Browsing by Subject "Fuel cells"
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Item A basic model of hydrogen circulation in a proton exchange membrane (PEM) fuel cell(Texas Tech University, 1999-12) Akgerman, BoraThe fuel cell has come a long way since Sir Hubert Davy built the first prototype in 1801. After a slow 150 years, the fuel cell came to the attention of the world with the first slew of fuel cell operated vehicles in the 1950's. The next decade saw fuel cells used in NASA's Gemini and Apollo space missions. The 1990's have seen fuel cells in power plants, city busses, and space shuttle missions. Currently, $1 billion has been invested worldwide to investigate fuel cell operated vehicles as an alternate to Internal Combustion Engine (ICE) operated vehicles. With fuel cell efficiencies nearing 50%, low emissions and better reliability, fuel cell research is at an all-time high. This research will investigate the performance of the hydrogen circulation system of a Proton Exchange Membrane (PEM) fuel cell specifically designed for a hybrid vehicle. System parameters will be analyzed to find the optimum operating conditions for the hydrogen circulation system.Item A model for analyzing the experimental voltage-current characteristics of a hydrogen-oxyen fuel cell battery(Texas Tech University, 1969-05) Epps, Clift MooreNOT AVAILABLEItem Activity of methanol electro-oxidation at PtRu materials at temperatures in the range of 23°C to 70°C(Texas Tech University, 2004-05) Xu, ShanhongThe electrochemical oxidation of 0.5 M methanol in 0.1 M HCIO4 on catalyst materials comprised of platinum and ruthenium (PtRu) was investigated. Cyclic voltammetry and constant potential amperometry were used to characterize the catalyst materials and study the methanol reaction kinetics. Measurements were performed at temperature in the range of 23°C to 70°C. The following catalyst materials were employed: PtRu black containing 50 at. % Ru supplied by Johnson Matthey of Ward Hill. MA (JM PtRu black); sonochemically prepared nanoparticles of PtRu containing either 50 at. % Ru (SC PtRu(50)) or 25 at. % Ru (SC PtRu(25)); and Pt black (supplied by Johnson Matthey) modified by spontaneous deposition of Ru via either two (JM Pt-Ru(2)) or four deposition cycles (JM Pt-Ru(4)). The rate of methanol oxidation was assessed through constant potential amperometry measurements. Current was recorded 20 min after stepping to the reaction potential. Mechanistic information was derived from Tafel plots (plot of the logarithm of the current versus the reaction potential).Item An electrochemical and spectroscopic investigation into carbon monoxide surface poisoning(Texas Tech University, 2000-05) Kardash Richardson, Dawn Jo-ElleAn electrochemical cell was constructed that allows surface infrared spectroscopy measurements to be made in situ at temperatures relevant to the operation of direct methanol fuel cells (ambient to 80°C). The cell was used to investigate temperature effects on the electrochemistry of water, CO and methanol at bulk Pt and Pt-Ru electrodes in 0.1 M HCIO4. Initially, the surface chemistry of CO on a polycrystalline Pt electrode was studied. An Adiayer of CO at saturation coverage was stable over a period of five hours in the range of 25 °C-50 °C. Above 60 °C, the adiayer became unstable. In the absence of CO in solution, only low CO coverages could be sustained between 60 °C and the high temperature limit of the experiments (75 °C). However, with CO or a source of CO such as methanol in solution, high CO coverages were sustained up to 75°C. In measurements of CO oxidation, the onset potential for the conversion of CO to CO2 decreased by 50 mV when the temperature was increased from 25 °C to 75 °C. In contrast, adsorbed CO formed through the dissociative chemisorption of methanol (1.5 x 10'^-1.0 M) was more oxidation resistant between 50 °C-75 °C. The in situ spectroscopic measurements provide molecular level evidence that the thermal activation of water dissociation can decrease the steady-state coverage of surface poisons and thereby increase the rate of methanol oxidation on Pt electrodes. In final studies, the surface chemistry of 0.1 M methanol on two bulk Pt-Ru alloy electrodes (10 atomic % Ru and 90 atomic % Ru) was investigated at 25 °C - 80 °C. High CO coverages were sustained on both alloys at all temperatures. However, CO2 evolved rapidly from CO covered surfaces above 0.4 V-0.5 V, suggesting