of the ~olution. ~ecauee m~ny of these fluorin~ting ~gents ~re liquids at room temper~ture~ ~nd ~bove, they m~y ~l~o be u~ed without a solvent. If a solvent i5 utilized it may be present in ~ny concentr~tion up to ~ l~rge exce e, ~uch th~t tho fluorin~ting ~gent is present in an ~mount from 1 to ~bout 90 percent volume, ~nd more prefor~bly, from ~bout 5 to ~out 75 percent.
Speciic fluorinatlon of the c~rbons may be performed in the presence of a rufficient ~mount of ~ catalyst, either fluorine or non-1uorine cont~ining, Fluorin~ted c4t~1ysts include hydrogen fluorlde, boron trlfluoride, arsenic trifluoride, sodium and pot4s~ium fluoride~, titanium tetraf1uoride and lead tetr~fluoride. Non-fluorine cont~ining cat~ly~ts include lead oxide, tit~nium oxide, trimethyl and triethyl~mines ~nd pyridine. All such c~t~lystu are u-eful with soft fluorin~ting ogenta~
A~ ~n option~l pretre~tment step, prior to ~pecific~lly fluorin~ting with soft fluorin~ting ~gent, dried oxidi~ed Gsrbons may be treated with a very soft fluorin ting ~gent, much a~
hydrogen fluoride, potassium hydrogen fluoride, pot~s~ium fluoroaulfin~te, thionyl fluoride, cy~nuric fluoride, etc. This optional pr-tre~tment ia u~eful for converting pendunt c~rboxyl groups to acyl f1uoridea, and may be carried out, for example, by p~aaing anhydrous hydrogen fluorids over heated carbon. Tre~tment with HF m~y run for ~ever~l hours until su~stanti~lly ~11 re~ctive c~rboxylic ~cid, olefinic c~rbons ~nd other more highly re~ctive aitea h~ve been p~rti~lly fluorin~ted. One auch method . ~ . . , . . ~ .. ~

