J Nnostrut 7(4): 292-38, utumn 217 RESERCH PPER Enhned Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts for Ethnol Eletrooxidtion in Fuel Cells Mehri-Sddt Ekrmi-Kkhki 1 *, Jill Sffri 2, Nhid Frzneh 1 nd Sedigheh si 1 1 Nno Tehnology Lortory, Engineering Deprtment, Esfryen University of Tehnology, Esfryen, Irn 2 Young Reserhers nd elite lu, Zhedn Brnh, Islmi zd University, Zhedn, Irn RTICLE INFO rtile History: Reeived 3 ugust 217 epted 12 Septemer 217 Pulished 1 Otoer 217 Keywords: Bimetlli Chitosn Ethnol Eletrooxidtion Fuel Cell Nnoprtiles BSTRCT Here, metl nnoprtiles were synthesized y hemil redution of the orresponding metl slts in the presene of hitosn polymer. Binry nd ternry metlli-hitosn Pt-Fe-CH, Pt-Co-CH nd Pt-Fe-Co-CH nnoomposites were prepred. Trnsmission eletron mirosopy imges nd UV Vis spetr of the nnoomposites onfirmed the presene of the metl nnoprtiles. The eletrotlyti tivity of the nnoomposites for ethnol oxidtion ws tested y yli voltmmetry, Liner Sweep Voltmmetry, mperometri i-t urve nd eletrohemil impedne spetrosopy tehniques. The effet of some experimentl ftors on ethnol oxidtion ws investigted. CO stripping ws used to determine the CO tolerne of the tlysts for ethnol oxidtion. Inorportion of smll mounts of Co nd Fe nnoprtiles in the Pt-CH tlyst used the higher tivity of the tlyst for ethnol eletrooxidtion. The tivtion energy of Pt-Co-Fe-CH tlyst otined from the rrhenius eqution ws lower thn other studied tlysts. These results showed tht Pt-Fe-Co- CH tlyst hs etter tlyti tivity for ethnol oxidtion mong ll prepred tlysts. How to ite this rtile Ekrmi-Kkhki M. S, Sffri J, Frzneh N, si S. Enhned Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts for Ethnol Eletrooxidtion in Fuel Cells. J Nnostrut, 217; 7(4):292-38. INTRODUCTION In reent yers, muh ttention hs een pid to diret lohol fuel ell (DFC), euse diret-fed liquid fuel ell is idel for portle pplitions due to its ompt system nd high energy density fuel storge [1-3]. However, the rel ommeriliztion of DFCs is still hindered y signifint energy loss. The mjor losses re used y the poor tivity of the oxidtion of methnol s the simplest lohol nd its rossover from the node to the thode tht leds deresed thode potentil [4]. So to develop n pproprite fuel for DFC, some orgni fuels suh s oxidtion of ethnol [5], dimethoxymethne [6], formi id [7], propne [8] nd ethylene glyol [9] hve een studied. However, these fuels still hve some prolems regrding their eletrohemil tivity, energy * Corresponding uthor Emil: ekrmi@esfryen..ir density nd rossover prolem. Oxidtion of ethnol is more diffiult thn tht of methnol with the neessity of reking the C C ond for omplete oxidtion. Inresing the eletrotivity of ethnol nd its omplete oxidtion is ruil tsk nd is hrd hllenge [1]. It is reported tht ethnol is oxidized to etldehyde nd CO 2 y dul-pth mehnism in whih the oxidtion to etldehyde nd CO 2 ws ourred y the dehydrogention of dsored ethnol nd dsored intermedites, respetively [11]. The omplexity of this retion nd the presene of so mny intermedites require the development of novel node tlysts, le to rek the C C ond, to relese 12 eletrons nd to ompletely oxidize the poisoning speies t lower over potentils [12]. CO n e esily removed y inorporting This work is liensed under the Cretive Commons ttriution 4. Interntionl Liense. To view opy of this liense, visit http://retiveommons.org/lienses/y/4./.
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts of trnsition metl into the Pt tlyst, ut this improvement requires ost nd stility. In order to design new tlysts, the properties of Pt nd Pt-ontining systems needs to e superior understood [13]. Reent reserh on the oxidtion of ethnol is entered on the development of pproprited tlysts. PtMnCuX (X= Fe, Co, Ni nd Sn) nd PtMnMoX/C (X= Fe, Co, Ni, Cu nd Sn) hve een studied s suitle mterils [14]. Severl polymers re very onvenient supports for dispersing tlyti mterils t the moleulr level in suh wy tht eh tlyti enter will e essile to the retive moleules. Chitosn (CH) offers gret dvntges due to its non-toxiity nd suitle dhesion to the eletrode sustrte [15]. The ddition of hitosn into nole metl ontining tlysts n signifintly improve the eletrode performne for lohol oxidtion. In the present work, very simple method ws used for preprtion of Pt nd Pt-sed tlysts in the presene of hitosn s the support. Initilly, we investigted the tlyti oxidtion of ethnol on pltinum nnoprtiles (NPs) dispersed into hitosn (PtNPs-CH). In order to improve the tlyti tivity of Pt, we prepred inry nd ternry tlysts dispersed in hitosn, PtNPs-M-CH (M=Co, Fe) nd PtNPs-CoNPs-FeNPs- CH for eletrooxidtion of ethnol. To prepre nnoomposites, suitle metl ions were redued into zero vlent nnoprtiles in the hitosn solution. The prepred nnoprtiles were hrterized y UV-Vis spetr nd trnsmission eletron mirosopy (TEM). The eletrohemil tivity of PtNPs-CH, PtNPs-M-CH (M = Co, Fe) nd PtNPs-CoNPs-FeNPs-CH nnoomposites towrd ethnol oxidtion (EO) retion were investigted y yli voltmmetry (CV), Liner Sweep Voltmmetry (LSV) nd mperometri i-t urve mesurement (i-t) tehniques. Comprtive studies of the eletrotlyti tivity of the nnoomposites were