- Email: [email protected]
O2 biofuel cell base on nanographene platelet-modified electrodes
Electrochemistry Communications 12 (2010) 869–871
Contents lists available at ScienceDirect
Electrochemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e l e c o m
A glucose/O2 biofuel cell base on nanographene platelet-modified electrodes W. Zheng a, H.Y. Zhao a, J.X. Zhang a, H.M. Zhou a, X.X. Xu a, Y.F. Zheng a,b,⁎, Y.B. Wang b,c, Y. Cheng c, B.Z. Jang d a
Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001, China Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871, China c Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China d College of Engineering and Computer Science, Wright State University, 3640 Colonel Glenn Hwy., Dayton, OH 45435, USA b
a r t i c l e
i n f o
Article history: Received 22 March 2010 Received in revised form 8 April 2010 Accepted 9 April 2010 Available online 13 May 2010 Keywords: Biofuel cell Nanographene platelets Glucose oxidase Laccase
a b s t r a c t This study demonstrated a novel nanographene platelets (NGPs)-based glucose/O2 biofuel cell (BFC) with the glucose oxidase (GOD) as the anodic biocatalysts and the laccase as the cathodic biocatalysts. The GOD/ NGPs-modified electrode exhibited good catalytic activity towards glucose oxidation and the laccase/NGPsmodified electrode exhibited good catalytic activity towards O2 electroreduction. The maximum power density was ca. 57.8 μW cm− 2 for the assembled glucose/O2 NGPs-based BFC. These results indicated that the NGPs were very useful for the future development of novel carbon-based nanomaterials BFC device. © 2010 Elsevier B.V. All rights reserved.
1. Introduction
2. Experimental
The enzyme-based biofuel cell (BFC) is a special fuel cell using enzyme as catalyst and can directly convert chemical energy to electrical energy [1]. BFC has a potential application prospect due to its good biocompatibility and wide source of raw materials, which have attracted considerable research attention [1–3]. Some disadvantages such as deactivation, poor stability and low electron-transfer rate of enzyme become the bottleneck for the development of high quality BFC. In order to solve these problems, great efforts have been made by incorporating enzymes into appropriate matrix [4]. Nanoscale graphene platelet, consisting of nanometer-sized twodimensional graphene fragments with honeycomb lattice, is an emerging class of carbon-based nanomaterials [5]. In contrast to fulleren and carbon nanotube, NGPs have closed π-electron systems and feature as a twodimensional extended electronic structure of π-electrons with open edges. Thus it is considered as a rising star in carbon-based nanomaterial family for electrochemical applications [6]. In the present study, the NGPs were used as the matrix of anode catalyst GOD and cathode catalyst laccase, and the electrochemical performance of glucose/O2 BFC using NGPs as the substrates for both bioanode and biocathode was further investigated.
The fabrication details of NGPs can be found in our previous work [5]. The experimental NGPs were dried under vacuum at 100 °C for 24 h to remove the residual organic solvent prior to use. They were dispersed into aqueous solution to give a 2 mg mL− 1 homogeneous dispersion, then 8 µL of the dispersion was dip-coated onto the glassy carbon (GC) electrodes, followed by a period of standing in air until dry (denoted as NGPsmodified GC electrodes). The NGPs-modified GC electrodes were immersed into 10 mg mL− 1 glucose oxidase (GOD, Type X-S from Aspergillus niger, EC 1.1.3.4, 50 kU g− 1 solid) solution for 12 h, and then 2 µL of the Naifion solution (2 wt.%) was further introduced to form a tight membrane on the enzyme electrode. Laccase (E.C. 1.10.3.2, from Trametes versicolor, purchased from Fluka) was purified following the method reported previously by the present authors [7]. A 8 µL laccase–bovine serum albumin mixture (3/1 v/v) was spread evenly onto the NGPsmodified GC electrode and then cross-linked with 2µL glutaraldehyde (40 mM) onto the electrode, allowing the solution at the electrode to be dried up at an ambient temperature (denoted as laccase/NGPs-modified GC electrodes). All the electrochemical measurements were carried out using a computer-controlled electrochemical analyzer (CHI 650C, Chen-Hua, Shanghai). A conventional three-electrode cell was used, the modified electrodes as working electrodes, a platinum spiral wire as the counter electrode and a saturated calomel electrode (SCE) as the reference electrode. For the experiments conducted under anaerobic conditions, the electrolyte was bubbled with pure N2 for more than 30 min, and N2 was kept flowing over the solution during the electrochemical