1,~8~744 is also de~cribed in ~.S. P~t~nt 3,929.gl8 ~D. T. Nor-hri et ~1) .
As ~ further option~l ~tep, tho specific~lly fluorin~ted c~r~ona m~y br further fluorin~te~ with ~ -moder~t~'- or -h~rd--fluorin~ting agent. Th~t ia, the ~pecifically fluorin~ted c~rbon ~nd c~rbon subatr~tes h~ving up to 20 percent by weight fluorine c~n be post-fluorinated to higher levelfi, ie. 65 percent by weight fluorine, p~rticul~rly in ths c~se of 3morphous type c~rbon~. These post fluorinated specific~lly fluorin~ted c~rbons ~re specially uaeful ~g lubrlc~nta ~nd in Li~CFx batteries.
Post fluorin~tions with -h~rd-- fluorin~tin~ ~ent~ i~
intended to refer to fluorine-cont~ining compound~ which ~re c~p~ble of re~cting nondiscrimin~tively with c~rbon moleculea.
~nd in aome lnatancea even reault in their fragment~tion. They tend to fluorin~te olefinic and ~rom~tic c~rbon-to-c~rbon uns~tur~tion ~ite~, ~dding to the l~yered pl~nes of ~enzene rin~
o the ~rbon molecule. Repreaent~tive ex~mples include F2, ClF, ClF3, BrF3 ~nd MFn wherein M iB cob~lt, ~ntimony, m~ng~neae, cerium or ur~nium ~nd n is ~ numbor corresponding to the hi~hest oxid~tion st~te of M.
The "moderate" fluorin~ting ugent~ ure fluorlne-containing compounds which ~re somewh~t lesa reuctlve ~nd more selective th~n h~rd fluorin~ting ~ents, but ~re c~p~ble of producing reuctions which ~re comp~r~ble to the h~rd fluorin~ting ~ent~, ~nd include ~uch represent~tive exumples ~8 ~F2. SbF
S~F3~SbCls, AsF3, C~F2, KS02F, AsFs, etc.
- After completion of the oxid~tion ~nd ~11 fluorination steps ~'~8~744 the ~pecific~lly fluorin~ted c~rbon, gr~phite or c~r~on subatrate i8 tre~ted to remove ~ny tr~ces of unreacted fluorin~tlng ~genta ~nd byproducts Thi~ may be accomp~l~hed, for ex~mple, by puryin~ the fluorin~ted m~teri~l with ~n inert g~s followed ~y thorough wa~hing in w~ter, ~nd dryin~ under v~cuum ~t 150C and lmm pressure The following speci1c example~ demonstr~te the varioua aspects of this invention however, it is to be under~tood th~t these ex~mples ~re for illustr~ti~o purpose~ only ~nd do not purport to be wholly definitive ~ to conditiona ~nd scope EXAMPLE I
A aample of poroùs c rbon identified ~e PC 5~ from Stackpole Carbon Co , St M~ry-, PA , whlch i~ l~rgely amorphous c~rbon, weighing 17 8g was thoroughly waahed in water and then l-ctroch-mically oxidized in an unseparated electrochemical cell containing 5x aqueoua aulfuric acid ~olution at 2SC The Stackpole c~rbon s~mple s-r~ed afi the anode A c~r~on rod W~8 us-d ~- a c~thode and a satur~ted c~lomel electrode <SCE) w~s pl~c-d near the anodo to monltor ond control the anode potential Tho olution w~o m~netic~lly Jtirred while the s~ple w~s loctrochomic~lly oxidizod by mo~ns of ~ potentiost~t ~t controlled pot-ntlal o ~1 30V v~ SCE measured between the ample and SCE The curront was initially 600mA at a cell voltage of l~V Aft-r 35 minute~ the potential of the anode w~s incre~sed to l2 50V to provlde a curront of about 1 0A at a cell voltage of 22V Aftor pa--~go of 17,200 coulo~b- the re~ction wa~ topped and tho oxidlz-d ampl- w~shed well with distilled w-ter and 8~.744 dried The oxidized s~mple w~el pl3ced in a Monel pre~sure ~ea~el ln ~n efficient fume hood, cooled with dry-ice ~cetone, flu~hed with dry nitroyen, ~nd evacu~ted to lmm wit~ ~ vacuum pump Sulfur tetr~fluoride (~bout 45g) W~8 t ntroduced and the re~ction w~s he}d ~t room temperature at 105 pSi for ~bout 1 hour ~hen the temper~ture of the reactor wa~ r~ised to 150C ~nd held ~t this temper~ture for 24 hours On coolin~ to room te~per~ture, excess re~gont ~nd ~oseous products were vonted into ~ tr~p cont~ining aqueous cauatic The reactor ~nd mildly fluorinated c~rbon was purged s~ver~l times with dry nitro~n The s~ple W~5 romoved, w~hod well with w~ter and dried in a dea~ic~tor over P20s ~n vacuo The weight of the fin~l s~ple w~s 18 29 The ele~ental ~n~ly~ howed the pre~ence of 4 0x fluorlne To demonatr~te the use of these fluorin~ted car`oons in o~tterie-, th- pecifically fluorinated c~rbon w~s pl~ced in ~n ol-ctroch-~ic~l cell cont~ining a counter electrode of lithium ~et~l ~nd ~n ~nhydrous olution of lithiu~ perchlorate ~0 25M> in propylen- c~rbon~te, under ~ h-lium ~tmosphere An open circuit potenti~l oir 3 lV w~- ~-~sured with ~ di~it~l volt~eter A
curr-nt of about 2~A w~s ob~-rved with ~ resist~nce in6erted in the circuit oi' 1000 ohm~
~A~P~
To d-mon~tr~t- tho results of che~ic~l oxid~tion ~nd fluorinotlon, 50g of carbon fibers av~ ble under the d--lgnation ~hornel-50, a tr~de~ark o~ Union Carbide are placed in ~ gla8~ be~ker with 500~1 of ~queous sodiu~ hypochlorite solution C5X>, heatod to 50C and magnetically stirred for 12 :