rried out towrd ethnol oxidtion retion (EOR). Different prmeters ffeting on EO t the prepred tlysts were investigted. The influene of temperture on the eletrohemil properties of the nnoomposites ws lso investigted nd the tivtion energies of EOR were lulted using the rrhenius eqution. MTERIL ND METHODS Preprtion of the nnotlysts PtNPs-CH, PtNPs-FeNPs-CH, PtNPs-CoNPs- CH nd PtNPs-CoNPs-FeNPs-CH tlysts were prepred y hemil redution of the proper metl preursors, H 2 PtCl 6 (Merk), CoCl 2.6H 2 O (Merk) nd FeCl 3.6H 2 O (for nlysis, Merk) with NBH 4 (Merk) s the reduing gent. t first, solution of hitosn ([2-mino-2-deoxy-(1-4)-β-Dgluopyrnose], with medium moleulr weight, 4 D, Fluk) (2 mg/ml) ws prepred in 1% eti id (glil, Merk) solution. Due to the poor soluility of hitosn, the mixture ws stirred to ompletely dissolve nd kept for overnight. The solution ws filtrted through.22 m Millipore syringe filters to remove ny impurity efore use. To ensure the entire redution, the onentrtion of NBH 4 ws 1 times tht of metl slt. In typil proedure, 25 µl metl slts (CoCl 2. 6H 2 O (.4 M), FeCl 3.6H 2 O (.4 M) nd H 2 PtCl 6 (1M) or mixture of metl slts queous solution) ws mixed with 3 ml of hitosn solution, the mixtures were stirred using rotry perture (1 rpm) for 9 min, then freshly prepred queous solutions of NBH 4 (5µl,.4M) were dded to the mixture, nd stirred for nother 3 min until the entire redution of metl slts. Metl hitosn nnoomposites were formed y dsoring of metl nnoprtiles onto the surfe of hitosn moleules. The prepred nnoomposites were kept t room temperture for hrteriztion. The douly distilled wter ws used for preprtion of the queous solutions. Chrteriztion The size, shpe nd dispersion of the nnoprtiles were determined y TEM imges. TEM imges were tken with using Philips CM12 trnsmission eletron mirosope with the resolution ~ 2.5 Å. n nlytikjen SPE-CORD S1 spetrometer with photodiode rry detetor reorded UV-Vis spetr of the nnoomposites. Eletrohemil investigtions The eletrohemil hrteriztions of the PtNPs-CH, PtNPs-FeNPs-CH, PtNPs-CoNPs-CH nd PtNPs-FeNPs-CoNPs-CH tlysts were rried out with potentiostt/glvnostt utol (Nov softwre model PGSTT 32N, Metrohm, Netherlnds) ontrolled y personl omputer in onventionl three-eletrode ell. sturted lomel eletrode (SCE) ws used s the referene eletrode nd pltinum eletrode served s the ounter eletrode. The glssy ron (GC) J Nnostrut 7(4): 292-38, utumn 217 293
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts eletrode with 2 mm of dimeter polished with.5 µm lumin slurry nd oted with thin lyer of the nnoomposites ws served s the working eletrode. Before oting the tlyst lyer, the polished GC eletrode ws sonited in wter nd solute ethnol, lened nd tivted y yli voltmmetry tehnique etween 1.5 nd +1.5 V in freshly prepred deoxygented 1. mol.l 1 H 2. 5 µl of the nnoomposites ws deposited onto n tivted GC eletrode, nd then ws dried under IR rdition for 1 min. The eletrolyte solutions, mde of 3 ml of.5 M H 2 or.5 M H 2 nd 1.7 M C 2 H 5 OH, were purged with N 2 for 3 min prior to eh mesurement. ll the eletrohemil investigtions were done t the sn rte of 1 mv s -1. RESULTS ND DISCUSSION Spetrosopi nd mirosopi nlysis Formtion of the nnoprtiles ws onfirmed y UV Vis spetr nd TEM oservtions. The UV Vis spetrum of pltinum hitosn nnoomposite ws shown in Fig. 1. s seen, the sorption pek of Pt (IV) speies spetrum whih oserved t ~ 265 nm (Fig. 1 ()) [16], disppered ompletely fter the retion. This indited tht Pt (IV) speies used up nd the olloidl Pt nnoprtiles formed (Fig. 1 ()). UV-Vis spetr of olt nd iron hitosn nnoomposites were shown in Fig. 1B. UV-Vis spetrum of CoCl 2 solution ws indited in Fig. 1B (). It is ler tht there is not ny sorption pek for CoCl 2 solution in the rnge of 23-89 nm. Fig. 1B () showed the UV-Vis sorption spetrum of Co nnoprtiles dispersed in hitosn. The sorption pek of the spetrum t 3 nm ws ttriuted to the formtion of Co nnoprtiles [17]. Formtion of iron nnoprtiles ws lso deteted y UV-Vis spetrum (see Fig. 1B ()). sorptions peks of the spetrum were seen t two wvelengths (23 nd 34 nm). The oserved shifts in peks of the nnoprtiles my e due to medi ompositions or prtiles size [18]. UV-Vis spetrum of FeCl 2 solution hs een shown in Fig. 1B (d). TEM imge of Pt nnoprtiles nd their distriution in hitosn ws shown in Fig. 1C. sorne B sorne d 23 32 41 5 59 68 Wvelength / nm 2 31 42 53 64 75 86 Wvelengh / nm Fig. 1. UV Vis sorption spetr of () H2PtCl6 solution, () Pt nnoprtiles, B() CoCl 2 solution, B() Co nnoprtiles, B() Fe nnoprtiles, B(d) FeCl 2 solution dispersed in hitosn, C TEM imge of Pt nnoprtiles nd their distriution in hitosn. 294 J Nnostrut 7(4): 292-38, utumn 217