⁎ Corresponding author. Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871, China. E-mail address: [email protected] (Y.F. Zheng). 1388-2481/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2010.04.006
870
W. Zheng et al. / Electrochemistry Communications 12 (2010) 869–871
measurements. For assembling an ascorbate/O2 biofuel cell, the GOD/ NGPs-modified electrode was used as the anode for the oxidation of glucose and the laccase/NGPs-modified electrode was used as the cathode for the O2 reduction. Nafion film was sandwiched as a separator
Fig. 1. (A) CVs of GOD/NGPs-modified GC (solid line) electrode at 100, 200, 300, 400, 500, 600, 700, 800 and 900 mV s− 1 (from inner to outer) and CVs of GOD/GC (dashed line) electrode at 100 mV s− 1 in air-saturated 0.10 M phosphate buffer. Inset showed a plot of cathodic and anodic peak currents against potential scan rate. (B) CVs of GOD/NGPsmodified GC electrodes in 0.10 M phosphate buffer solution containing 0.50 mM ferrocene monocarboxylic acid in the different concentrations of glucose. Scan rate: 10 mV s− 1. (C) CVs of laccase/NGPs-modified GC electrode in N2 (blue line) and air (red line), and CVs of NGPs-modified GC electrode in air (black line) saturated 0.10 M pH 6.0 phosphate buffer containing 1.0 mM ABTS. Scan rate: 10 mV s− 1. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
between two bioelectrodes. All electrochemical measurements were performed at least three times at 20± 2 °C. 3. Results and discussion Fig. 1A shows the CVs of the NGPs-modified GC electrode, GOD/ NGPs-modified GC electrode and GOD/GC electrode in 0.10 M phosphate buffer (pH 6.0) at a scan rate of 100 mV/s. No obvious redox peaks were observed for the GC electrode within the potential window (dashed line in Fig. 1A). However, a pair of well-defined quasi-reversible redox peaks was visible at −0.48 V and − 0.41 V (vs. SCE) for the GOD/NGPs-modified GC electrode (solid line in Fig. 1A). The separation of peak potentials and the formal potential were calculated to be ca. 70 mV and −0.445 V (vs. SCE), respectively, and corresponded to the electrode process of the FAD/FADH2 redox of the electroactive center of GOD [8]. As a control experiment, the electrochemistry of GOD at the GC electrodes was also studied and a pair of slight redox peaks was found (inset in Fig. 1A), but the peak currents were remarkably smaller than that obtained on the GOD/ NGPs-modified GC electrode, indicating that the presence of NGPs could facilitate the direct electron transfer of the GOD and enhance the electrochemical signal, which coincided well with the previous report [9]. It may be due to the fact that the large surface-to-volume ratio and high conductivity of NGPs could lead to the efficient realization of direct electron transfer between redox enzymes and the surface of electrode. NGPs in the sensing interface might act as an enhancing agent for effective acceleration of electron transfer between matrix and GOD, leading to more rapid current response for GOD [10]. In addition, the cathodic peak current was almost equal to the anodic peak current suggesting that the GOD adsorbed onto the surface underwent a reversible direct electrochemical reaction with two-electron transfer. Moreover, the cathodic and anodic peak currents (Ip) of the GOD increased with the increase of the scan rate (v) in the range from 100 to 900 mV s− 1, whereas the cathodic and anodic peak potentials exhibited a small shift, which was indicative of a fast electron-transfer rate. In order to confirm the enzymatic activity of the immobilized GOD on the NGPs-modified GC