'1.~8~744 hours The oxidized c~rbon fibers ~re rinsed in w~tor, Sx ~queouc sulfuric ~cid~ w~hed well wi~h ~ter ~nd then thoroughly drled The s~mple la next placed ln a Monel re~ctor ~nd heatod to 200C ~t ~tmoapheric presaure, wbile purging with ~ continuous stre~m of ~nhydrouc hydrogen fluoride for 5 hour~ The re~ctor is then cooled, flu~hed with dry nitrogen, ~nd 100~ of sulfur tetr~fluoride i~ introduc-d, accordlng to the ~ethod of EXAMPLE
I Upon reaction at 200C for 24 hours under preaaure, the re~otor is cooled ~nd excesc re~ent ~nd g~seous products ~ented ~nd re~oved ~8 beore The thoroughly w~shed ~nd dried s~mple is next fluorlnatQd ln the s~e re~ctor, whlch is initl~lly fluahed with dry nitrog-n, by slowly (about lOmlJmin~ passing ~ dilute 1uorin-/nitrogen mixture ~bout lOx by volu~e F2) o~er the ~pl- for 30 ~lnutea During the courae of thla proceaa the r-actor temp-r~tur- risoa to about 250~ ~s ~ re~ult of the xoth-r~ic he~t of r-action The reactor ~nd s~mple ~re next cooled by ~e~n~ of ~ str-o~ of pure nitro~en which ~l~o serves to cl-~n th- c~rbon ~pl- o obsorbed ~a-eous cont~in~nts Fin~lly, the ~pl- i- c~rofully w~ahed 4nd dried Analy~i~
shows that th- fluorin- cont~nt is si~nificantly less in th- ~ild *luorin~tion ~t-p with SF4, but the fluerine content is ubst~ntially incre~--d in th- n-xt step using the dilute fluorln- ~ixture Th- s~pl- ia asily wett-d ~ter che~ical oxidation do~on~tr~tin~ th- hydrophilic n~ture of the c~r~on oxide surf~ce Aft-r fluorlnatlon wlth SF4 and then wlth dllute fluorln-, the ., , .~: - ' . ' -- , '' ''' .:

~Z81.744 ~amples sre di~tlnctly hydrophobic in chsr~cter And wster do~s not subatAnti~lly wet the samples EXAMPLE III
A floodod ~ir cathode avail~ble from Prototech, Newton Highl~nd~, Ma , consi~ting of high surf~ce area carbon and TeflonR fibers ~nd containing 0 5mg~cm2 of plstlnum c~talyat i8 re~oved from a phosphoric acid fu-l cell which h~d been operatin~
~t 195C for 6 montha but h~d f~iled Thi~ electrode ia oboervably hydrophilic and is prepared for specific fluorination by wa-hing thoroughly in distilled w~t-r and drying ~t 100C _n vacuo for 24 hours Upon mild fluorination with aulfur tetr~fluoride, which ia u--d in exce~-, the s-lectively fluorinated gas dlffualon electrode, ls r-moved fro~ the r~actor, waahed well ~it ia ob-ervably hydrophobic~, ~nd returnod to uee in ~ phoephoric ~cid fu~l c-ll E~AMPLE IV
A ga~ diffu-ion lectrodo havin~ C~t~lo~ue No PSN
av~ilabl- fro~ the Prototech Co consistin~ of Vulc~n X~-72 carbon ~lxed with T-flonR fiber, containing 0 5~gJcm2 of platlnu~
cataly-t, on a sllver plated nickel oereen is plac-d in ~ srall test eell A nlckol ol-ctrodo servod aG the counter electrode and the l-ctrolyte io 23x aqueous NaOH oolution at 75C Air is introduc-d to tho ga- sid- of th- gaa diffuaion electrode, and at a current d-nsity of 300 a~pXft2, th- electrode pot-ntial is 0 26V ve H~fH~O ~s a roferenGo Aftor lOQO houre of continuou~
, op-r~tion, th~ ctrode potential is -0 2~V and ~ft-r 20,000 ~1 .