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts s seen, Pt nnoprtiles were spheril nd nno-size. The overll size of Pt nnoprtiles rnged round 1 to 4 nm with the men size of 2.48 nm. Fig. 2 showed TEM imges of PtNPs- CoNPs, PtNPs-FeNPs nd PtNPs-CoNPs-FeNPs dispersed in hitosn. TEM imge of PtNPs-FeNPs-CH ws shown in Fig. 2. s seen, there ws good dispersion of Pt nd Fe nnoprtiles in hitosn solution. Fig. 2 lerly indited tht the prepred Pt nd Fe nnoprtiles were spheril nd rnged round 2 to 4.5nm with the men size of 3.2 nm. Fig. 2 showed TEM imge of PtNPs-CoNPs dispersed in hitosn. s seen, Pt nd Co nnoprtiles were suessfully synthesized. They were spheril nd there ws very good dispersion of the prepred nnoprtiles in hitosn. The overll size of the nnoprtiles rnged round 1 to 4 nm with the men size of 2.37 nm. TEM imge of PtNPs-CoNPs-FeNPs dispersed in hitosn hs een shown in Fig. 2. s seen, nnoprtiles were spheril nd rnged round Fig. 2. TEM imges of () pltinum-iron, () pltinum-olt nd () pltinum-olt-iron nnoprtiles distriuted in hitosn. J Nnostrut 7(4): 292-38, utumn 217 295
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts 2 to 5 nm with the men size of 3.31 nm. There ws very good dispersion of the nnoprtiles in hitosn. This ws due to the hitosn usge whih llows etter dispersion of nnoprtiles vi lrger portion of the surfe nd thus prevents the gglomertion of the metlli prtiles. Eletrohemil hrteriztion The eletrohemilly tive surfe re (ES) of PtNPs is min prmeter for investigtion of the tlyti tivity, espeilly for n oxidtion retion s surfe nd heterogeneous retion. ES n e lulted through the CV tehnique with the voltmmogrms of H 2 dsorption/ desorption of the modified eletrodes (Fig. 3). The pltinum ES of the modified eletrodes n e lulted with determintion of the olumi hrge (Q H ) for hydrogen dsorption/desorption. Q H is the men vlue etween the mounts of hrge exhnged during the eletrohemilly dsorption (Q H ) nd desorption (Q H ) of H 2 moleules on the Pt sites [19] (Eq. 1). Q H = (Q H +Q" H )/2 (1) It ws lulted y determining the re under the pek t the potentil rng of hydrogen dsorption/desorption on the prepred eletrodes. The ES mount for Pt nnoprtiles ws lulted with Q H nd Eq. (2) [2-22]: ES=Q H /S L (2) S is ftor relting the hrge to re (=.21 mc.m -2 ). This ftor indites the hrge required for oxidtion of H 2 dsored monolyer on the Pt prtiles. L is the Pt loding (mg.m -2 ) tht ws ~.51mg.m -2 for the modified eletrodes. The lulted ES mounts of PtNPs-CH, PtNPs- FeNPs-CH, PtNPs-CoNPs-CH nd PtNPs-CoNPs- FeNPs-CH tlysts with similr Pt loding were 39.78, 5.59, 68.24 nd 148.44, respetively. s oserved, PtNPs-CoNPs-FeNPs-CH nnotlyst hd the highest ES vlue mong other prepred tlysts showing tht this nnotlyst hd the highest tlyti tivity for EO retion. s seen, ES mount of s-prepred nnotlysts were s follows: PtNPs-CH<PtNPs-FeNPs-CH<PtNPs-CoNPs- CH<PtNPs-CoNPs-FeNPs-CH CO stripping voltmmogrms were investigted to get more informtion out the CO oxidtion hrteristis on the tlysts. Fig. 4 (d) showed the dsored CO (CO ds ) stripping voltmmogrms for the PtNPs-CH (Fig. 4), PtNPs-FeNPs-CH (Fig. 4), PtNPs-CoNPs-CH (Fig. 4) nd PtNPs-CoNPs-FeNPs-CH (Fig. 4d) tlysts in.5m H 2. CO ws purged while holding the potentil t.2 V vs. SCE for CO 3 B 3 15-15 1-1 -3-3 -5 -.4.4.8 1.2 -.4.4.8 1.2 C 6 D 7 25-1 -45-8 -.4.4.8 1.2 3-1 -5-9 -.4.4.8 1.2 Fig. 3. CV urves of ) PtNPs-CH, B) PtNPs-FeNPs-CH, C) PtNPs-CoNPs-CH nd D) PtNPs-CoNPs-FeNPs- CH tlysts in.5 M H2SO4. 296 J Nnostrut 7(4): 292-38, utumn 217
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts j /m m -2 B 35 3 25 2 15 1 5-5 -1-15 dsorption. The dsorption time of CO ws set to 2 min. Further inrese in the dsorption time did not hve ny effet on the voltmmogrms. ll stripping voltmmogrms showed single CO oxidtion pek. To remove the dissolved CO, the solution ws purged with N 2 for 3 min efore the stripping test. No CO oxidtion ws determined in the seond sn inditing the omplete removl of the CO ds speies. For the PtNPs-CH tlyst, shrp CO oxidtion pek ppered t.7v nd the onset potentil of CO oxidtion ws.62 V (Fig. 4). s seen in fig. 4, for PtNPs-FeNPs-CH tlyst, the CO oxidtion pek ppered t.64 V 3 25 2 15 1 j /m m -2 35 3 25 2 15 1 5-5 -1-15 35 d d 3 25 2 15 1 5-5 -1-15 -.2.2.4.6.8 1 1.2 1.4 -.2.2.4.6.8 1 1.2 1.4 E/ V vs. SCE E/ V vs. SCE j /m m -2 -.2.2.4.6.8 1 1.2 1.4 E/ V vs. SCE 5-5 J Nnostrut 7(4): 292-38, utumn 217 nd the onset potentil ws.54 V. For the PtNPs- CoNPs-CH tlyst, shrp CO oxidtion pek ppered t.68v nd the onset potentil of CO oxidtion ws.6 V (Fig. 4). s oserved in Fig. 4d, for PtNPs-CoNPs-FeNPs-CH tlyst, the CO oxidtion pek ppered t.59 V nd the onset potentil of CO oxidtion ws.36 V. The potentil of CO oxidtion pek nd lso the onset potentil of CO oxidtion pek for ll s-prepred tlysts were s follows: PtNPs-CoNPs-FeNPs-CH<PtNPs-FeNPs-CH<PtNPs- CoNPs-CH<PtNPs-CH B 3 2.2 B 3 g 2.2 1.7 g 25 f 1.2 1.7 25 e f 2.2 1.2.7 2 g e.7 2 d 1.7.2 15 d.2 f -.3 15 1.2 -.3 e.3.6.9 1.2 1.5 1.7.3.6.9 1.2 1.5 1 5 d.2 5,, -.3,,.3.6.9 1.2 1.5-5 -5.4.8 1.2 1.6.4.8 1.2 1.6,, E / V vs. SCE Fig. 4. ) CO stripping voltmmogrms of ) PtNPs-CH, ) PtNPs-FeNPs-CH, ) PtNPs-CoNPs-CH, d) PtNPs- CoNPs-FeNPs-CH tlysts in.5m H2SO4. B) Cyli voltmmogrms for EO in 1.7 M ethnol nd.5 M H2SO4 t ) GC/CH, ) GC/CoNPs-CH, ) GC/FeNPs-CH, d) GC/PtNPs-CH, e) GC/PtNPs-FeNPs eletrodes, f) GC/PtNPs-CoNPs-CH nd g) GC/PtNPs-CoNPs-FeNPs-CH eletrodes. (CV t GC eletrode is not shown, whih is similr to tht of GC/CH eletrode) (Fig. 4B (), (), nd () re shown in the inset). d.4.8 1.2 1.6 297
