Sugar-powered fuel cells
10.1002/spepro.000051
Sugar-powered fuel cells Jongeun Ryu, Hak-Sung Kim, and H. Thomas Hahn
High-intensity light pulses provide a means of making nanoscale modifications to electrode surfaces that is fast, inexpensive, and green. Glucose is an abundant and renewable natural fuel, and it is safe and easy to handle and store. For these reasons, it is considered an ideal alternative fuel source for in vivo and portable electronic applications. However, glucose fuel cells are not readily available commercially. The main technological challenge posed by the devices is how to achieve high efficiency and long-term catalytic stability. Except for the obvious difference, glucose fuel cells work like their conventional hydrogen counterparts. In addition, noble metals such as platinum (Pt) are often used in the sugar-powered cells owing to their catalytic effect on glucose oxidation and relative stability compared with biological catalysts such as enzymes and microorganisms.1 To ensure high-power output per unit volume or unit mass, Pt catalysts and their supports require a high surface-to-volume ratio. For this reason, Pt nanoparticles and carbon nanotubes (CNTs) have attracted increasing attention.2 In general, CNTs are incorporated with Pt nanoparticles electrochemically3 and thermally.4 However, these chemical-based processes take a long time and cannot exploit the entire CNT surface area. Here we describe work aimed at developing new electrode materials for glucose fuel cells. Our approach employs a sputter deposition technique to make a thin Pt layer that takes full advantage of the large surface area of CNTs. We have also introduced a novel method of lightinduced modification of Pt structure to increase the active catalyst surface area. Intense pulsed light (IPL) was originally used in dermatological treatment. Our IPL system generates high-intensity light (20–50J/cm2 ) with short pulse duration (2–10ms). First, a thin Pt layer is sputtered onto the CNTs. The temperature of the Pt increases on IPL absorption, which results in formation of islands driven by surface energy diffusion of the Pt on the CNTs (see Figures 1 and 2). The second Pt layer is sputtered on the island-modified CNTs. The glucose oxidation activity of this electrode is compared to that of a standard electrode, on which the same amount of Pt is sputtered without IPL treatment. Cyclic voltammetry is used to characterize the catalytic activity. Three oxidation peaks (A, B, and C) appear during anodic scanning (see Figure 3). The peaks are attributed to dehydrogenation (A), oxidation of adsorbed intermediates such as carbon monoxide (B), and direct glucose oxidation on the cleaned Pt surface (C).5 The peak currents at
Figure 1. Scheme for structural modification of a catalyst layer by induced pulsed light (IPL)-assisted sputtering. CNT: Carbon nanotube.
Figure 2. Pt nanoisland formation on CNTs following IPL treatment.
Continued on next page
10.1002/spepro.000051 Page 2/2
Author Information Jongeun Ryu, Hak-Sung Kim, and H. Thomas Hahn Department of Mechanical and Aerospace Engineering University of California, Los Angeles (UCLA) Los Angeles, CA Jongeun Ryu has a PhD in mechanical engineering from UCLA. He received his MS and BS in mechanical engineering from the Korea Advanced Institute of Science and Technology. His research interests include nanomanufacturing and CNT applications such as fuel cells, batteries, and biosensors.
Figure 3. Current density-voltage profile of Pt-CNT electrodes in 0.5M glucose in 0.5M NaOH (sodium hydroxide): (a) nanoisland modified and (b) as sputtered. Scan rate: 10mV. Ag: Silver. AgCl: Silver chloride.
A, B, and C of the nanoisland-modified Pt-CNT electrode are 2.4, 1.8, and 1.8 times higher, respectively, than those of the standard electrode. Current density-voltage profiles show clearly that IPL surface treatment improves the electrocatalytic activity toward glucose. In summary, we are attempting to develop highly efficient, long-lived glucose fuel cells using nanoisland-modified Pt-CNT electrodes. Preliminary results have shown that devices based on this system generate power densities four times higher than those of the Pt-sputtered alternative. Furthermore, the IPL-assisted Pt-nanoisland formation process is shorter and less costly because it takes only milliseconds and does not consume chemicals. Our group is currently developing an IPL-assisted mass-manufacturing process for CNT applications.