electrode, the electrocatalysis of GOD toward glucose was measured as shown in Fig. 1B. In the air-saturated phosphate buffer solution containing 0.50 mM ferrocene monocarboxylic acid (FMCA) as the mediator, a couple of well-defined redox peaks (black curve) appeared, corresponding to the redox reaction of FMCA [11]. When glucose was added into the buffers, the anodic peak current increased significantly at about +0.31 V (vs. SCE), accompanying with a decrease of the cathodic peak current. Moreover, the oxidation peak current increased with an increased amount of glucose in the solution, which demonstrated that GOD/NGPs-modified GC electrode can electrocatalyze the oxidation of glucose using FMCA as mediator. The excellent electrocatalytic activity toward glucose oxidation might be useful for the development of GOD-based bioanode of BFC. Fig. 1C shows the CVs of laccase/NGPs-modified GC electrode in N2- and air-saturated 0.10 M pH 6.0 phosphate buffer containing 1.0 mM 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS). A pair of redox peaks of ABTS with formal potential of +0.455 V (vs. SCE) was observed in N2-saturated solution, but the reduction peak current increased obviously in air-saturated solution, which is typical electrocatalytic reduction of dioxygen to water by laccase. In contrast, no oxygen electrocatalysis reduction was observed for the NGPs-modified GC electrode in air-saturated solution with ABTS in the absence of laccase (black curve in Fig. 1C), since the cathodic peak currents and anodic peak currents were very similar. This result further indicated that ABTS can be used as redox mediator of electrocatalytic reduction of dioxygen to water by laccase. This electrocatalytic process in essence is that the oxidized laccase firstly oxidizes the ABTS, then the electroreduction of the enzymatically-generated ABTS•+ occurs as the oxidized state of ABTS [12]. On the other hand, a half-wave potential E1/2
W. Zheng et al. / Electrochemistry Communications 12 (2010) 869–871
871
the current density of glucose electro-oxidation was higher than that of oxygen electroreduction. Among them, the reached plateau indicated that the reaction was controlled by the mass transport diffusion of glucose and oxygen. The performance of NGPs-based glucose/O2 BFC was further investigated, as shown in Fig. 2B. The maximum power density of the BFC was ca. 57.8 μW cm− 2 at a cell voltage of 0.22 V, was larger than that of our previous work [4], but lower than that of Heller groups reported previously [3]. According to the polarization curves of Fig. 2A, it can be stated that the power output was limited by the electrocatalytic reduction of oxygen probably due to several factors such as the oxygen transformation to the interface of NGPs-modified GC electrode and the enzymatic activity of the laccase immobilized on the NGPs. In addition, the electrode shows a considerable loss of activity during the first 12 h, but then stabilizes. Although from the practical application point of view, the performance and the stability of the NGPs-based glucose/O2 BFC needs to be further improved, we believe that this initial demonstration can be useful for the development of novel kinds of carbon-based nanomaterial biosensors and biofuel cells. 4. Conclusions In this study, we had revealed the electrocatalytic glucose oxidation and dioxygen reduction on the NGPs-modified GC electrode, respectively. NGPs-based compartment-less glucose/O2 BFC with GOD and laccase as the anodic and cathodic biocatalysts were successfully assembled. The maximum power density of the BFC was ca. 57.8 μW cm− 2. In conclusion, NGPs demonstrate great useful potential for the future development of novel kinds of carbon-based nanomaterial biosensors and biofuel cells. Acknowledgements
Fig. 2. (A) Polarization curves obtained in a phosphate buffered solution for the bioanode GOD/NGPs-modified GC electrode in a 10 mM glucose solution (dashed line) and for the biocathode laccase/NGPs-modified GC electrode in air-saturated solution (solid line). (B) Polarization (○) and performance (●) curves of the assembled NGPsmodified GC electrode based glucose/O2 biofuel cell.