that CO formed during methanol oxidation is more reactive and transient on the alloys than on Pt. The experiments reported in the dissertation provide a foundation for the in situ study of fuel cell reactions on new catalyst preparations with FTIR spectroscopy.Item Auxiliary power system for HEV(Texas Tech University, 2000-05) Alam, Md. ShahedulDriving the automobiles with a power generating unit other than an IC Engine is one of the main focus areas of present day Advanced Vehicle Engineering research. In this regard, the use of a fuel cell in combination with a power converter and motor as an alternative to the IC Engine as the primary power source for an automobile is very attractive. This thesis develops model of a series hybrid vehicle with a PEM fuel cell as its Auxiliary Power Unit (APU). Simulation using the model helps to provide an understanding of the interaction and flow of power. Moreover, electrical power sharing between the APU and the Electrical Storage System (ESS) is shown. Conclusions and scope of future work are also discussed.Item Cathode catalysts for low-temperature fuel cells : analysis of surface phenomena(2013-12) Mathew, Preethi; Manthiram, Arumugam; Goodenough, John B.The electrochemical oxygen reduction reaction (ORR) steps on a noble metal catalyst in an acidic aqueous electrolyte depend on the nature of the catalytic surface with which the O₂ molecule interacts. It has been assumed that the O₂ molecules interact directly with a bare noble-metal surface. By studying the nature of chemisorbed species on the surface of a metal catalyst as a function of the voltage on the anodic and cathodic sweeps, it is shown here that the O₂ reacts with a surface covered with oxide species extracted from the aqueous electrolyte and not from the O₂ molecules; the ORR is more active when the surface species are OH rather than O. Moreover, the strength of the chemical bond of the adsorbed species was shown to depend on the relative strengths of the metal-metal versus metal-oxide bonds. The Pt-Pt bonds are stronger than the Pd-Pd bonds, and the relative Pd-O bonds are stronger than the relative Pt-O bonds. As a result, the chemisorbed O species is stable to lower anodic potentials on Pd. CO oxidation to CO₂ occurs at a higher potential on Pd than on Pt, which is why Pd (not Pt) is tolerant to methanol. Experiments with alloys show the following: (1) methanol tolerance decreases with the increase of Pt in the Pd-Pt alloys with Pd₃Pt/C showing an initial tolerance that decreases with cycling; (2) OH is formed on Pt₃Co/C and core-shell Pt-Cu/C, which results in a higher activity and durability for the ORR on these catalysts; (3) a 300°C anneal is needed to stabilize the Pd₃Au/C catalyst that forms an O adsorbate; and (4) OH is formed on Pd₃Co/C and Pd₃CoNi/C. These studies provide a perspective on possible pathways of the ORR on oxide-coated noble-metal alloy catalysts.Item Development of alternative cathodes for intermediate temperature solid oxide fuel cells(2009-08) Kim, Junghyun; Manthiram, ArumugamItem Development of anode catalysts for direct alcohol fuel cells(2010-08) Lee, Eungje; Manthiram, Arumugam; Goodenough, John B.; Bard, Allen J.; Ferreira, Paulo; Meyers, Jeremy P.Direct alcohol fuel cells (DAFC) are attracting considerable interest to meet a variety of energy needs as they offer higher efficiency with less pollution compared to other conventional energy-conversion devices. However, the sluggish alcohol oxidation reaction kinetics and durability problems of the conventional Pt-Ru anode catalyst hamper the commercialization of the DAFC systems. With an aim to overcome these problems, there have been intensive efforts to alloy Pt-Ru with other metals. Although such strategies have led to some enhancement in activity, the durability problem caused by the instability of Ru could still not be alleviated. In this regard, this dissertation focuses on the development of non-Ru electrocatalysts with high activity and durability for DAFC applications. First, Ru-free, Pt-based bimetallic electrocatalysts for methanol oxidation reaction (MOR) were studied. Particularly, Pt-Sn and Pt-CeO₂ catalysts were synthesized, respectively, by a polyol method and a one-step reverse microemulsion (RME) method. The prepared samples are investigated for phase and morphological evaluations by various material-characterization techniques. Cyclic voltammetry and accelerated durability tests