Hak-Sung Kim received his PhD in mechanical engineering from the Korea Advanced Institute of Science and Technology in 2006. His current research focuses on reactive IPL for material synthesis in energyharvesting and storage applications such as solar cells, biofuel cells, and lithium-ion batteries. H. Thomas Hahn is the Raytheon Distinguished Professor with a joint appointment in the Materials Science and Engineering Department and the California NanoSystems Institute, UCLA. He also serves as editorin-chief of the Journal of Composite Materials. He has a PhD in engineering mechanics from the Pennsylvania State University. References 1. 1. S. Kerzenmacher, J. Ducree, R. Zengerle, and F. von Stetten, Energy harvesting by implantable abiotically catalyzed glucose fuel cells, J. Power Sources 182 (1), p. 1, 2008. doi:10.1016/j.jpowsour.2008.03.031 2. K. Lee, J. Zhang, H. Wang, and D. P. Wilkinson, Progress in the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for PEM fuel cell catalysis, J. Appl. Electrochem. 36 (5), p. 507, 2006. doi:10.1007/s10800-006-9120-4 3. Y. Zhao, L. Fan, H. Zhong, Y. Li, and S. Yang, Platinum nanoparticle clusters immobilized on multiwalled carbon nanotubes: electrodeposition and enhanced electrocatalytic activity for methanol oxidation, Adv. Funct. Mater. 17 (9), p. 1537, 2007. doi:10.1002/adfm.200600416 4. Y.-l. Yao, Y. Ding, L.-S. Ye, and X.-H. Xia, Two-step pyrolysis process to synthesize highly dispersed Pt-Ru/carbon nanotube catalysts for methanol electrooxidation, Carbon 44 (1), p. 62, 2006. doi:10.1016/j.carbon.2005.07.010 5. H.-W. Lei, B. Wu, C.-S. Cha, and H. Kita, Electro-oxidation of glucose on platinum in alkaline solution and selective oxidation in the presence of additives, J. Electroanal. Chem. 382 (1-2), p. 103, 1995. doi:10.1016/0022-0728(94)03673-Q
c 2009 Society of Plastics Engineers (SPE)
Sugar-powered fuel cells Jongeun Ryu, Hak-Sung Kim, and H. Thomas Hahn
High-intensity light pulses provide a means of making nanoscale modifications to electrode surfaces that is fast, inexpensive, and green. Glucose is an abundant and renewable natural fuel, and it is safe and easy to handle and store. For these reasons, it is considered an ideal alternative fuel source for in vivo and portable electronic applications. However, glucose fuel cells are not readily available commercially. The main technological challenge posed by the devices is how to achieve high efficiency and long-term catalytic stability. Except for the obvious difference, glucose fuel cells work like their conventional hydrogen counterparts. In addition, noble metals such as platinum (Pt) are often used in the sugar-powered cells owing to their catalytic effect on glucose oxidation and relative stability compared with biological catalysts such as enzymes and microorganisms.1 To ensure high-power output per unit volume or unit mass, Pt catalysts and their supports require a high surface-to-volume ratio. For this reason, Pt nanoparticles and carbon nanotubes (CNTs) have attracted increasing attention.2 In general, CNTs are incorporated with Pt nanoparticles electrochemically3 and thermally.4 However, these chemical-based processes take a long time and cannot exploit the entire CNT surface area. Here we describe work aimed at developing new electrode materials for glucose fuel cells. Our approach employs a sputter deposition technique to make a thin Pt layer that takes full advantage of the large surface area of CNTs. We have also introduced a novel method of lightinduced modification of Pt structure to increase the active catalyst surface area. Intense pulsed light (IPL) was originally used in dermatological treatment. Our IPL system generates high-intensity light (20–50J/cm2 ) with short pulse duration (2–10ms). First, a thin Pt layer is sputtered onto the CNTs. The temperature of the Pt increases on IPL absorption, which results in formation of islands driven by surface energy diffusion of the Pt on the CNTs (see Figures 1 and 2). The second Pt layer is sputtered on the island-modified CNTs. The glucose oxidation activity of this electrode is compared to that of a standard electrode, on which the same amount of Pt is sputtered without IPL treatment. Cyclic voltammetry is used to characterize the catalytic activity. Three oxidation peaks (A, B, and C) appear during anodic scanning (see Figure 3). The peaks are attributed to dehydrogenation (A), oxidation of adsorbed intermediates such as carbon monoxide (B), and direct glucose oxidation on the cleaned Pt surface (C).5 The peak currents at
Figure 1. Scheme for structural modification of a catalyst layer by induced pulsed light (IPL)-assisted sputtering. CNT: Carbon nanotube.