was +490 mV (vs. SCE), which was similar to the half-wave potentials of the catalytic currents produced by laccase in the presence of ABTS [7,13,14]. To demonstrate the possible potential application as the NGPs-based BFC, the as-prepared GOD/NGPs bioanode and the laccase/NGPs biocathode to form NGPs-based compartment glucose/O2 BFC had been assembled. It can be seen from Fig. 2A that the catalytic oxidation resulting from the glucose oxidation started at about +0.19 V (vs. SEC) and the electrocatalytic current on NGPs-based bioanode reached a plateau at 395 μA cm− 2. On the other hand, the electrocatalytic reduction current corresponding to the indirect reduction of dioxygen commenced from +0.55 V (vs. SEC) and reached a plateau at −155 μA cm− 2. Thus,
This work was supported by the National Natural Science Foundation of China (No. 20805010). References [1] X. Li, L. Zhang, L. Su, T. Ohsaka, L. Mao, Fuel cell 9 (2009) 85. [2] E. Katz, I. Willner, J. Am. Chem. Soc. 125 (2003) 6803. [3] T. Chen, S.C. Barton, G. Binyamin, Z. Gao, Y. Zhang, H.-H. Kim, A. Heller, J. Am. Chem. Soc. 123 (2001) 8630. [4] H.Y. Zhao, H.M. Zhou, J.X. Zhang, W. Zheng, Y.F. Zheng, Biosens. Bioelectron. 25 (2009) 463. [5] B.Z. Jang, A. Zhamu, J. Mater. Sci. 43 (2008) 5092. [6] S. Gilje, H. Song, M. Wang, K.L. Wang, R.B. Kaner, Nano Lett. 7 (2007) 3394. [7] W. Zheng, H.M. Zhou, Y.F. Zheng, N. Wang, Chem. Phys. Lett. 457 (2008) 381. [8] J. Yang, R. Zhang, Y. Xu, P. He, Y. Fang, Electrochem. Commun. 10 (2008) 1889. [9] K. Wang, H. Yang, L. Zhu, Z. Ma, S. Xing, Q. Lv, J. Liao, C. Liu, W. Xing, Electrochim. Acta 54 (2009) 4626. [10] S.J. Guo, S.J. Dong, Trends Anal. Chem. 28 (2009) 515. [11] Q. Sheng, K. Luo, J. Zheng, Bioelectrochemistry 74 (2009) 246. [12] P. Rowinski, R. Bilewicz, M.J. Stebe, E. Rogalska, Anal. Chem. 76 (2004) 283. [13] Y. Liu, X. Qu, H. Guo, H. Chen, B. Liu, S. Dong, Biosens. Bioelectron. 21 (2006) 2195. [14] V. Soukharev, N. Mano, A. Heller, J. Am. Chem. Soc. 126 (2004) 8368.
Contents lists available at ScienceDirect
Electrochemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e l e c o m
A glucose/O2 biofuel cell base on nanographene platelet-modified electrodes W. Zheng a, H.Y. Zhao a, J.X. Zhang a, H.M. Zhou a, X.X. Xu a, Y.F. Zheng a,b,⁎, Y.B. Wang b,c, Y. Cheng c, B.Z. Jang d a
Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001, China Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871, China c Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China d College of Engineering and Computer Science, Wright State University, 3640 Colonel Glenn Hwy., Dayton, OH 45435, USA b
a r t i c l e
i n f o
Article history: Received 22 March 2010 Received in revised form 8 April 2010 Accepted 9 April 2010 Available online 13 May 2010 Keywords: Biofuel cell Nanographene platelets Glucose oxidase Laccase
a b s t r a c t This study demonstrated a novel nanographene platelets (NGPs)-based glucose/O2 biofuel cell (BFC) with the glucose oxidase (GOD) as the anodic biocatalysts and the laccase as the cathodic biocatalysts. The GOD/ NGPs-modified electrode exhibited good catalytic activity towards glucose oxidation and the laccase/NGPsmodified electrode exhibited good catalytic activity towards O2 electroreduction. The maximum power density was ca. 57.8 μW cm− 2 for the assembled glucose/O2 NGPs-based BFC. These results indicated that the NGPs were very useful for the future development of novel carbon-based nanomaterials BFC device. © 2010 Elsevier B.V. All rights reserved.