' :

~'~8~744 hours, the eloctrode potenti~ de~r~ded to -O ~lV va Hg/HgO
This irrovercibly flooded gas diffusion electrods is removed from th~ c~ll, so~ked ln di~till~d water to r~mov~ c~ustic, thoroughly dried ~nd ~luorin~ted with SF4 at 150 pai, 150C for 4 day~ Tho eloctrode is w ~h~d with distill~d wat~r ~nd r~ountod in the te~t cell described above At 300 amp/ft2, the electrode potonti~l i~ -0 28V vs H~/HgO ~nd ~ft~r con~inuous opcr~tion for 10,000 houra the el~ctrode potentiuol is -0,29V, thereby ds~on~trating that th~ p~rormanc~ of a floodHd ~ir d~pol~rized cathode can be re~tored utilizin~ the present invention, ~nd mor-over that such a r-stored electrod- is greatly i~prov~d in useul lif~time as compared to th- untroatod ~lectrodo ~XA~g V
~ glas~ l-ctroch-~ic~l cell w~ used, h~vin~ two co~part~ent- s-porated by a ~-diu~ porosity gl~ss frit Anode~
<3am dia~ot-r x lSOmm) con-i-ted of preoxldlzod ~nd ~lldly fluorlnot-d (with SF4) vitr-ous carbon rods, fluorin~ted to l-v-l of ~bout S~ fluorin- by ~l~m-ntal analysis, or untrented rod- w-re u--d a- control- Tho cathod- waa stainlesa tool Th - anod- id- of th- c-ll h~d provi-ion for an argon g~- inl-t ond o ~a- outl-t Tho inl-t ond outl-t were of ~l~os tubing with th- inl-t xt-ndin~ b-low th- surfac- of the anolyt- olution ~lOOml~, oon~i~ting of ith-r sulfuric ~cid or t-tr~fluoroboric acld and th- outl-t dipping into an ozone indicating ~olution -~ ~ consi~ting of 0 2M ~quoous pot~s-ium iodid- (lOOml~ Powor w~c suppli-d to the c-ll by a Gates W Pow-r Supply ~urront was ea-ursd by a aockm~n 310 Multim-t-r The charge WA8 int-grated ~::

~:- ' .
,:' ' ' ', ' . . ,', , .
.
' -: ' ' '' - , : ' '; ' 8'1.744 with ~ M~d~l ~40 ~igit~l ~oulom~t~r from Th~ El~ctro~yntho~is ~e ~ E Amherst, N Y Current efficiency for ozone gener~tion w~s determined by lodometric tltrtlon of the ozone indlcAtlng solution using ct~ndard ~odium thiocul~te solution a~ comp~red to the theoretlcal production of ozone ~ccording to the totMl ch~rge p~s~ed Table 1 compares fluorin~ted vs unfluorin~ted vitreoua c~r~on, ~riou~ ~nolyt~ solutionc, the role of current den~ity, ~nd temper~ture The rorults in T~le 1 demonstr~te th~t the ozon~ current e~ficiency i~ si~nificuntly impro~d ovor th~
untre~ted ~node m~teri~l, when fluorin~ted vitr-ou~ carbon i~
ueed ~s the unode MoreovHr, unfluorinuted ~node~ ~controlo) ~re everely de~r~ded in ~queous H2S04 ~olution, wher-~ fluorin~ted onodes und-r the 4~me conditions aurvive intact, thereby cle~rly de~onatr~tin~ the useful protection ~chi-ved by fluorin~tion aocording to the mothod~ of the pr-sent invention The resulte o indlc~to th~t conc ~queou~ HBF4 ia preferred ~ ~nolyte ~nd thst fflci-nt coollng 1- requlred for optlm~l resulta '~

