化学还原氧化石墨烯制备高性能石墨烯自组装水凝胶_英文_

2 Experi m ental
2 . 1 Preparation of GO GO w as prepared by ox id ation o f na tura l g raphite pow der ( 325 m esh , Q in gdao ) acco rding to a m odi [ 13, 37 ] f ie d H umm ers. m ethod . B rief ly, g raph ite power w a s f irst o x id ized using NaNO 3 and KM nO 4 in sul
Foundation item: N ation al N atura l Science Foundation o f Ch in a ( 20774056, 50873052) . Corresponding author : SH I G ao-quan. E -m ai: l g sh@ i tsinghua. edu . cn Author introduction : SHEN G K ai xuan ( 1985- ) , m a le, cand idate fo r Ph . D. , engaged in th e research o f com posite m ateria ls based on graphem e. E -m ai: l sh engkx08@ m a ils . tsinghua. edu . cn Eng lish ed ition avai lab le on lin e ScienceD irect ( http : P P w ww. scienced irec.t com P scienceP journalP 18725805 ) . DO I : 10. 1016 / S1872 -5805( 11 ) 60062 -0
第 26 卷 第 1 期 2011 年 2 月 Artic le ID: 1007-8827( 2011) 01 -0009-07
新 型 炭 材 料 NEW CARBON MATER I AL S
V o.l 26 N o . 1 F eb. 2011
H igh -perfor m ance self -assembled graphene hydrogels prepared by che m ical reduction of graphene oxide
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furic acid. H 2 O 2 w as th en added un til gas evo lution ceased , fo llow ed by the additio n o f exce ss de ion ized w ater . T he react io n m ix ture w as then f iltered and w ashed w ith 1B10 HC l aqueous so lu t io n and th en w ith de io n ized w ater . T he f iltrate cake w as disso lved in de io n ized w ater and d ia lyzed for a t least one w eek to rem ove the rem aining acid and m eta l spec ies , and fi - 1 nally centr ifugated at 4 000 r # m in for 30m in to re m o ve resid ua l graphite . T he as -prepared GO can fo r m stable aqueous d ispersio n by ultrason icat io n due to its strong hydrophilicity. T he thickness o f a GO sheet w as m easured to be about 0 . 8n m, w h ich is in consis tent w ith the va lu es repo rted in literature [ 38] . 2 . 2 P reparation of SGH s T he fo llow ing is the typ ica l prepara tio n proce dure s o f SGH s . 6 m L GO aqueous dispersion -1 ( 2m g#m L ) w a s loaded in a 15 m L g lass v ia . l T hen, 24m g sod ium asco rba te ( Sinophar m Chem ical R eagent C o. , Shanghai) w as added . A f ter sonication fo r 5m in to disso lve the sod iu m asco rbate , a hom o ge neous y ellow-brow n dispersio n w as obta in ed . Succes siv ely, the a s -prepared d ispersion w a s hea ted at 90 e fo r 1 . 5 h to produce th e SGH. T he excess sodiu m ascorbate w as further rem ov ed by dia ly sis . 2 . 3 Characterization s T he hydrog els w ere freeze -drie d and sputtered w ith a 10 nm go ld coa tin g fo r scann in g electron m i cro scopy ( SEM ) characterization . SEM w a s recorded on a S irion 200 f ie ld-e m issio n scann in g electron m i cro scope . T he e lectrica l conduct iv ities o f SGH s w ere m easured by tw o-probe m ethod . A cy lindrica l SGH w as sandw iched betw een t w o p la tin u m fo ils and con nected to a CH I440 po tent io stat g alvanostat ( CH In stru m ents Inc . ) for conduc tiv ity m easure m en ts . D ynam ic frequency exper i m en ts w ere perform ed on a Rheom etrics A res rheom eter w ith 25mm d iam e ter para lle l p late geom etry at 25 e . T he gap d istance betw een tw o p lates w as f ixed to be 1mm. F requency sw eep m easurem ents w ere perform ed in th e rang e - 1 f rom 1 to 100 rad # s at a f ix ed oscillato ry stra in o f 0 . 2 %. T he X-ray d iff ractio n ( XRD ) pa tterns o f f reezedried SGH, GO, and natura l g raphite w ere obtained by usin g a D8 A dvance ( B ruker) X- ray d iff ractom e ter w ith C u K A radiation ( K= 0 . 154 18 nm ) . X-ray pho toe lectron spectro scopy ( XPS) ana ly sis o f freeze dried SGH and GO w as perfo r m ed on a ESCALAB 250 pho toe le ctron spectrom e ter ( T her m oF isher Scien t if ic , U SA ) w ith A l K A ( 1 486 . 6 eV ) as th e X-ray source . E lectro chem ica l experi m ents w ere carried out - 1 usin g a three -e le ctrode sy stem in 1m o # l L aqueous