1. Introduction
2. Experimental
The enzyme-based biofuel cell (BFC) is a special fuel cell using enzyme as catalyst and can directly convert chemical energy to electrical energy [1]. BFC has a potential application prospect due to its good biocompatibility and wide source of raw materials, which have attracted considerable research attention [1–3]. Some disadvantages such as deactivation, poor stability and low electron-transfer rate of enzyme become the bottleneck for the development of high quality BFC. In order to solve these problems, great efforts have been made by incorporating enzymes into appropriate matrix [4]. Nanoscale graphene platelet, consisting of nanometer-sized twodimensional graphene fragments with honeycomb lattice, is an emerging class of carbon-based nanomaterials [5]. In contrast to fulleren and carbon nanotube, NGPs have closed π-electron systems and feature as a twodimensional extended electronic structure of π-electrons with open edges. Thus it is considered as a rising star in carbon-based nanomaterial family for electrochemical applications [6]. In the present study, the NGPs were used as the matrix of anode catalyst GOD and cathode catalyst laccase, and the electrochemical performance of glucose/O2 BFC using NGPs as the substrates for both bioanode and biocathode was further investigated.
The fabrication details of NGPs can be found in our previous work [5]. The experimental NGPs were dried under vacuum at 100 °C for 24 h to remove the residual organic solvent prior to use. They were dispersed into aqueous solution to give a 2 mg mL− 1 homogeneous dispersion, then 8 µL of the dispersion was dip-coated onto the glassy carbon (GC) electrodes, followed by a period of standing in air until dry (denoted as NGPsmodified GC electrodes). The NGPs-modified GC electrodes were immersed into 10 mg mL− 1 glucose oxidase (GOD, Type X-S from Aspergillus niger, EC 1.1.3.4, 50 kU g− 1 solid) solution for 12 h, and then 2 µL of the Naifion solution (2 wt.%) was further introduced to form a tight membrane on the enzyme electrode. Laccase (E.C. 1.10.3.2, from Trametes versicolor, purchased from Fluka) was purified following the method reported previously by the present authors [7]. A 8 µL laccase–bovine serum albumin mixture (3/1 v/v) was spread evenly onto the NGPsmodified GC electrode and then cross-linked with 2µL glutaraldehyde (40 mM) onto the electrode, allowing the solution at the electrode to be dried up at an ambient temperature (denoted as laccase/NGPs-modified GC electrodes). All the electrochemical measurements were carried out using a computer-controlled electrochemical analyzer (CHI 650C, Chen-Hua, Shanghai). A conventional three-electrode cell was used, the modified electrodes as working electrodes, a platinum spiral wire as the counter electrode and a saturated calomel electrode (SCE) as the reference electrode. For the experiments conducted under anaerobic conditions, the electrolyte was bubbled with pure N2 for more than 30 min, and N2 was kept flowing over the solution during the electrochemical
⁎ Corresponding author. Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871, China. E-mail address: [email protected] (Y.F. Zheng). 1388-2481/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2010.04.006
870
W. Zheng et al. / Electrochemistry Communications 12 (2010) 869–871
measurements. For assembling an ascorbate/O2 biofuel cell, the GOD/ NGPs-modified electrode was used as the anode for the oxidation of glucose and the laccase/NGPs-modified electrode was used as the cathode for the O2 reduction. Nafion film was sandwiched as a separator
Fig. 1. (A) CVs of GOD/NGPs-modified GC (solid line) electrode at 100, 200, 300, 400, 500, 600, 700, 800 and 900 mV s− 1 (from inner to outer) and CVs of GOD/GC (dashed line) electrode at 100 mV s− 1 in air-saturated 0.10 M phosphate buffer. Inset showed a plot of cathodic and anodic peak currents against potential scan rate. (B) CVs of GOD/NGPsmodified GC electrodes in 0.10 M phosphate buffer solution containing 0.50 mM ferrocene monocarboxylic acid in the different concentrations of glucose. Scan rate: 10 mV s− 1. (C) CVs of laccase/NGPs-modified GC electrode in N2 (blue line) and air (red line), and CVs of NGPs-modified GC electrode in air (black line) saturated 0.10 M pH 6.0 phosphate buffer containing 1.0 mM ABTS. Scan rate: 10 mV s− 1. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
