Chinese Chemicl Letters 26 (215) 1322 1326 Contents lists vilble t ScienceDirect Chinese Chemicl Letters journl homepge: www.elsevier.com/locte/cclet Originl rticle n oxygen reduction sensor bsed on novel type of porous crbon composite membrne electrode En-Dong Xing [2_TD$DIF], Long-Qi Ling [3_TD$DIF], Yu-Jie Dong b, Wei-Min Hung [4_TD$DIF], * [5_TD$DIF] College of Chemistry, Jilin University, Chngchun 1312, Chin b Emergency Deprtment, Chin Jpn Union Hospitl of Jilin University, Chngchun 1333, Chin RTICLE INFO STRCT rticle history: Received 13 Februry 215 Received in revised form 19 Mrch 215 ccepted 7 My 215 vilble online 3 June 215 Keywords: Oxygen Sensor Porous crbon composite membrne Electrode The development of simple, efficient nd sensitive sensor for dissolved oxygen is proposed using novel type of porous crbon composite membrne/glssy crbon electrode bsed on the low-cost common filter pper by simple method. The resulting device exhibited excellent electroctlytic ctivities towrd the oxygen reduction rection. Scnning electron microscopy, trnsmission electron microscopy, X-ry photoelectron spectroscopy nd electrochemicl mesurements demonstrted tht the porous morphology nd uniformly dispersed Fe 3 C nnoprticles of the PCCM ply n importnt role in the oxygen reduction rection. liner response rnge from 2 [7_TD$DIF]mmol/L up to 11 mmol/l nd detection limit of 1.4 mmol/l ws obtined with this sensor. The repetbility of the proposed sensor, evluted in terms of reltive stndrd devition, ws 3.%. The successful fbriction of PCCM/GC electrode my promote the development of new porous crbon oxygen reduction rection mteril for the oxygen reduction sensor. ß 215 Chinese Chemicl Society nd Institute of Mteri Medic, Chinese cdemy of Medicl Sciences. Published by Elsevier.V. ll rights reserved. 1. Introduction Interest in the development of dissolved oxygen sensing devices is very extensive in the environmentl, medicl nd industril fields [1]. When compred to other techniques employed for oxygen determintion, such s opticl methods, electrochemicl techniques hve the dvntges of simplicity nd high sensitivity. The oxygen reduction rection (ORR) is the key point in the process, where the mount of dissolved oxygen cn improve or inhibit the process [2]. In order to promote the development nd wide ppliction of sensor, studies to identify (or determine) n efficient, chep, stble, nd green non-precious metl ORR ctlyst hve been top priority [3 5]. Hence, btch syntheses of well-controlled nd low-cost crbon composite ORR ctlysts becme one of the gretest current chllenges in the field of preprtion of non-precious metl ORR ctlyst [6 18]. To dte, there exists tremendous preoccuption in exploring simple method to prepre stble crbon composites from renewble biomss resources including soy milk, wood, bmboo, fruits, kenf stem, egg white, nd bcteri for potentil pplictions in super * Corresponding uthor. E-mil ddress: hungwm@jlu.edu.cn (W.-M. Hung). cpcitors, energy storge, electronlyticl chemistry, nd electroctlysts [19 23]. The Ji group hd prepre porous crbon composite membrne (PCCM) from low-cost common filter pper (FP) which cts s the crbon precursor [24 26]. The Fe-bsed nnoprticles formed on the composite surfce during the pyrolysis my further improve the electroctlytic ORR ctivity of the PCCM, nd the porous rchitecture of this FP-derived composite is beneficil to O 2 dsorption nd trnsport during the ORR process. In order to investigte the chrcteristics of the PCCM, we fbricted the PCCM on the surfce of the GCE. The electrochemicl properties of the PCCM coted glssy crbon electrode for reducing dissolved oxygen in n lkline environment were investigted. In this context, the present work reports on the development of n efficient nd stble sensor for oxygen determintion bsed on the construction of novel PCCM produced from low-cost common FP, which cts s the crbon precursor on the surfce of GCE. The resulting simple, cost-effective, sensitive, nd selective dissolved oxygen sensor exhibits fst response (1 s to rech stedy stte) nd low detection limit. Optimiztion of the experimentl conditions yielded detection limit nd sensitivity for O 2 much better thn those described in the literture. This sensor showed good repetbility for both the electrode preprtion nd determintions, evluted in term of reltive stndrd http://dx.doi.org/1.116/j.cclet.215.5.43 11-8417/ß 215 Chinese Chemicl Society nd Institute of Mteri Medic, Chinese cdemy of Medicl Sciences. Published by Elsevier.V. ll rights reserved.