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts The negtive shift in the pek potentil nd onset potentil of CO oxidtion pek might show fster hrge trnsfer kinetis of the CO oxidtion proess [23]. The oxidtion pek of CO ds for PtNPs- CoNPs-FeNPs-CH tlyst ws more negtive thn PtNPs-FeNPs-CH, PtNPs-CoNPs-CH nd PtNPs- CH tlysts. This shows tht CO ds oxidtion is energetilly more fvorle t PtNPs-CoNPs- FeNPs-CH tlyst. The lower pek potentil for CO oxidtion t PtNPs-CoNPs-FeNPs-CH tlyst is proly due to the presene of the oxygented speies on Co nd Fe sites t lower potentils ompred to pltinum [24 26]. Ethnol oxidtion retion (EOR) Eletrohemil properties of the modified eletrodes hve een investigted y yli voltmmetry in 1.7 M C 2 H 5 OH nd.5 M H 2 queous solution nd the typil yli voltmmogrms for GC/CH, GC/CoNPs-CH, GC/ FeNPs-CH, GC/PtNPs-CH, GC/PtNPs-CoNPs-CH, GC/PtNPs-FeNPs-CH nd GC/PtNPs-CoNPs-FeNPs- CH nnoomposites were shown in Fig. 4B. No urrent peks of EO n e oserved in the CV urves of the GC nd GC/CH eletrodes (Fig. 4B ()), whih indites tht the GC nd GC/CH sustrte hs no ovious eletrotlyti tivity for EO (CV t GC eletrode ws not shown, whih ws similr to tht of GC/CH eletrode). Cyli voltmmogrms of GC/CoNPs-CH nd GC/FeNPs- CH eletrodes were shown in Fig. 4B () nd 4B (). s n e seen these eletrodes hs no ovious eletrotlyti tivity for EO. Fig. 4B (), 4B () nd 4B () were shown oviously in the inset of Fig. 4B. On the other hnd, the typil yli voltmmogrm for ethnol eletrooxidtion in.5 M H 2 otined with GC/CH eletrode ontining the PtNPs dispersed eletrotlyst (GC/PtNPs-CH) ws presented in the Fig. 4B (d) nd high eletrotlytil tivity ws oserved. The eletrotlyti tivity of the eletrode depends on the portion of the surfe whih ville to prtiipte in the dispersion of metlli prtiles. It hs een reported tht the use of more porous mtrix of ondutive polymers llows etter dispersion of eletrotlyti prtiles through lrger portion of the surfe nd thus prevent gglomertion of metlli prtiles [27]. s seen in Fig. 4B (d), two oxidtion peks for EO n e oserved during the forwrd sn t.785 (J f1 ) nd 1.23 V (J f2 ). The third oxidtion pek of ethnol eletrooxidtion on the GC/PtNPs-CH eletrode ws seen during the kwrd sn t.486 V. s mentioned in the literture [28, 29], three oxidtion peks n e seen for ethnol eletrooxidtion. Two oxidtion peks n e oserved during the forwrd sn. The first oxidtion urrent pek (J f1 ) minly ourred due to the CO 2 formtion. fter the first pek, the urrent density deresed slightly. This hppened due to the oxidtion of the Pt nnoprtiles on the surfe whih deresed the numer of tive sites. In the following, with inresing the potentil, the urrent density inresed gin nd the seond oxidtion pek (J f2 ) ppered. In ft, the EO retion ould our on the Pt oxide surfe t suh high potentil. Formtion of CH 3 CHO used formtion of the seond oxidtion pek (pek J f2 ) [28]. In the kwrd potentil sweep, Pt oxide is redued to pltinum nd produed len PtNPs surfe. In these surfe, ethnol eletrooxidtion ours nd the urrent pek (J ) oserves. In order to investigte the effet of CoNPs nd FeNPs on the eletrotlyti tivity of GC/ PtNPs-CH eletrode, the ontent of Pt ws kept t onstnt vlue (8 mm) nd the onentrtion of metl nnoprtiles ws.33 mm. Fig. 4B (e) displyed the representtive CV of ethnol eletrooxidtion otined on GC/PtNPs-FeNPshitosn eletrode. s seen in Fig. 4B (e), high eletrotlyti tivity ws oserved. The eletrotlyti tivity of PtNPs-FeNPs-CH towrd ethnol eletrooxidtion ws higher thn tht of PtNPs-CH tlyst. Two oxidtion peks for the EO retion n e oserved during the forwrd sn t.793 nd 1.215 V. The third oxidtion pek of EO on GC/PtNPs-FeNPs-hitosn eletrode ws seen during the kwrd sn t.449 V. Fig. 4B (f) showed the eletrooxidtion of ethnol on GC/ PtNPs-CoNPs-hitosn eletrode. s Seen, two oxidtion peks of ethnol eletrooxidtion n e seen during the forwrd sn t.787 V (J f1 ) nd 1.213 V (J f2 ), respetively. The third oxidtion pek ws oserved during the kwrd sn t.485 V (J ). Eletrooxidtion of ethnol on GC/ PtNPs-CoNPs-FeNPs ws shown t Fig. 4B (g). s oserved, two oxidtion peks were seen in the forwrd sn t the potentils of.785 V (J f1 ) nd 1.29 V (J f2 ), respetively nd the third oxidtion pek ws oserved during the kwrd sn t.486 V. The onset potentil of urrent rise t GC/ PtNPs-hitosn, GC/PtNPs/FeNPs-hitosn, GC/ PtNPs-CoNPs-hitosn, GC/PtNPs-CoNPs-FeNPshitosn eletrodes ws.24,.237,.224 nd.2 298 J Nnostrut 7(4): 292-38, utumn 217
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts V, respetively. The onset potentil hnges of s prepred eletrodes were s follows: PtNPs-CoNPs-FeNPs < PtNPs-CoNPs < PtNPs-FeNPs < PtNPs The onset potentil of EO on GC/PtNPs-CoNPs- FeNPs ws less thn other nnotlysts showing tht this tlyst hs etter tlyti tivity towrd ethnol eletrooxidtion. The nodi pek potentil hnges of EO t s-prepred eletrodes were s follows: E f1 : PtNPs-CoNPs-FeNPs = PtNPs < PtNPs-CoNPs < PtNPs-FeNPs E f2 : PtNPs < PtNPs-CoNPs-FeNPs < PtNPs-CoNPs < PtNPs-FeNPs The nodi pek potentils of EO t PtNPs- CoNPs-FeNPs nnotlyst ws less thn PtNPs- CoNPs nd PtNPs-FeNPs tlysts inditing tht this tlyst hs etter tlyti tivity towrd ethnol eletrooxidtion. The first nodi urrent density (J f1 ) of EO t GC/PtNPs-hitosn, GC/ PtNPs-FeNPs-hitosn, GC/PtNPs-CoNPs-hitosn