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~Z~7~4 EXAMPLE VI
T~e fluorin~tion of two different c~rbon black~, C~bot Co Vulcan XC-72, ~nd Andercon ~evelopment ~o Super AX-21 were comp~r~d V~lc~n XG-72 i~ commonly u~d in fu~l c~ll ~lectrodes ~nd h~s ~ ~urf~ce area ~ET) of ~bout 250m2~g Super AX-21 is ~ore ~morphous ln character ~nd h~ ~ very high aurf~ce are~ of about 3500m2~g u~eul in absorbing a variety of toxic oubst~nceo ~nd is al~o distingui~-hed by ~ hi4h w~ter content of ~bout ~5~ by welght Prlor to fluorination each carbon waa thoroughly dried in a de~sicator over P20s at 100C for 48 hours Following the fluorin~tion proc~dure descri~ed in ~ S
P~tent 3,340,081, the dried c~rbon (lOg) was placed in ~ 1 llter Parr Bomb, the ~pp~ratu~ vQcuated, and about lOOg of aulfur t-traflùoride introduced The re~ctor w~s then heated to 150C
~nd wa~ m~intained at th~t tomp-r~ture for 5 5 hour~- On cooling to roo~ temperoture, the excess g~s w~s ~ented, the re~ctor flu-hed everal ti~e- with nitrogeD and the fluorinated oample removed, wa4hod w-ll with wat-r and dried A socond Jet of s~ples (25~ of Vulc~n X~-72 ~nd Super AX-21 were preoxidized to d-velop pot-nti~l sites of inst~bility, by ~gnetlcàlly stlrrlng the earbon ln 1 litor of lM aqu-ous a~onlu~ per-ulfate oolution or ln aqu-ou4 hous-hold bleach ~Sx ~ctiv- chlorine~ for 24 hour- ~t roo~ te~per~ture~ Th- oxidized carbon wa- filt-red, wash-d woll with water and thoroughly dried ln a d-~-icator over P20s at 100C for g8 hours Fluorination of lOg ~plo~ wa- thon conduct-d a~ deacrib-d abovQ
The rosults of T~ble 2 de~onstr~te that preoxid~tion followed by fluorin~tion ~ccording to the ~0thods of the present ~5 '~

~Z8~74A

invention ~r~tly incrense~ the fluorine content, comp~red to fluorin~tion ~lone following the U.S. 3,340,081.
This aignificant incre~e in fluorine content i~ related to the gre~ter level of ~urfsce oxides formed upon preo~id~tion. A
~e~ure of the qu~ntity of so~e surf~ce oxide graups mDy be obt~ined by titratlon with b~se. Table 2 ~hows the resulta of titr~tion with ~queous N~OH, which providee the qu~ntity of strong plus we~ker ~aids. Titr~tion with ~queoue N~H~O~, identifie~ th~ level of ~tron~er ~cids only. Stron~ ~cid~ ~re believed to be c~rboxylic groupa where~a we~ker ~cids are l~r~ely phenolic or enolic in n~ture. Thua th- higher surf~ce oxide levelc ~¢hieved ~y prooxid~tion of c~rbons ~ffordc ~ higher level of Jpecific fluorin~tion o carbons bec~use of the presence of ~ore ~v~ le sites for fluorin~tion with ~ soft fluorin~tin~
ag-nt.