revealed that these alternative catalysts have much higher stability with a catalytic activity for MOR comparable to that of Pt-Ru. In the case of Pt-CeO₂, an improved particle morphology is obtained by the RME synthesis, and the advantage of the RME method is reflected by a higher catalytic activity in comparison to that of Pt-CeO₂ synthesized by the conventional synthesis method. It has been known that Pt-Sn is better than Pt-Ru for ethanol oxidation reaction (EOR), and the direct ethanol fuel cells (DEFC) employing Pt-Sn as the anode catalyst have better durability than the DMFC system employing a Pt-Ru anode catalyst. Therefore, this dissertation then focused on the enhancement of the catalytic activity for EOR by incorporating a third metal M to the Pt-Sn catalyst. Following the synthesis and characterization of the Pt-Sn-M (M = Mo and Pd) alloys, the effect of M on the enhanced catalytic activity of Pt-Sn-M is presented. The activity enhancement of the above catalysts is based on the promoting effect of the second or third elements added to Pt. However, in the final chapter of this dissertation, the activity enhancement of Pt nanoparticle itself through the formation of low energy surfaces is investigated. Carbon-supported Pt nanoparticles are synthesized in mixed water-ethylene glycol solvent, and the positive effect of the mixed solvent on both the morphology and surface structure of the Pt nanoparticles for COad oxidation is discussed.Item Dynamic modeling and analysis of proton exchange membrane fuel cells for control design(2016-05) Headley, Alexander John; Chen, Dongmei, Ph. D.; Wei, Li; Beaman, Joseph J; Ezekoye, Ofodike A; Mullins, Charles BThis dissertation seeks to address a number of issues facing the advancement of Proton Exchange Membrane (PEM) fuel cell technology by improving control-oriented modeling strategies for these systems. Real-time control is a major ongoing challenge for PEM fuel cell technologies, particularly with regards to water and temperature dynamics. This can lead to a number of operational concerns, such as membrane flooding and dehydration, which can seriously diminish the efficiency, reliability, and long term health of the system. To combat these issues, comprehensive models that are capable of capturing the dynamics of the key operating conditions and can be processed in real time are needed. Also, given the inherently distributed nature of the system, such a model would ideally account for the changes in the conditions from cell-to-cell in the stack, which can be very significant. With this goal in mind, the main focus of this dissertation is the development and experimental validation of control-oriented modeling techniques for PEM fuel cell stacks. The first major work in this study was the verification of a relative humidity model in response to varying loads. Through this work, a multiple control volume (CV) approach was developed and experimentally validated to model the distribution of operating conditions more accurately while keeping the computational expense sufficiently low. To optimize the modeling efforts, further analysis of the temperature and vapor distribution was performed starting from first principles. This led to the creation of various techniques to optimally size CVs based on the parameters and operating conditions of the system in question. Finally, it was noted throughout the testing that the performance of the membrane electrolyte assemblies in the test stack declined significantly from their initial state. To compensate for this, a Kalman filter was implemented to quantify the membrane degradation. SEM analysis of membranes from the test stack confirmed the validity of this technique. This work can be used to significantly improve real-time models for PEM fuel cells for model-based control applications.Item Effect of anode properties on the performance of a direct methanol fuel cell(2010-12) Garvin, Joshua Joseph; Meyers, Jeremy P.; Hidrovo, CarlosThis thesis is an investigation of the anode of a direct methanol fuel cell (DMFC) through numerical modeling and simulation. This model attempts to help better understand the two phase flow phenomena in the anode as well as to explain some of the many problems on the anode side of a DMFC and show how changing some of the anode side properties could alleviate these problems. This type of modeling is important for designing and optimizing the DMFC for specific applications