E.-D. Xing et l. / Chinese Chemicl Letters 26 (215) 1322 1326 1323 devitions, s well s llied with simple nd esy method of preprtion. In view of these intrinsic dvntges, this novel type of porous crbon composite membrne would become nnostructure mtrix extensively pplied in the field of oxygen reduction sensors 2. Experimentl 2.1. Chemicls Filter pper ws bought from Hngzhou Xinhu pper (Hngzhou, Chin). Nfion (5. wt%) were purchsed from Sigm ldrich. Iron nitrte nd methnol were bought from eijing Chemicl Regent Compny (eijing, Chin). ll the chemicls were nlyticl grde, nd used s received. ll queous solutions were prepred with ultrpure wter from Wter Purifier System (Sichun Wter Purifier Co[8_TD$DIF]., Ltd., Chin). 2.2. pprtus Electrochemicl mesurements were performed on CHI 66 Electrochemicl nlyzer (Co., CHI, US) with conventionl three-electrode system comprised of pltinum wire s uxiliry electrode, n g/gcl (sturted KCl) electrode s the reference electrode nd glssy crbon electrode (GCE, dimeter 3 mm) s working electrode. Rotting ring-disk electrode (RRDE) techniques were employed on Model RRDE-3 pprtus (LS, Jpn) with CHI84 Electrochemicl Worksttion. Scnning electron microscopy (SEM) imges with n ccelerting voltge of 2 kv were obtined on n XL 3 ESEM FEG SEM (Philips, Netherlnds). Trnsmission electron microscopy (TEM) mesurements were mde on HITCHI H-81 EM with n ccelerting voltge of 1 kv. X-ry photoelectron spectroscopy (XPS) nlysis ws obtined on n ESCLMKII X-ry photoelectron spectrometer (VG Scientific, UK). 2.3. Preprtion of porous crbon composite membrne nd electrode The commercil filter pper ws stbilized t 24 8C for 2 h in muffle furnce t heting rte of 2 8C/min. Then the mteril ws impregnted with known concentrtion of Fe(NO 3 ) 3, nd dried t room temperture. Finlly, the ctlyst ws prepred by temperture-progrmming in tube furnce under N 2 t heting rte of 2 8C/min, The finl product ws bsed on the pyrolysis temperture (9 8C) nd concentrtion of Fe(NO 3 ) 3 (1.%), respectively [11]. efore modifiction, the GCE ws polished crefully using.3 mm lumin slurries, followed by soniction successively in cetone, ethnol nd ultrpure wter, nd then dried t room temperture. For typicl procedure, 4. mg of the PCCM smple [(Fig._1)TD$FIG] were dissolved in mixture (4 ml) of wter, isopropyl lcohol, nd Nfion (5. wt%) t rtio of 2:1:.75 (v/v/v) under soniction. For the electrochemicl mesurements, certin mount of the PCCM suspension ws coted onto the pretreted GCE surfce, nd then the PCCM/GCE ws dried under n infrred lmp before use. 2.4. Electrochemicl mesurements The cyclic voltmmetric nd mperometric experiments were performed in thermostted electrochemicl cell t 25 8C. mperometric experiments were crried out in.1 mol/l KOH solution with stirring by pplying potentil step of.29 V. When the current reched stedy-stte vlue, substrte ws dded t one smple per 8 s. Different volumes of n O 2 -sturted solution were spiked into N 2 -sturted.1 mol/l KOH for the detection of dissolved oxygen. In the RRDE experiments, liner sweeping voltmmogrms (LSVs) were obtined by performing negtive-direction sweep of potentil from.2 V t rte of 5 mv/s, with the ring potentil set t.2 V in.1 mol/l KOH. efore beginning experiments, ll the modified electrodes nd the Pt ring electrode were ctivted by potentil cycling in.1 mol/l KOH from.2 [9_TD$DIF]V to.8 V t scn rte of 5 mv/s for 3 cycles. 3. Results nd discussion 3.1. Physicl nd chemicl chrcteriztion of porous crbon composite membrne electrode The trnsmission electron microscopy (TEM) results (Fig. 1) of these mterils re consistent with the SEM imges. The trnsmission electron microscopy (TEM) of the porous crbon composite membrne exhibited reltive homogeneous morphology with uniformly dispersed nnoprticles ner, or, in the pores, nd the dimeters of the prticles rnging from 3 [1_TD$DIF]nm to 1 nm. ecuse the oxidtive gses, such s NO 2,O 2, nd NO, will be relesed when Fe(NO 3 ) 3 melts t high tempertures [27], there re some pores which ppered on the surfce of the PCCM. The highresolution TEM imges shown in Fig. 2 re tken from the PCCM. The distnces of.21 [1_TD$DIF]nm nd.376 nm re corresponding to (2 1 1) nd ( 1 1) crystl plnes of Fe 3 C phse, respectively, nd the Fe 3 C nnoprticles re surrounded by the crbon shells [5,28]. The XPS nlysis cn provide dditionl informtion bout the oxygen-contining surfce groups. The XPS nlysis indictes the PCCM is minly composed of C (284.6 ev), O (532.5 ev), nd Fe (711.5 ev), confirming tht Fe hs been successfully doped into the crbon composite (Fig. 3). In detil, the spectr of Fe 2p (Fig. 3) of the PCCM revel the distribution of Fe 2p into two species: Fe 2p 3/2 nd Fe 2p 1/2 observed t 71.5 [12_TD$DIF]eV nd 723.9 ev, respectively, from Fig. 1. TEM imge of () PCCM nd () SEM imge of PCCM.