between two bioelectrodes. All electrochemical measurements were performed at least three times at 20± 2 °C. 3. Results and discussion Fig. 1A shows the CVs of the NGPs-modified GC electrode, GOD/ NGPs-modified GC electrode and GOD/GC electrode in 0.10 M phosphate buffer (pH 6.0) at a scan rate of 100 mV/s. No obvious redox peaks were observed for the GC electrode within the potential window (dashed line in Fig. 1A). However, a pair of well-defined quasi-reversible redox peaks was visible at −0.48 V and − 0.41 V (vs. SCE) for the GOD/NGPs-modified GC electrode (solid line in Fig. 1A). The separation of peak potentials and the formal potential were calculated to be ca. 70 mV and −0.445 V (vs. SCE), respectively, and corresponded to the electrode process of the FAD/FADH2 redox of the electroactive center of GOD [8]. As a control experiment, the electrochemistry of GOD at the GC electrodes was also studied and a pair of slight redox peaks was found (inset in Fig. 1A), but the peak currents were remarkably smaller than that obtained on the GOD/ NGPs-modified GC electrode, indicating that the presence of NGPs could facilitate the direct electron transfer of the GOD and enhance the electrochemical signal, which coincided well with the previous report [9]. It may be due to the fact that the large surface-to-volume ratio and high conductivity of NGPs could lead to the efficient realization of direct electron transfer between redox enzymes and the surface of electrode. NGPs in the sensing interface might act as an enhancing agent for effective acceleration of electron transfer between matrix and GOD, leading to more rapid current response for GOD [10]. In addition, the cathodic peak current was almost equal to the anodic peak current suggesting that the GOD adsorbed onto the surface underwent a reversible direct electrochemical reaction with two-electron transfer. Moreover, the cathodic and anodic peak currents (Ip) of the GOD increased with the increase of the scan rate (v) in the range from 100 to 900 mV s− 1, whereas the cathodic and anodic peak potentials exhibited a small shift, which was indicative of a fast electron-transfer rate. In order to confirm the enzymatic activity of the immobilized GOD on the NGPs-modified GC electrode, the electrocatalysis of GOD toward glucose was measured as shown in Fig. 1B. In the air-saturated phosphate buffer solution containing 0.50 mM ferrocene monocarboxylic acid (FMCA) as the mediator, a couple of well-defined redox peaks (black curve) appeared, corresponding to the redox reaction of FMCA [11]. When glucose was added into the buffers, the anodic peak current increased significantly at about +0.31 V (vs. SCE), accompanying with a decrease of the cathodic peak current. Moreover, the oxidation peak current increased with an increased amount of glucose in the solution, which demonstrated that GOD/NGPs-modified GC electrode can electrocatalyze the oxidation of glucose using FMCA as mediator. The excellent electrocatalytic activity toward glucose oxidation might be useful for the development of GOD-based bioanode of BFC. Fig. 1C shows the CVs of laccase/NGPs-modified GC electrode in N2- and air-saturated 0.10 M pH 6.0 phosphate buffer containing 1.0 mM 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS). A pair of redox peaks of ABTS with formal potential of +0.455 V (vs. SCE) was observed in N2-saturated solution, but the reduction peak current increased obviously in air-saturated solution, which is typical electrocatalytic reduction of dioxygen to water by laccase. In contrast, no oxygen electrocatalysis reduction was observed for the NGPs-modified GC electrode in air-saturated solution with ABTS in the absence of laccase (black curve in Fig. 1C), since the cathodic peak currents and anodic peak currents were very similar. This result further indicated that ABTS can be used as redox mediator of electrocatalytic reduction of dioxygen to water by laccase. This electrocatalytic process in essence is that the oxidized laccase firstly oxidizes the ABTS, then the electroreduction of the enzymatically-generated ABTS•+ occurs as the oxidized state of ABTS [12]. On the other hand, a half-wave potential E1/2
