(789724120) CNT and Energy Storage

8/16/2019 (789724120) CNT and Energy Storage

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Carbon 43 (2005) 2209–2214 www.elsevier.com/locate/carbon

Hydroen adsor!tion in di erent carbonff nanostr"ct"res#arbara $anella a%&% 'icael Hirscer a% iemar *ot b

a Max-Planck-Institut fu¨ r Metallforschung, Heisenbergstr. 3, D-705!"tuttgart, #er$an%b

Max-Planck-Institut fu¨ r &estk o¨ r'erforschung, Heisenbergstr. (, D-705!"tuttgart, #er$an%

*eceived 23 +"ly 2004, acce!ted 29 'arc 2005-vailable online 10 'ay 2005

)bstract

Hydroen adsor!tion in di erentff carbonaceo"s materials wit o!timied str"ct"re was investiated at room tem!erat"re and 0. -ctivated carbon% amor!o"s carbon nanot"bes% Cs and !oro"s carbon sam!les all sow te same adsor!tion !ro!4erties. e ast 6inetics and com!lete reversibility o5 te !rocess indicate tat te interaction between ydroen molec"les and te

carbon nanostr"ct"re is d"e to !ysisor!tion. -t 0 te adsor!tion isoterm o5 all sam!les can be e7!lained wit te 8anm"irmodel% wile at room tem!erat"re te storae ca!acity is a linear 5"nction o5 te !ress"re. e s"race area and !ore sie o5 tecarbon materials were caracteried by 2 adsor!tion at 0 and correlated to teir ydroen storae ca!acity. - linear relationbetween ydroen "!ta6e and s!eci cfi s"race area (-) is obtained or all sam!les inde!endent o5 te nat"re o5 te carbon material. e best material wit a - o5 250m2/ sows a storae ca!acity o5 4.5 wt: at 0. *005 +lseier t. )ll rights resere.

/e%ors1 -ctivated carbon, Carbon nanot"bes, adsor!tion, -dsor!tion !ro!erties, "race area

(. Intr ouction

Hydroen storae is te bottlenec6 5or te brea6tro" o5 ydroen as enery carrier in a"tomotivea!!lications. ;n te last years di erentff storae tecnoloies ave been investiated


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**( 2. Panella et al. 4arbon 3 6*005 **0!8**(2. Panella et al. 4arbon 3 6*005 **0!8**( **(

able 1Carbon nanomaterials investiated 5or ydroen storae and teir str"ct"ral !ro!erties

am!le (co"ntry) #? - -verae !ore $ore vol"me 5or !ores wit Heli"m density


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**( 2. Panella et al. 4arbon 3 6*005 **0!8**(2. Panella et al. 4arbon 3 6*005 **0!8**( **("ilibri"m is reaced% te as is !er mittedto e7!and in te sam!le older. e meas"red !ress"redro! is ca"sed by te as e7!ansion in a bier


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H2 He

Manometer

reservoir

waterbath

Sample holder

Pump

P

ater eac adsor!tion te sam!le is eated and deassed. is means tat eac storae val"e is obtained inde!endently rom te !revio"s ste!. e corrected ideal ase>"ation wit a com!ressibility actor "! to te secondorder is "sed to calc"late te amo"nt o adsorbed ydro4en 5rom te !ress"re dro!. Jor some sam!les teydroen storae ca!acity in te !ress"re rane 5rom0.2 bar to 0.9 bar and at 0 is meas"red ravimetrically wit a Can microbalance. Here te mass cane asa "nction o5 ydroen !ress"re is recorded. e con4

tecni>"es is a "rter !roo or te acc"racy o5 o"r vol4"metric meas"rin system.

Ji. 1. cematic diaram o5 te ieverts a!!arat"s "sed to meas"reydroen storae in carbon sam!les% Jor meas"rements at roomtem!erat"re reservoir and sam!le older are immersed in te waterbat. Jor meas"rements at 0 te sam!le older is immersed inli>"id nitroen.

vol"me and ydroen adsor!tion in te sam!le. -5terno more !ress"re cane is observed% we wait 5or anadditional 10–15 min to be s"re tat te termal e>"ilib4ri"m is reaced. -ter ydroen adsor!tion at roomtem!erat"re% te sam!le older is cooled in li>"id nitro4en "ntil te new e>"ilibri"m condition is reaced. ;ntis case te decrease o5 te ydroen !ress"re is d"eto te coolin o5 te as and d"e to te enancement o5 adsor!tion in te sam!le at low tem!erat"re. o eval4 "atete storae ca!acity o5 te carbon materials tee7!eriment is re!eated "nder te same conditions wit anonadsorbin blind sam!le (easand) avin te samevol"me as te carbon material. e vol"me o5 tesam!le is meas"red vol"metrically wit eli"m as.

?ac adsor!tion cycle is re!eated at di erentff ydroen !ress"res rom 2 bar to a!!ro7imately 0bar and

3. :esults an iscussion

imilar adsor!tion isoterms ave been obtained 5orall investiated carbon nanostr"ct"res. J"rtermore%tey sow a com!lete reversibility o5 te ydroen "!4ta6e. -5ter eac adsor!tion cycle at a iven !ress"re teydroen is removed rom te sam!le and te meas"rement is re!eated or a di erentff !ress"re. e ydro4en storae ca!acity is inde!endent o5 te n"mber o5 adsor!tion cycles wic !roves tat ydroen is storedreversibly in tese carbon materials. ;5 ydroen as wase7!anded in te sam!le older% te e>"ilibri"m !ress"reis reaced witin a ew seconds. K"rin waitin 5or 10–15min no "rter !ress"re cane is observed% indicatintat termal e>"ilibri"m is reaced. ese ast 6ineticsare caracteristic 5or !ysisor!tion.