Figure 2. Pt nanoisland formation on CNTs following IPL treatment.
Continued on next page
10.1002/spepro.000051 Page 2/2
Author Information Jongeun Ryu, Hak-Sung Kim, and H. Thomas Hahn Department of Mechanical and Aerospace Engineering University of California, Los Angeles (UCLA) Los Angeles, CA Jongeun Ryu has a PhD in mechanical engineering from UCLA. He received his MS and BS in mechanical engineering from the Korea Advanced Institute of Science and Technology. His research interests include nanomanufacturing and CNT applications such as fuel cells, batteries, and biosensors.
Figure 3. Current density-voltage profile of Pt-CNT electrodes in 0.5M glucose in 0.5M NaOH (sodium hydroxide): (a) nanoisland modified and (b) as sputtered. Scan rate: 10mV. Ag: Silver. AgCl: Silver chloride.
A, B, and C of the nanoisland-modified Pt-CNT electrode are 2.4, 1.8, and 1.8 times higher, respectively, than those of the standard electrode. Current density-voltage profiles show clearly that IPL surface treatment improves the electrocatalytic activity toward glucose. In summary, we are attempting to develop highly efficient, long-lived glucose fuel cells using nanoisland-modified Pt-CNT electrodes. Preliminary results have shown that devices based on this system generate power densities four times higher than those of the Pt-sputtered alternative. Furthermore, the IPL-assisted Pt-nanoisland formation process is shorter and less costly because it takes only milliseconds and does not consume chemicals. Our group is currently developing an IPL-assisted mass-manufacturing process for CNT applications.
Hak-Sung Kim received his PhD in mechanical engineering from the Korea Advanced Institute of Science and Technology in 2006. His current research focuses on reactive IPL for material synthesis in energyharvesting and storage applications such as solar cells, biofuel cells, and lithium-ion batteries. H. Thomas Hahn is the Raytheon Distinguished Professor with a joint appointment in the Materials Science and Engineering Department and the California NanoSystems Institute, UCLA. He also serves as editorin-chief of the Journal of Composite Materials. He has a PhD in engineering mechanics from the Pennsylvania State University. References 1. 1. S. Kerzenmacher, J. Ducree, R. Zengerle, and F. von Stetten, Energy harvesting by implantable abiotically catalyzed glucose fuel cells, J. Power Sources 182 (1), p. 1, 2008. doi:10.1016/j.jpowsour.2008.03.031 2. K. Lee, J. Zhang, H. Wang, and D. P. Wilkinson, Progress in the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for PEM fuel cell catalysis, J. Appl. Electrochem. 36 (5), p. 507, 2006. doi:10.1007/s10800-006-9120-4 3. Y. Zhao, L. Fan, H. Zhong, Y. Li, and S. Yang, Platinum nanoparticle clusters immobilized on multiwalled carbon nanotubes: electrodeposition and enhanced electrocatalytic activity for methanol oxidation, Adv. Funct. Mater. 17 (9), p. 1537, 2007. doi:10.1002/adfm.200600416 4. Y.-l. Yao, Y. Ding, L.-S. Ye, and X.-H. Xia, Two-step pyrolysis process to synthesize highly dispersed Pt-Ru/carbon nanotube catalysts for methanol electrooxidation, Carbon 44 (1), p. 62, 2006. doi:10.1016/j.carbon.2005.07.010 5. H.-W. Lei, B. Wu, C.-S. Cha, and H. Kita, Electro-oxidation of glucose on platinum in alkaline solution and selective oxidation in the presence of additives, J. Electroanal. Chem. 382 (1-2), p. 103, 1995. doi:10.1016/0022-0728(94)03673-Q
c 2009 Society of Plastics Engineers (SPE)