1
Introduction
G raphene , a tw o-d i m ensiona l ( 2D ) one-atom th ick carbon, ha s attracted in creasing atten tio n in the past severa l y ears , m a in ly due to its o utstanding e le c [ 1-7] tronic , therm a , l and m echanica l properties . F ur ther m o re , graphene has po tent ia l app lic ations in v ari [ 1, 8 - 10 ] [ 11 -13 ] ous f ie ld s such as electron ics , com po sites , [ 14 ] [ 15-17] senso rs , cataly sis , and energy conversion and [ 18-20] sto rage . O n the o ther hand , self-assem bly is an ef fect iv e strategy fo r fabricat ing g raphene -based m ateria ls w ith h ierarchical structures and no vel properties . T ill date, various se lf-assem b ly strateg ie s such as f low-direct [ 21-22] [ 23 ] ed o r evaporat io n - induced se lf-assem b ly , [ 24] L angm uir -B lo dgett technique , and layer -by- la yer [ 25] depo sition have been dev eloped for 2D se lf-assemb ly o f func tio nalized graphene to produce g raphene th in f il ms . Recen tly, w e have dem onstrated that self assem b led g raphene hydrog els ( SGH s) w ith three -di m ensiona l ( 3D ) ne tw o rk cou ld be facilely prepared by a one-step hydro th er m al reductio n o f aqueous g ra phene o x id e ( GO ) dispersio n. T he resu lting g raphene hydro ge ls are e lectrica lly conductive , ther m a lly sta [ 26] [ 27] b le , and m echan ica lly strong . W ang et a . l re ported 3D se lf-assem b ly o f sing le GO sheets assisted by noble m e tal nanopart icles , and they a lso repo rted th at th e com po site m acro structures show ed h ig h ca ta Received date : 2010-12-06 ; R ev ised date: 2011 -02-08
ly tic act iv ity. T he h igh te m perature hydro therm a l m e th od w as tested to be a facile and contro lla ble tech nique fo r 3D assem b ling o f reduced GO shee ts . N ev erthe less , th ism ethod is li m ited by equipm en ts and is relat iv e ly ti m e-consum ing and needs high tem pera ture . T herefo re , a m o re m ild and / green 0 m ethod is needed fo r produc ing SGH s in large scale. In o ur prev ious w o rk , w e revea led tha t the re duction of GO upon hydro ther m a l react io n is th e key step for 3D se lf-assem bly o f reduced GO sheets . Fur [ 28-30] ther m o re , GO can a lso be reduced by che m ica l [ 31-33] and e le ctro chem ica l appro aches o r by therm a l [ 34-36] treatm ents . O n the basis o f this consid eration , w e prepared high -perfo r m ance 3D SGH s by chem ica l reduction o f the aqueous GO dispersio n w ith sod ium asco rbate. T he structure and properties o f th e SGH s prepared by chem ical reduction are si m ilar to th o se o f the SGH s produced by hydro th er m al reactio n. Fur ther m o re , the pure SGH s exhibited a high spec if ic ca - 1 pac itance of 240F# g .
SHENG K ai xuan , XU Y u -x , i L I C hun , S H I G ao-quan
100084, Ch ina ) (D epartm en t of Chem istry, T sing hua Un iv ersity, B eijing
Abstrac t : T hree -di m en sional self-asse m b led graphene hydrog els ( SGH s) have been fabr ica ted by chem ica l reductio n o f g raphene ox ide ( GO ) w ith sod ium asco rbate . T he SGH s w ere character ized by scann ing e lectron m icro sco py, rheo log ica l tests , electrica l conductiv ity m easure m ents , X-ray pho toe lectron spectro sco py, X-ray d iffrac tion, and R am an spec tro scopy . R esults ind ica te that the reduc tion o f GO prom o te s the assem bly o f g raphene sheets . T he SGH s are e lectri - 1 - 1 ca lly conductiv e ( 1 S # m ) and m echanically strong and exhibit exce llent e lec tro che m ica l perfo r m ance . In 1m o# l L aqueous so lution o f H 2 SO 4, the spec ific capacitance o f SGH s w asm easured to be abo ut 240F # g- 1 a t a discharg e curren t density o f 1. 2A# g- 1 . K eywords : Se lf -a sse m b ly; G raphene ; C hem ica l reduction; H ydro ge ls ; Supercapac itor CLC nu m ber : TQ 127. 1+ 1 Docu m ent code : A