W. Zheng et al. / Electrochemistry Communications 12 (2010) 869–871
871
the current density of glucose electro-oxidation was higher than that of oxygen electroreduction. Among them, the reached plateau indicated that the reaction was controlled by the mass transport diffusion of glucose and oxygen. The performance of NGPs-based glucose/O2 BFC was further investigated, as shown in Fig. 2B. The maximum power density of the BFC was ca. 57.8 μW cm− 2 at a cell voltage of 0.22 V, was larger than that of our previous work [4], but lower than that of Heller groups reported previously [3]. According to the polarization curves of Fig. 2A, it can be stated that the power output was limited by the electrocatalytic reduction of oxygen probably due to several factors such as the oxygen transformation to the interface of NGPs-modified GC electrode and the enzymatic activity of the laccase immobilized on the NGPs. In addition, the electrode shows a considerable loss of activity during the first 12 h, but then stabilizes. Although from the practical application point of view, the performance and the stability of the NGPs-based glucose/O2 BFC needs to be further improved, we believe that this initial demonstration can be useful for the development of novel kinds of carbon-based nanomaterial biosensors and biofuel cells. 4. Conclusions In this study, we had revealed the electrocatalytic glucose oxidation and dioxygen reduction on the NGPs-modified GC electrode, respectively. NGPs-based compartment-less glucose/O2 BFC with GOD and laccase as the anodic and cathodic biocatalysts were successfully assembled. The maximum power density of the BFC was ca. 57.8 μW cm− 2. In conclusion, NGPs demonstrate great useful potential for the future development of novel kinds of carbon-based nanomaterial biosensors and biofuel cells. Acknowledgements
Fig. 2. (A) Polarization curves obtained in a phosphate buffered solution for the bioanode GOD/NGPs-modified GC electrode in a 10 mM glucose solution (dashed line) and for the biocathode laccase/NGPs-modified GC electrode in air-saturated solution (solid line). (B) Polarization (○) and performance (●) curves of the assembled NGPsmodified GC electrode based glucose/O2 biofuel cell.
was +490 mV (vs. SCE), which was similar to the half-wave potentials of the catalytic currents produced by laccase in the presence of ABTS [7,13,14]. To demonstrate the possible potential application as the NGPs-based BFC, the as-prepared GOD/NGPs bioanode and the laccase/NGPs biocathode to form NGPs-based compartment glucose/O2 BFC had been assembled. It can be seen from Fig. 2A that the catalytic oxidation resulting from the glucose oxidation started at about +0.19 V (vs. SEC) and the electrocatalytic current on NGPs-based bioanode reached a plateau at 395 μA cm− 2. On the other hand, the electrocatalytic reduction current corresponding to the indirect reduction of dioxygen commenced from +0.55 V (vs. SEC) and reached a plateau at −155 μA cm− 2. Thus,
This work was supported by the National Natural Science Foundation of China (No. 20805010). References [1] X. Li, L. Zhang, L. Su, T. Ohsaka, L. Mao, Fuel cell 9 (2009) 85. [2] E. Katz, I. Willner, J. Am. Chem. Soc. 125 (2003) 6803. [3] T. Chen, S.C. Barton, G. Binyamin, Z. Gao, Y. Zhang, H.-H. Kim, A. Heller, J. Am. Chem. Soc. 123 (2001) 8630. [4] H.Y. Zhao, H.M. Zhou, J.X. Zhang, W. Zheng, Y.F. Zheng, Biosens. Bioelectron. 25 (2009) 463. [5] B.Z. Jang, A. Zhamu, J. Mater. Sci. 43 (2008) 5092. [6] S. Gilje, H. Song, M. Wang, K.L. Wang, R.B. Kaner, Nano Lett. 7 (2007) 3394. [7] W. Zheng, H.M. Zhou, Y.F. Zheng, N. Wang, Chem. Phys. Lett. 457 (2008) 381. [8] J. Yang, R. Zhang, Y. Xu, P. He, Y. Fang, Electrochem. Commun. 10 (2008) 1889. [9] K. Wang, H. Yang, L. Zhu, Z. Ma, S. Xing, Q. Lv, J. Liao, C. Liu, W. Xing, Electrochim. Acta 54 (2009) 4626. [10] S.J. Guo, S.J. Dong, Trends Anal. Chem. 28 (2009) 515. [11] Q. Sheng, K. Luo, J. Zheng, Bioelectrochemistry 74 (2009) 246. [12] P. Rowinski, R. Bilewicz, M.J. Stebe, E. Rogalska, Anal. Chem. 76 (2004) 283. [13] Y. Liu, X. Qu, H. Guo, H. Chen, B. Liu, S. Dong, Biosens. Bioelectron. 21 (2006) 2195. [14] V. Soukharev, N. Mano, A. Heller, J. Am. Chem. Soc. 126 (2004) 8368.