nd GC/PtNPs-CoNPs-FeNPs-hitosn eletrodes ws 11.31, 146.73, 161.75 nd 165.46 m m - 2, respetively nd the seond nodi urrent density (J f2 ) ws 183.71, 224.29, 245.99 nd 275.6 m m -2, respetively. Compred with the pure Pt tlyst, dding ertin mount of Fe nd Co nnoprtiles to the mtrix of Pt nnoomposite n improve its tlyti tivity for the EO retion. Our investigtions showed tht PtNPs-CoNPs- FeNPs nnotlyst hd higher tlyti tivity towrd ethnol eletrooxidtion due to the higher nodi urrent density, lower onset potentil nd lower nodi pek potentils. lso, EO retion ws investigted on GC/CoNPs-CH (4B ()) nd GC/FeNPs-CH (4B ()) eletrodes without ny pltinum. s seen in Fig. 4B () nd 4B (), these eletrodes did not hve ny onsiderle tivity for the EO retion. In order to investigte the EO retion on Ptsed tlysts, knowing the mehnism of CO poisoning in the EO retion seems to e importnt (Eqs. 3-12). The first retion of ethnol with Pt nnoprtiles is dsorption of ethnol on the Pt surfe to give Pt(C 2 H 5 OH), whih requires severl free Pt inding sites. Then, dehydrogention of ethnol egins on PtNPs surfe. Pt-(CO) ds (Eq. 8), roneous speies suh s etldehyde (Eqs. 5 nd 6), eti id (Eq. 12) nd methne (Eq. 9) re produed [3]. It is well known tht the J f pek involves the progress of these vrious steps nd depends on the quntity of len tive sites ville on PtNPs surfe. Then, dissoition of wter ours on the pure Pt eletrode nd the produed OH groups remove the dsored CO from the Pt surfe (Eqs. 1 nd 11). The mehnism of EO on the pltinum surfe seems to e s follows: Pt+CH 3 -CH 2 OH Pt-OCH 2 -CH 3 + e + H + (3) Pt + CH 3 -CH 2 OH Pt-CHOH-CH 3 + e + H + (4) Pt-OCH 2 -CH 3 Pt + CHO-CH 3 + e + H + (5) Pt-CHOH-CH 3 Pt + CHO-CH 3 + e + H + (6) Pt + CHO-CH 3 Pt-CO-CH 3 + e + H + (7) Pt-CO-CH 3 + Pt Pt-CO + Pt-CH 3 (8) Pt-CH 3 + Pt-H 2Pt + CH 4 (9) Pt + H 2 O Pt-OH + e + H + (1) Pt-CO + Pt-OH 2Pt + CO 2 + e + H + (11) CHO-CH 3 + Pt-OH Pt + CH 3 -COOH + e + H + (12) Eletrohemil impedne spetrosopy (EIS) for ethnol eletrooxidtion In the eletrohemil impedne spetrosopy (EIS) investigtions, the eletrohemil performne of the working eletrodes n e evluted y Nyquist plot [31]. Generlly, there is semiirle prt nd stright line in the Nyquist plot. The semiirle prt in the high frequeny region is due to iruit ontining resistne element prllel to pitne element [32]. The stright line in the low frequeny region orresponds to the Wrug impedne. Usully, the semiirle dimeter equls the hrge trnsfer resistne (R t ). smller mount of the semiirle dimeter nd therefore lower vlue of R t indite the fster hrge trnsfer retion rte. Fig. 5 illustrtes the Nyquist plots of PtNPs- CH, PtNPs-FeNPs-CH, PtNPs-CoNPs-CH nd PtNPs- CoNPs-FeNPs-CH nnotlysts in the solution of J Nnostrut 7(4): 292-38, utumn 217 299
- Z / (KΩ) B If1/I 3 25 2 15 1 5 1.3 1.1.9.7.5.3 M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts.1 3 d.8 3 25.1.6 25 d.4 2.8.2 2.6 15 15.4.2.4.6.8.1 1 d Z / (KΩ 1 d.2 5 5.2.4.6 d Z / (KΩ 3 6 9 12.8.1 3 Z 6/ (KΩ 9 12 Z / (KΩ - Z - Z / (KΩ) / (KΩ) B 1.3 C 1.9 B 1.3 1.1 1.7 1.1 1.5.9.9 1.3.7 Z / (KΩ 1.1.7.5.9.5.3.7 C.3 1.9 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1.7 Cyle numer Cyle numer Cyle numer 1.5 Fig. 5 ) Nyquist plots for ) PtNPs-CH, ) PtNPs-CoNPs-CH, ) PtNPs-FeNPs-CH, d) PtNPs-CoNPs-FeNPs- CH tlysts oted GC eletrode in.5 M H2SO4, 1.7 M C2H5OH queous solution, B) the If1/I rtio nd C) 1.3 If2/I rtio of ) PtNPs-FeNPs, ) PtNPs-CoNPs nd ) PtNPs-CoNPs-FeNPs eletrodes s funtion of the CV yle numer for EO retion. If1/I If1/I 3 6 9 12.5 M H 2 nd 1.7 M ethnol. EIS investigtion ws done t the open iruit potentil (OCP). s seen in Fig 5, ll s prepred tlysts hd very smll semiirle dimeter in the high frequeny region. For PtNPs-CoNPs-FeNPs-CH tlyst, the semiirle dimeter ws smller thn other Cyle numer tlysts. Therefore, the hrge trnsfer proess of EOR ourring on the PtNPs-CoNPs-FeNPs- CH tlyst is so fster thn those on other nnotlysts. 1 2 3 4 5 Durility test of the eletrodes In order to exmine the poisoning effet of s-prepred eletrodes during EO, tlyti tivity of PtNPs-CoNPs-CH, PtNPs-FeNPs-CH nd PtNPs-CoNPs-FeNPs-CH nnoomposites ws investigted through yli voltmmetry nd 5 yles repetedly. The I f1 /I nd I f2 /I rtios of sprepred eletrodes s funtion of yle numer re shown in Fig. 5B nd 5C, respetively. s If2/I - Z / (KΩ) 1.1 If2/I - Z / (KΩ) oserved.9 for PtNPs-FeNPs-CH nnoomposite, I f1 / I nd lso I f2 /I rtios deresed during 5 yles, inditing.7 the poor nti-poisoning performne of this tlyst. For PtNPs-CoNPs-CH, 1 2 there 3ws 4 grdul 5drop of I f1 /I rtio within Cyle the first numer 1 yles, wheres it exhiited n inresing trend fter 1 yles, there ws little derese from 25 to 35 yles nd gin inresed up to 5 yles. lso, for PtNPs-CoNPs- CH, there ws grdul inrese in the I f2 /I rtio during the first 25 yles, it hd little derese from 25 to 35 yles nd then inresed up to 5 yles. For PtNPs-CoNPs-CH tlyst, the mximum mounts of the I f1 /I nd I f2 /I rtios were.83 nd 1.29, respetively. For PtNPs-CoNPs-FeNPs-CH tlyst, the I f1 /I nd I f2 /I rtios deresed during the first 1 yles nd it grdully inresed up to 5 yles. The mximum mounts of I f1 /I nd I f2 /I rtios of PtNPs-CoNPs-FeNPs tlyst for EO retion during the 5 yles were.95 nd 1.39, 3 J Nnostrut 7(4): 292-38, utumn 217