[(Fig._2)TD$FIG] 1324 E.-D. Xing et l. / Chinese Chemicl Letters 26 (215) 1322 1326 Fig. 2. High resolution TEM imges of the PCCM. The distnces of.21 nm () nd.376 nm () correspond to (2 1 1) nd ( 1 1) crystl plnes of Fe 3 C phse, respectively. [(Fig._3)TD$FIG] Intensity (.u.) C 1s Fe 2p O 1s 284.61 ev 711.46 ev 532.46 ev Intensity (.u.) 2 4 6 8 1 12 inding energy/ev 525 53 535 54 545 inding energy/ev Fig. 3. () XPS survey for the resultnt PCCM nd () high-resolution Fe2p spectr. which we cn deduce tht iron toms in the ctlyst re either in the metllic, oxidtion, or crbidic stte [28]. Recent studies hve verified tht the encsed Fe 3 C ctivtes the surrounding grphitic lyers, mking the outer surfce of the crbon lyer ctive towrd the ORR [29]. Therefore, the s-prepred PCCM with evenly dispersed Fe 3 C nnoprticles should find ppliction in the ORR. 3.2. Electrochemicl mesurements of dissolved oxygen In the potentil window from +.2 [13_TD$DIF]V to.8 V, fter bubbling the detection solution thoroughly with high purity nitrogen for 5 min, the PCCM electrode begn to reduce dissolved oxygen t [(Fig._4)TD$FIG] I/µ 1-1 -2-3 -4 1-1 -2-3 -4 -.9 b -.75 b -.6 -.45 -.3 -.15 E/V vs g/gcl..15.3 Fig. 4. Cyclic voltmmogrms of re GCE () nd PCCM/GCE () in N 2 -sturted.1 mol/l KOH () nd O 2 -dissolved.1 mol/l KOH (b) scn rte is 5 mv/s (vs g/ gcl). bout.15 V in.1 mol/l KOH. The cyclic voltmmogrms showed n obvious reduction pek centered t bout.29 V (Fig. 4), while t the bre GCE negtive shift of the smller reductive pek ws observed in the scn rnge. Compred to other modified electrodes, the PCCM modified glssy crbon electrode displys superior ORR ctivity which hs more positive reduction pek potentil, onset potentil, nd higher reduction current density in O 2 -sturted.1 mol/l KOH. The kinetics of ORR of the PCCM/GCE ws further studied by liner sweeping voltmmogrms t 16 rpm using rotting ring disk electrode (RRDE). Notbly, the number of trnsferred electrons (n) is clculted from the ring nd disk currents, nd is observed to be 3.82 3.97 over the entire investigted potentil rnge (Fig. 5). s shown in Fig. 5, the H 2 O 2 yield of the PCCM/ GCE is below 17.3% over the potentil rnge of.2 to.65 V in O 2 -sturted.1 [1_TD$DIF]mol/L KOH bsed on the ssumption tht oxygen rects in prllel mechnism [3]. ll of these conclusions indicte tht the fbricted PCCM/GCE possesses superior electroctlytic ORR ctivity nd four-electron trnsfer process is predominnt. 3.3. The sensor chrcteristics The nlyticl performnce of the sensor ws verified by mperometry. In these mesurements, n initil study ws performed in order to determine the best potentil to be pplied to the electrode. The pplied potentil ws chosen bsed on mesurements of the ctlytic current using the optimized conditions nd the highest current verified t n pplied potentil of.29 V versus g/gcl. The mperometric trce recorded t.29 V of the PCCM electrode displyed in Fig. 6 during the
[(Fig._5)TD$FIG] E.-D. Xing et l. / Chinese Chemicl Letters 26 (215) 1322 1326 1325 J ring -1 2-2 J/(m/cm 2 ) -3-4 H 2 O 2 % -5 J disk -6 -.8 -.6 -.4 -.2 E/V..2.4 -.7 -.6 -.5 -.4 E/V -.3 -.2 Fig. 5. () RRDE voltmmogrms of PCCM/GCE in O 2 -sturted.1 [1_TD$DIF]mol/L KOH t scn rte of 5 mv/s, rottion rte of 16 rpm. Inset: electron trnsfer number (n) nd () H 2 O 2 yield of PCCM/GCE. [(Fig._6)TD$FIG] I/µ 25 2 15 1 5 2 4 6 t /s 8 1 12 electrode ws stored t room temperture no significnt chnge in the response ws observed fter more thn 2 months. The effects of substnces tht might interfere with the response of the PCCM electrode were studied (Tble 1). The inhibition current obtined for ech