Ji. 2 sows te ydroen adsor!tion isoterms o5 activated carbon ; and o5 !"ri edfi Cs ;; at 0and at room tem!erat"re. ?ven to" te two materi4 als!ossess a com!letely di erent nff anostr"ct"re% te sa!eo5 te isoterms is very similar. is sa!e is

Ji. 2. Hydroen adsor!tion isoterms at room tem!erat"re and at 0 ttedfi wit a Henry ty!e and a 8anm"ir ty!e e>"ation% res!ectively (a) 5or activatedcarbon% (b) 5or !"ri edfi Cs.


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caracteristic 5or all investiated carbon materials. -t29B 0 te ydroen "!ta6e is a linear 5"nction o5 te!ress"re% wic can be e7!lained wit Henry s law. -troom tem!erat"re no sat"ration occ"rs in te investiated !ress"re rane and te adsorbed ydroen layeron te carbon s"race is very dil"ted.

-t low tem!erat"re te isoterms can be ttedfi wit a

8anm"irty!e e>"ation (ty!e ; isoterm) indicatintat sat"ration ta6es !lace wit a ydroen monolayerormation% as "s"al 5or micro!oro"s s"races. ;n act%te !ore dimensions limit te ydroen adsor!tion toone molec"lar layer in str"ct"res wit micro!ores"ation "ire more tan ten times ier ental!y o5 adsor!tion "id ydroen. e meas"red val"e corres!onds to an occ"!ancy o5 one ydro4en molec"le !er 1.5 -˚ 2 o5 carbon s"race. -ss"min aclosely !ac6ed distrib"tion o5 ydroen molec"les on

te s"race o5 te adsorbent% tis occ"!ancy corre4s!onds to a retic"lar distance o 4.5 -˚ between ydroenmolec"les on te carbon s"race. J"rter considerinte area o5 a carbon e7aon o5 te ra!ene seet (5.2 -˚ 2)% a!!ro7imately si7 ydroen molec"les wo"ldocc"!y te area o5 20carbon e7aons.

Ln te oter and% "nder te ass"m!tion tat te

closely !ac6ed ydroen monolayer as an intermolec" lardistance e>"al to tat o5 li>"id ydroen (4.1 -˚ )% tee7!erimental val"e at 0 corres!onds to a s"racecoverae o5 B4:.imilar res"lts o5 a linear relation between ydroen"!ta6e and s!eci cfi s"race area o5 carbon materialsave been obtained by iE6am! et al. "idadsorbate. imilar low ydroen storae ca!acities at

k@


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Ji. 4. Correlation between te ydroen storae ca!acity at 0 and te!ore vol"me 5or !ores wit diameter F1.3 nm.

Ji. 5. Hydroen storae ca!acity in wt: at 29B 0 and bar as a5"nction o5 te s"race area o5 te carbon sam!les.

* ave been 5o"nd by '* investiations inCs "ence!romisin materials 5or ydroen adsor!tion arenanostr"ct"res wit i s"race area and micro!oredensity.ile at room tem!erat"re te iest meas"redstorae val"e is less tan 1 wt: even at i ydroen!ress"re% at 0 it is !ossible to store "! to 4.5 wt: o5 ydroen. -mon all investiated materials activatedcarbon wit i rade o5 !orosity is te best carbonnanostr"ct"re 5or ydroen adsor!tion. Lwin to te astadsor!tion and desor!tion 6inetics and te rever sibility%!ysisor!tion is a very !romisin conce!t 5or ydroenstorae at moderate conditions. J"t"re inves tiationsso"ld concentrate on new materials wit s"r ace area%even ier tan activated carbon% in order to acieves"ccess"l storae ca!acities not only at lowtem!erat"re b"t also at ambient conditions.

)cknoleg$ents

e a"tors are tan6"l to *icard Caine 5romte niversiteO d" P"ebec% Canada% 5or te syntesis o5 te activated carbon sam!le ;% +on IaEo 5rom H*88aboratories% Cali5ornia% 5or !"ri5yin te C2;Cs and Cannin -n 5rom Calec% Cali5ornia%5or !rovidin "s wit te sam!les. e are also rate5"l to'a"ricio errones% H"mberto errones% ?d"ardo erres and +ose 'an"el Komin"e 5rom ;$;Cy% 'e74ico% 5or te syntesis o5 te !oro"s carbon sam!les andrs"la Kettlaff elis6ows6a 5rom te 'a74$lanc64;nstit"t 5 "Q r Jest6oQ r!erorsc"n in t"ttart 5or te!"ri cationfi o5 te Cs sam!le ;. L"r tan6 oesalso to -le7ander L6otr"! and 8y"bov #"lseva 5romte ;nstit"te o5 ;noranic Cemistry # *-% *"ssia% 5orte Cs sam!le% to . Hescel rom te 3#era6ademie Jreiber% Germany% 5or !rovidin teactivated Carbon ;; sam!le% to 'aria Meno!ontos;oanno" 5rom *osseter Holdins 8td% Cy!r"s% 5or te*os1 and *os3 sam!les% and to Ronnin 8i" 5romte Ke!artment o5 'aterial cience and ?nineerin atte Mi an +iaton niversity% Cina 5or te amor4!o"s C sam!le. e are also tan65"l to -nnetteJ"cs 5or te 2 sor!tion meas"rements.

:ef erences


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(789724120) CNT and Energy Storage