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts respetively. PtNPs-CoNPs-FeNPs-CH tlyst hd the highest I f1 /I nd I f2 /I rtios fter 5 yles, inditing tht this tlyst is ple of offering exellent ntipoisoning effet towrd EO. Prmeters ffeting on eletrooxidtion of ethnol Our investigtions indited tht severl ftors suh s ethnol onentrtion, Fe nd Co mounts nd sn rte were the min prmeters influening the performne of the proposed modified eletrodes for ethnol eletrooxidtion. Effet of ethnol onentrtion Fig. 6 showed the effet of ethnol onentrtion on the nodi urrent density of EO on GC/PtNPs- jf1 / m m -2 24 2 16 12 8 4.2.4.6.8 1 1.2 [EtOH] / M B jf2 / m m -2 35 3 25 2 15 1 5.2.4.6.8 1 1.2 [EtOH] / M C 18 D 3 jf1 / m m -2 15 12 9 6 3.2.4.6.8 1 1.2 [EtOH] / M jf2 / m m -2 25 2 15 1 5.2.4.6.8 1 1.2 [EtOH] / M E 31 26 21 16 11 6 1-4.4.8 1.2 1.6 Fig. 6. Cyli voltmmogrms for EO on, B) PtNPs-CoNPs-CH ; C, D) PtNPs-FeNPs-CH nd E) PtNPs- CoNPs-FeNPs-CH eletrodes in.5 M H2SO4 in different onentrtion of ethnol: ).6, ).11, ).17, d).22, e).28, f).34, g).39, h).44, i).49, j).55, k).61, l).66, m).71, n).76, o).82, p).87, q).92, r).97, s) 1.2, t) 1.7 M. t J Nnostrut 7(4): 292-38, utumn 217 31
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts CoNPs-CH (Fig. 6, B) nd GC/PtNPs-FeNPs-CH (Fig. 6 C, D) eletrodes. It ws lerly oserved tht the nodi urrent density inreses with inresing ethnol onentrtion nd levels off t onentrtions higher thn 1.7 M. We ssume this effet my e due to the sturtion of tive sites on the surfe of the eletrode. This lso indites further tht the eletrooxidtion of ethnol t modified eletrode is ontrolled y diffusion proess. In ordne with this result, the optimum onentrtion of ethnol to otin higher urrent density my e onsidered s out 1.7 M. t GC/PtNPs-CoNPs-CH eletrode, when the ethnol onentrtion inreses from.6 to 1.7 M, the E f1 shifts towrds positive diretion from.742 to.789 V (Fig. 6) nd E f2 shifts towrds positive diretion from 1.126 to 1.219 V (Fig. 6B). Inresing the ethnol onentrtion from.6 to 1.7 M t GC/PtNPs-FeNPs-CH eletrode uses the shift in E f1 from.747 to.799 V (Fig. 6C) nd E f2 shifts towrds positive diretion from 1.133 to 1.211 V (Fig. 6D). This my result from the following reson: The inrese of the ethnol onentrtion will inrese the poisoning rte of the Pt tlyst nd use shift of the oxidtive removl of the strongly dsored intermedites to more positive potentil [33]. The effet of ethnol onentrtion ws lso investigted t GC/PtNPs-CoNPs-FeNPs-CH eletrode. Cyli voltmmogrms were otined in different onentrtions of ethnol. The sme ehvior ws oserved (Fig. 6E). t GC/PtNPs- CoNPs-FeNPs-CH eletrode, when the ethnol onentrtion inreses from.6 to 1.7 M, the E f1 shifts towrds positive diretion from.729 to.79 V nd E f2 shifts towrds positive diretion from 1.131 to 1.222 V. Effet of Fe nd Co nnoprtile mounts In order to determine the effet of Co nd Fe nnoprtile mounts, tlyti tivity of PtNPs- FeNPs-CH nd PtNPs-CoNPs-CH nnotlysts towrd ethnol eletrooxidtion ws investigted through LSV under different onentrtions of Fe nd Co nnoprtiles nd onstnt mount of Pt nnoprtiles (8mM) (Figs. 7, 7B). Fig. 7 showed LSV urves of PtNPs-FeNPs-CH nnoomposite with 8mM of Pt nnoprtiles nd different onentrtions.33,.99, 1.5 nd 2.9 mm of Fe nnoprtiles. s seen in Fig. 7, the est tlyti tivity ws oserved for PtNPs-FeNPs-CH with 8 mm Pt nd.33 mm Fe nnoprtiles. LSV urves of PtNPs-CoNPs-CH nnotlysts with onstnt mount (8 mm) of Pt nnoprtiles nd different onentrtion (.16,.33 nd.49 mm) of Co nnoprtiles were shown in Fig. 7B. Similrly, the est tlyti tivity ws oserved for PtNPs-CoNPs-CH with 8 mm Pt nd.33 mm Co nnoprtiles. Fig. 7. LSV urves of ) PtNPs-FeNPs-CH nnoomposite t 8mM PtNPs nd :.33, :.99, : 1.5, d: 2.9 mm of FeNPs nd B) PtNPs-CoNPs-CH nnoomposites t 8 mm of PtNPs nd :.16, :.33 nd :.49 mm of CoNPs. Effet of sn rte In order to investigte the effet of sn rte, the CV urves of PtNPs-CoNPs-CH, PtNPs-FeNPs- CH nd PtNPs-CoNPs-FeNPs-CH were otined t the sn rtes of 3, 5, 7, 1, 15 nd 2 mvs -1. Bsed on the CV urves, the nodi pek urrent density mounts of ethnol oxidtion vs. 25 2 15 1 5.3.6.9 1.2 1.5 d 3 25 2 15 1 5.3.6.9 1.2 1.5 Fig. 7. LSV urves of ) PtNPs-FeNPs-CH nnoomposite t 8mM PtNPs nd :.33, :.99, : 1.5, d: 2.9 mm of FeNPs nd B) PtNPs-CoNPs-CH nnoomposites t 8 mm of PtNPs nd :.16, :.33 nd :.49 mm of CoNPs. B 32 J Nnostrut 7(4): 292-38, utumn 217