interfering substnce present t concentrtion of 11 mmol/l ws compred with the current obtined in the presence of 11 mmol/l O 2, nd this rtio ws used s criterion for the selectivity of the sensor. s cn be verified, the observed influences re ll less thn 3% on the dissolved oxygen response. These results revel tht the fbricted sensor cn tolerte high concentrtions of interfering species nd, therefore, cn be climed s selective in the presence of the commonly encountered foreign species. Fig. 6. Typicl stedy-stte current response of the PCCM/GCE to successive dditions of different volumes of O 2 -sturted solution into N 2 -sturted.1 mol/l KOH. pplied potentil,.29 V. Inset: clibrtion curve of the electroctlytic current on the concentrtion of oxygen. spiking of different volumes of O 2 -sturted solution into N 2 - sturted KOH solution, illustrtes tht the modified electrode responds very rpidly to these chnges in the O 2 concentrtion, producing stedy-stte signls within 1 s. The response displyed liner rnge from 2 [7_TD$DIF]mmol/L to 11 mmol/l with correltion coefficient of.999. The limit of detection is 1.4 mmol/l t the signl to noise rtio of 3. The high sensitivity is ttributed to the excellent ctlytic ctivity of uniformly dispersed Fe 3 C nnoprticles of the membrne. Repeted use of the electrodes did not ffect the long-term stbility. The coefficients of vrition of the current signls for ten repeted injections of two nd 2 mmol/l of O 2 were 2.6 nd 3.%, respectively. The modified electrode showed cceptble preprtion reproducibility with reltive stndrd devition of 3.% estimted from the slopes of the clibrtion plots on eight freshly prepred PCCM/GC electrodes. When the modified 4. Conclusion We hve demonstrted simple method for the fbriction of n oxygen reduction sensor bsed on novel PCCM/GC electrode from renewble, low-cost filter pper. The PCCM electrode shows excellent electroctlytic ctivity towrd the electroreduction of dissolved oxygen nd cn thus be used for highly sensitive detection of dissolved oxygen. The results indicted tht the porous structure nd the Fe-bsed nnoprticles gretly improved the electroctlytic ORR ctivity of the PCCM electrode. Therefore, the successful fbriction of PCCM/GCE is more menble to lrgescle production due to the chep crbon precursor nd the simple, two-step synthetic process for the oxygen reduction sensor. cknowledgments We cknowledge finncil supports from the Ntionl Nturl Science Foundtion of Chin (No. 2127397), the project from the Stte Key Lbortory of Electronlyticl Chemistry (No. 213) nd the Science Foundtion of Jilin Province (No. 213243GX)[14_TD$DIF]. Tble 1 Inhibition of the interferences to the PCCM/GC electrode. Potentil interfering substnce Current rtio (%) Li +.9 N + 1.1 + NH 4.8 NO 3 1.3 2 SO 4 1.5 Methnol 1.6 Current rtio is the current of interfering substnce compred with tht of 11 mmol/l O 2. References [1] W. Glsspool, J. tkinson, screen-printed mperometric dissolved oxygen sensor utilising n immobilised electrolyte gel nd membrne, Sens. ctutors : Chem. 48 (1998) 38 317. [2] R. Mrtínez-Máñez, J. Soto, J. Lizondo-Sbter, et l., New potentiomentric dissolved oxygen sensors in thick film technology, Sens. ctutors : Chem. 11 (24) 295 31. [3] S. Shnmugm, T. Osk, Efficient electroctlytic oxygen reduction over metl free-nitrogen doped crbon nnocpsules, Chem. Commun. 47 (211) 4463 4465. [4]. Morozn, P. Jégou, S. Cmpidelli, S. Plcin,. Jousselme, Reltionship between polypyrrole morphology nd electrochemicl ctivity towrds oxygen reduction rection, Chem. Commun. 48 (212) 4627 4629.
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