TABLE 2. COMPARISQN QF FLUQRINA3IQN AND SURFAE OXIDATION
XETHQDS OF CARBQNS
VULCAN X__Z2 S_PEB AX-21 A: Fluorinetion Without preoxid~tion 2.5X F 3.0x F
Pr-oxidized with NH~252o8 6.~ F 9,~x F
~b> NaOCl 9.4x F 10.5X F
B. 5urf~c- oxig- Tltr~tion~
,: ------______ Without pr-oxid~tion ~ ~ tN~OH~ aeqJg 0.40 0.2Y

; tNsHC03~, ~eqJg 0.11 0.05 ~, ~ ' ' ` ' .

~81744 Preoxidized carbon (NH4~2S20~
~NaOH~, moq~g 0.69 2.97 tNaHC03~, meqJg 0.15 1.~3 While the invention ha heon described in con~unction with ~peciflc example~ thereof, thi~ i3 lllu~tratlve only.
Accordingly, many alternative~, modification~ and variations will be apparent to person~ ~killed in the art in light of the foregoin~ d~cripti~n ~nd it i~ therefore intended to embrace uch ~ltornative~ and modificatione ~ to fall within tho ~pirit and broad ~cope of the append-d claim~.

~7

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-A method of fluorinating a carbon, which comprises the steps of preoxidizing the carbon, and fluorinating the preoxidized carbon by specific fluorination.

The method of Claim 1 wherein the carbon is a material selected from an amorphous or crystalline carbon.

The method of Claim 2 wherein the amorphous carbon is a carbon black and the carbon black is preoxidized and fluorinated at least to a percent by weight fluorine.

The method of Claim 2 wherein the amorphous carbon is a carbon selected from the group consisting of actilvated carbons, glassy carbons, soot and charcoal, said amorphous carbon being fluorinated with a mild fluorinating agent to a level from about 0.1 to about 20 percent by weight fluorine.

The method of Claim 2 wherein the crystalline carbon comprises a graphitic carbon preoxidized and specifically fluorinated to at least 0.01 percent by weight fluorine.

The method of Claim 1 wherein the carbon is a carbon substrate preoxidized and specifically fluorinated to at least 0.001 percent by weight fluorine.

The method of Claim a wherein the carbon substrate is selected from the group consisting of carbon steel, carbon electrode, structural composite and catalyst support.

The method of Claim 6 wherein the carbon substrate is selected from a battery electrode, fuel cell electrode, bifunctional air electrode and vitreous carbon electrode.

The method of Claim 1 including the step of post-fluorinating the specifically fluorinated carbon with a moderate or hard fluorinating agent.

The method of Claim 9 wherein the post fluorinated carbon has a fluorine content ranging from about 0.5 to about 65 percent by weight.

The method of Claim 10 wherein the post fluorination step is conducted with a material selected from the group consisting of F2, ClF, ClF3, BrF3 and MFn wherein M is cobalt, antimony, manganese, cerium or uranium and n is a number corresponding to the highest oxidation state of M.

The method of Claim 6 including the step of cleaning the preoxidized carbon substrate before specifically fluorinating.

The method of Claim 12 wherein the fluorination step is performed with a soft fluorinating agent of the formula: R-SF3 wherein R is fluorine, alkyl, aryl, aralkyl or dialkylamino.

The method of Claim 12 wherein the soft fluorinating agent is sulfur tetrafluoride.

A method of regenerating an oxidized or flooded carbon-containing electrode, which comprises the steps of cleaning the electrode, and specifically fluorinating the cleaned electrode.

The method of Claim is wherein the oxidized or flooded electrode is selected from fuel cell electrodes and bifunctional air electrodes.

A method for extending the useful life of a vitreous or glassy carbon electrodes which comprises the steps of preoxidizing the electrode and fluorinating the preoxidized electrode by specific fluorination.

The method of Claim 17 wherein the electrode is a glassy carbon anode for use in corrosive electrolytes.

The method of Claim 17 wherein the electrode is a glassy carbon anode for the electrochemical generation of ozone.

The method of Claim 17 wherein the electrode is a glassy carbon anode for the electrochemical generation of an inorganic persulfate.