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts the squre root of the sweeping rte nd the pek potentil vs. ln υ hve een displyed (Fig. 8). The experiments hve een done in 1.7 M ethnol nd.5 M H 2 medium t different sn rtes. s seen in Fig. 8, y inresing the pplied sweeping rte, the nodi pek urrent density of ethnol oxidtion hs een inresed. The liner reltionship (R 2 =.92 -.96) etween the squre root of the sn rte nd the first pek urrent density (j f1 ) nd lso liner reltionship (R 2 =.98 -.99) etween the squre root of the sn rte nd the seond pek urrent density (j f2 ) demonstrtes tht EO proess is ontrolled with diffusion of ethnol from the ulk solution to the eletrode surfe [34, 35]. s oserved in Fig. 8, the pek potentil of ethnol oxidtion (E f1 ) nd lso (E f2 ) mplified with inresing the sn rte, nd liner reltionship (R 2 =.94 -.98) etween E f1 nd ln (υ) nd lso liner reltionship (R 2 =.93 -.99) etween E f2 nd ln (υ) hs een otined. This shows tht ethnol oxidtion is n irreversile hrge trnsfer proess [36, 37]. jf1/ m m -2 136 124 112 1 ln υ / mv s -1 3 3.5 4 4.5 5 5.5 R 2 =.9563 R 2 =.9821 4 7 1 13 16 υ.5 / mv.5 s -.5.83.8.77.74 E f1 / V jf2 / m m -2 265 22 175 13 ln υ / mv s -1 3 3.5 4 4.5 5 5.5 R 2 =.9953 R 2 =.9942 4 7 1 13 16 υ.5 / mv.5 s -.5 1.34 1.28 1.22 1.16 1.1 E f2 / V B jf1 / m m -2 168 161 154 147 14 ln υ / mv s -1 3 3.5 4 4.5 5 5.5 R 2 =.9235 R 2 =.9731 4 7 1 13 16 υ.5 / mv.5 s -.5.97.87.77.67 E f1 / V B jf2 / m m -2 31 27 23 19 15 ln υ / mv s -1 3 3.5 4 4.5 5 5.5 R 2 =.9946 R 2 =.9763 4 7 1 13 16 υ.5 / mv.5 s -.5 1.3 1.25 1.2 1.15 1.1 E f2 / V C jf1 / m m -2 18 17 16 15 14 ln υ / mv s -1 3 3.5 4 4.5 5 5.5 R 2 =.9313 R 2 =.9425 4 7 1 13 16 υ.5 / mv.5 s -.5.88.84.8.76.72 E f1 / V jf2 / m m -2 33 285 24 195 15 ln υ / mv s -1 3 3.5 4 4.5 5 5.5 R 2 =.9835 R 2 =.934 4 7 1 13 16 υ.5 / mv.5 s -.5 1.35 1.3 1.25 1.2 1.15 1.1 Fig. 8. nodi urrent density (jf1 nd jf2) vs. squre root of sn rte (υ.5 ) nd irreversiility plot of pek potentil (Ef1 nd Ef2) vs. ln υ for ) PtNPs-FeNPs-CH, B) PtNPs-CoNPs-CH, C) PtNPs-CoNPs-FeNPs-CH eletrodes in 1.7 M ethnol nd.5 M H2SO4 t the sn rtes of 3, 5, 7, 1, 15 nd 2 mv s -1. C E f2 / V J Nnostrut 7(4): 292-38, utumn 217 33
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts Effet of temperture The effet of temperture on the eletrotlyti tivity of PtNPs-CoNPs-CH, PtNPs-FeNPs-CH nd PtNPs-CoNPs-FeNPs-CH nnotlysts towrd ethnol oxidtion ws investigted through CV urves otined in different tempertures rnging from 2 to 45 C (Fig. 9). s seen in Fig. 9, the nodi urrent density ws inresed with inresing of the temperture. In this wy, the mss trnsport is n importnt ftor for higher tivity. s oserved for PtNPs-FeNPs-CH nnotlyst in Fig. 9, when the temperture hnged from 2 to 45 C, j f1 inresed from 14.43 to 234.35 m m -2 nd j f2 inresed from 223.59 to 329.91 mm -2. For PtNPs-CoNPs-CH nnotlyst, when the temperture inresed from 2 to 45 C, j f1 inresed from 169.46 to 232.36 m m -2 nd j f2 inresed from 266.88 to 349.23 m m -2 s shown in Fig. 9B. The effet of temperture on the tlyti tivity of PtNPs-CoNPs-FeNPs-CH for ethnol 2.4 y = -939.49x + 5.3323 4 e 2.32 2.24 2.16 32 2.8 24 16 8 325 26 195 13 65.3.6.9 1.2 1.5.4.8 1.2 1.6 E /V vs. SCE log j f1 / m m -2 logj f2 / m m -2 2.51 2.46 2.41 2.36 2.31.31.32.33.34.35 T -1 / K -1 y = -675.45x + 4.6462.31.32.33.34.35 T -1 / K -1 B 39 f 2.4 y = -56.81x + 3.9451 log j f1 / m m -2 2.35 2.3 2.25 2.2 log j f2 / m m -2.31.32.33.34.35 T -1 / K -1 2.55 2.5 2.45 2.4 y = -434.48x + 3.9.31.32.33.34.35 T -1 / K -1 C 42 2.45 y = -478.15x + 3.888 f 2.38 35 E 2 j /m m -2 28 21 14 7 E 1.4.8 1.2 1.6 log j f1 / m m -2 2.31 2.24 2.17.31.32.33.34.35 2.6 2.55 2.5 2.45 2.4 T -1 / K -1 y = -421.49x + 3.8972.31.32.33.34.35 T -1 / K -1 Fig. 9. Cyli voltmmogrms nd rrhenius plots of the logrithm of exhnge urrent density (log jf) versus the reiprol of temperture (T-1) of ) PtNPs-FeNPs-CH, B) PtNPs-CoNPs-CH nd C) PtNPs-CoNPs-FeNPs-CH nnotlysts in different tempertures of ) 2, ) 25, ) 3, d) 35, e) 4 nd f) 45 C log j f2 / m m -2 34 J Nnostrut 7(4): 292-38, utumn 217
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts eletrooxidtion ws shown in Fig. 9C. s seen in Fig. 9C, when the temperture inresed from 2 to 45 C, j f1 inresed from 172.21 to 232.96 m m -2 nd j f2 inresed from 277.24 to 358.24 m m -2. s seen for ll the tlysts, the ethnol oxidtion tivity ws enhned s the temperture inresed. t the sme ethnol onentrtion, the higher urrent density indited tht the nno sized tlysts possess more ville tive sites of three metls to prtiipte in the eletrohemil retion. tivtion energies were lulted y investigting the EO retion t different tempertures etween 2 nd 45 C on GC/ PtNPs-FeNPs-CH, GC/PtNPs-CoNPs-CH nd GC/ PtNPs-CoNPs-FeNPs-CH eletrodes. rrhenius plots of logrithm of exhnge urrent density (log j p ) versus the reiprol of temperture (T -1 ) were shown in Fig. 9. tivtion energies were lulted from the slope of the rrhenius plots for ertin potentil vlues using Eq. (13): ln j p / (1/T)=E /R (13) The pprent tivtion energy of the first nodi pek of ethnol eletrooxidtion (E 1 ) t PtNPs-FeNPs-CH, PtNPs-CoNPs-CH nd PtNPs- CoNPs-FeNPs-CH eletrodes ws 7.81, 4.21 nd 3.97 kj mol -1, respetively. The tivtion energy of the seond nodi pek of ethnol oxidtion (E 2 ) t PtNPs-FeNPs-CH, PtNPs-CoNPs-CH nd PtNPs- CoNPs-FeNPs-CH eletrodes ws 5.62, 3.61 nd 3.5 kj mol -1, respetively. Lower tivtion energy of ethnol eletrooxidtion t PtNPs-CoNPs- FeNPs-CH eletrode indited tht this eletrode hs etter tlyti tivity thn other prepred tlysts towrd ethnol eletrooxidtion. mperometri i-t urve mesurements The tivities of the prepred tlysts towrd EO mesured y stedy stte urrent densities t onstnt potentil were used for ompring the tlyti performne of ll s-prepred tlysts. mperometri i-t urve mesurements were rried out t potentil vlue 1 V in 1.7 M ethnol nd.5 M H 2 (Fig. 1). Fig. 1 showed the mperometri i-t urves of PtNPs- CH, PtNPs-FeNPs-CH, PtNPs-CoNPs-CH nd PtNPs-CoNPs-FeNPs-CH nnoomposites with the onentrtions of Pt (8 mm), Fe nd Co nnoprtiles (.33 mm). s seen in Fig. 1, the initil high urrent densities orrespond to the doule-lyer hrging [38]. ll potentiostti urrents deresed rpidly in the initil stge. fter period of 8 s, the urrent dey eme grdul nd then remined stle. fter 1 s, the urrent density of ll the tlysts eme lmost onstnt. The stedystte prt of the urve indited tht the stle urrent of PtNPs-CoNPs-FeNPs-CH eletrode ws higher thn in the other three tlysts. This result reveled tht PtNPs-CoNPs-FeNPs-CH tlyst hs the highest eletrotlyti tivity towrd ethnol eletrooxidtion nd the highest stility. Thus, PtNPs-CoNPs-FeNPs-CH tlyst seems to e promising ndidte for the diret ethnol fuel ell pplitions. Eletrotlyti tivity of GC/PtNPs- CoNPs-FeNPs-CH eletrode towrd ethnol eletrooxidtion ws lso investigted with different onentrtion of Fe nd Co nnoprtiles. In order to investigte the effet of FeNPs onentrtion, hronomperometry urves were otined in the onstnt mount of Co nnoprtiles (.33 mm) nd different onentrtions (.33,.99, 2.9 mm) of Fe nnoprtiles (Fig. 1B). To determine the effet of Co onentrtion on the tlyti tivity of GC/PtNPs-CoNPs- FeNPs-CH eletrode for ethnol eletrooxidtion, onstnt mount of Fe nnoprtiles (.33 mm) nd different onentrtion of CoNPs (.16,.33,.49 mm) were used (Fig. 1C). The est result ws oserved for PtNPs-CoNPs-FeNPs-CH nnoomposite with Pt 8 mm, Co.33 mm nd Fe.33 mm omposition. CONCLUSIONS In this work, Pt-M-hitosn (M = Co, Fe) nnoomposites dispersed in hitosn polymer were suessfully synthesized nd hrterized. The GC/PtNPs-CoNPs-CH, GC/PtNPs-FeNPs- CH nd GC/PtNPs-CoNPs-FeNPs-CH eletrodes were prepred s tive eletrotlysts for eletrooxidtion of ethnol. Good dispersion of the metl nnoprtiles shown in the TEM imges reveled tht hitosn is good support for preprtion of the metl nnoprtiles. Our results showed tht, inorportion of Co nd Fe nnoprtiles into the Pt tlyst n improve the eletrode performne for ethnol eletrooxidtion. The tivity of PtNPs-CoNPs- FeNPs-CH for ethnol eletrooxidtion in id medium ws higher thn tht of PtNPs-CoNPs- CH, PtNPs-FeNPs-CH nd lso muh higher J Nnostrut 7(4): 292-38, utumn 217 35
M. S Ekrmi-Kkhki et l/ Eletrotlyti tivity of Pt-M (M= Co, Fe) Chitosn Supported Ctlysts 32 24 16 8 1 2 3 4 5 t / s d B 32 C B 32 32 C 32 24 24 24 24 16 16 16 16 8 8 8 8 1 2 3 4 5 1 2 3 4 5 t / s 1 2 3 4 5 t / s 1 2 3 4 5 t / s t / s Fig. 1. Chronomperometry for EO t ) ll prepred tlysts, B) GC/PtNPs-CoNPs-FeNPs-CH eletrotlyst with.33 mm of CoNPs nd different onentrtions of FeNPs: ).99, ) 2.9, ).33 mm nd C) GC/PtNPs- CoNPs-FeNPs-CH eletrotlyst with.33 mm of FeNPs nd different onentrtions of CoNPs: ).16, ).49, ).33 mm in 1.7 M ethnol nd.5 M H2SO4. thn tht of PtNPs-CH tlyst due to its higher urrent density, lower nodi pek potentil, higher eletrohemilly tive surfe re nd etter ntipoisoning effet towrd EO otined fter 5 yles. This result ws onfirmed with ompring of the tivtion energy, the mperometri i-t urves, the CO stripping nd the EIS investigtions of the prepred tlysts. The CO stripping investigtions showed tht PtNPs-CoNPs-FeNPs-CH tlyst hd higher CO tolerne thn other prepred tlysts. CO produed from ethnol dissoition n e esily oxidized to CO 2 on this tlyst. In this se the CO poisoning of PtNPs-CoNPs-FeNPs-CH tlyst ws lower thn other s-prepred tlysts. ll the investigtions reveled tht PtNPs-CoNPs- FeNPs-CH tlyst hd the est tlyti tivity towrd ethnol eletrooxidtion. CKNOWLEDGMENT We thnk Esfryen University of Tehnology for finnil support. CONFLICT OF INTEREST The uthors delre tht there re no onflits of interest regrding the pulition of this mnusript. REFERENCES 1. Solimn B, del-smd HS, del Rehim SS, hmed M, Hssn HH. High Performne Nno-Ni/Grphite Eletrode for Eletro-oxidtion in Diret lkline Ethnol Fuel Cells. J. Power Soures, 216; 325: 653-663. 2. ntonissi RM, Otuo L, Vz JM, Oliveir Neto, Spiné EV. Synthesis of Pt Nnoprtiles with Preferentil (1) Orienttion Diretly on the Cron Support for Diret Ethnol Fuel Cell. J. Ctl., 216; 342: 67-74. 3. Mo H, Hung T, Yu. Surfe Nole Metl Modified PdM/C (M=Ru, Pt, u) s node Ctlysts for Diret Ethnol Fuel Cells. J. lloy. Compd., 216; 676: 39-396. 4. Liu X, Dun J, Chen H, Zhng Y, Zhng X. Cron Riveted Pt/Grphene Ctlyst with High Stility for Diret Methnol Fuel Cell. Miroeletron. Eng., 213; 11: 354-357. 5. Higuhi E, Tkse T, Chiku M, Inoue H. Preprtion of Ternry Pt/Rh/SnO2 node Ctlysts for Use in Diret Ethnol Fuel Cells nd Their Eletrotlyti tivity for Ethnol Oxidtion Retion. J. Power Soures, 214; 263: 28-287. 6. Kérnguéven G, Berná, Sier E, Feliu JM, Léger JM. Dimethoxymethne Eletrooxidtion on Low Index Plnes of Pltinum Single Crystl in id Medi. Eletrohim. t, 28; 54 (2): 394-42. 7. Shin JH, Yoon JH, Lee SH, Prk TH. Hydrogen Prodution from Formi id in ph-stt Fed-Bth Opertion for Diret Supply to Fuel Cell. Bioresour. Tehnol., 21; 11 (1): S53- S58. 8. Fro ML, Ros DL, Nioter I, ntonui V, Slvtore riò 36 J Nnostrut 7(4): 292-38, utumn 217
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