A method of fluorinating a carbon, which comprises the steps of preoxidizing the carbon, cleaning the preoxidized carbon, and specifically fluorinating the preoxidized and cleaned carbon in the presence of a catalyzing amount of HF, BF3 or a metal fluoride salt.

The method of Claim 21, including the step of post-fluorinating the specifically fluorinated carbon with a moderate or hard fluorinating agent.

A preoxidized, specifically fluorinated carbon or carbon substrate having a fluorine content of at least 8 percent by weight fluorine.

The preoxidized, specifically fluorinated carbon or carbon substrate of Claim 24 wherein the carbon or carbon substrate comprises an amorphous type carbon A specifically fluorinated carbon or carbon substrate post fluorinated with a moderate or hard fluorinating agent.

A preoxidized, specifically fluorinated carbon or carbon substrate comprising a carbon selected from the group consisting of activated carbon, glassy carbon, soot and charcoal.

The preoxidized, specifically fluorinated carbon of Claim 26 wherein the carbon is in the form of a powder, cloth, felt or fiber.

A preoxidized, specifically fluorinated carbon or carbon substrate post fluorinated with a moderate or hard fluorinating agent.

A preoxidized. specifically fluorinated crystalline carbon or carbon substrate comprising a crystalline carbon.

The preoxidized, specifically fluorinated crystalline carbon or substrate of Claim 29 which is post fluorinated.

A specifically fluorinated crystalline carbon or carbon substrate comprising a crystalline carbon.

The specifically fluorinated crystalline carbon or carbon substrate of Claim 31 wherein the crystalline carbon is in the form of graphite cloth, felt or fiber.

A carbon which comprises a specifically fluorinated vitreous or glassy carbon.

An electrode which comprises a specifically fluorinated carbon.

The electrode of Claim 34 wherein the specifically fluorinated carbon comprises an amorphous carbon.

The electrode of Claim 35 wherein the specifically fluorinated amorphous carbon comprises a carbon black.

The electrode of Claim 35 wherein the specifically fluorinated amorphous carbon comprises a glassy carbon.

The electrode of Claim 34 wherein the specifically fluorinated amorphous carbon comprises a crystalline carbon.

The electrode of Claim 38 wherein the specifically fluorinated crystalline carbon comprises a graphitic carbon.

The specifically fluorinated carbon electrode of Claim 34 which is a battery electrode.

The specifically fluorinated amorphous carbon electrode of Claim 35 which is a battery electrode.

The specifically fluorinated carbon black electrode of Claim 36 which is a battery electrode.

The specifically fluorinated graphitic carbon electrode of Claim 39 which is a battery electrode.

A battery comprising the electrode of Claim 40 A battery comprising the electrode of Claim 41.

A battery comprising the electrode of Claim 42.

A battery comprising the electrode of Claim 43.

The battery of Claim 44 which includes an electrode comprising lithium.

The battery of Claim 45 which includes an electrode comprising lithium.

The battery of Claim 46 which includes an electrode comprising lithium.

The battery of Claim 47 which includes an electrode comprising lithium.

An electrode which comprises a preoxidized, specifically fluorinated carbon.

The electrode of Claim 52 wherein the preoxidized, specifically fluorinated carbon comprises an amorphous carbon.

The electrode of Claim 52 wherein the preoxidized specifically fluorinated amorphous carbon comprises carbon black.

A battery comprising the electrode of Claim 52.

A battery comprising the electrode of Claim 53.

The battery of Claim 55 including an electrode comprising lithium.

An electrode which comprises the specifically fluorinated and post fluorinated carbon of Claim 25.

A battery comprising the electrode of Claim 58 and an electrode comprising lithium.

An electrode which comprises the preoxidized, specifically fluorinated and post fluorinated carbon of Claim 28.

A battery comprising the electrode of Claim 60 and an electrode comprising lithium.