like portable electronics. Understanding the losses within the DMFC like removable of carbon dioxide, conversion losses, and methanol crossover from the anode to the cathode will help the DMFC become more commercially viable. The model is based on two phase flow in porous media combined with equilibrium between phases in a porous media with contributions from a capillary pressure difference. The effect of the physical parameters of the fuel cell like the thickness, permeability, and contact angle as well as the operating conditions like the temperature and methanol feed concentration, have on the performance of the DMFC during operation will be investigated. This will show how to remove the gas phase from the anode while enabling methanol to reach the catalyst layer and minimizing methanol crossover.Item Electrochemical and transmission infrared spectroscopic studies of methanol oxidation reactions at platinum and platinum-ruthenium fuel cell catalysts(Texas Tech University, 2003-05) Gao, LinThis thesis describes an ex situ approach using a micro-volume infrared transmission flow cell for quantitative determinations of CO2 dissolved in solutions following electrochemical oxidation reactions. Based on this novel technique, the investigation of the activity of electrodes toward methanol oxidation to CO2 is reported. As an in situ probe, infrared spectroscopy is quite sensitive to CO2 formation from electrochemical oxidation pathways of fuel cells. However, quantification of CO2 is made difficult by the optical properties of infrared spectroelectrochemical cells. The ex situ method demonstrated here provides CO: quantities, percent yields and formation rates, and probably a more accurate determination of the relationship between applied potential and CO2 formation rate compared to in situ infrared spectroscopy methods. Initially, the formation of CO2 from 0.1 M formic acid electrochemical oxidation was studied. The average yields of CO2 are close to 100 % across the range of potentials studied. The experimental results demonstrate the ex situ technique has sufficient sensitivity to determine CO2 in electrolyzed samples following 180 s reaction time, and also provides the ability to make repetitive measurements simply and rapidly. Most work focuses on the formation of CO2 from 1.0 M methanol electrochemical oxidation on supported Pt and Pt-Ru catalysts on catalytically inert gold. Pt black, Pt-Ru black catalysts and Vulcan XC-72R carbon supported R and R-Ru catalysts have been considered. The rate of CO2 production increased as potential was made more positive up to 0.9 V (vs. a KCI saturated Ag/AgCI reference electrode). The CO2 yields decreased at lower potentials, as partially oxidized species adsorbed onto the catalyst surface. Methanol oxidation has resulted in above 80 % CO2 yields on Pt-Ru catalysts at all potentials between 0.2 V and 0.7 V; and 60-80 % CO2 yields at potentials between 0.6 V and 0.9 V and 40-60 % CO2 yields at potentials between 0.4 V and 0.5 V on Pt catalysts. The lower CO2 yields in the pure R case, which indicated incomplete methanol oxidation, are predictably ascribed to more evident adsorption of partial oxidation products and larger formation of soluble intermediates. Under the conditions studied. R-Ru based nano-cluster electro-catalysts provide the greatest activity for the electrochemical oxidation of methanol.Item Evaluating the power capabilities of a hydrogen fuel cell(Texas Tech University, 1999-05) Turner, Wallace D. L.The hydrogen fuel cell has become a very important dc source that has many applications including transportation, power stations, and space missions. The voltage per cell is limited, however, the current density per surface area is very large. So, very high power can be produced from a fuel cell with a low voltage. This thesis describes testing done on a solid polymer proton exchange membrane fuel cell that produces 1 volt maximum per cell with 300A test maximum load. The focus of this report deals with evaluating the power capabilities and characteristics of the 4 cell stack using a test stand. In this effort, it is possible to understand the implications of implementing a one hundred, and ten cells stack into an automobile.Item Fabrication of PEM fuel cell bipolar plate by indirect selective laser sintering(2006) Chen, Ssuwei; Bourell, David LeeItem Formaldehyde yields from methanol electrochemical oxidation on platinum and supported catalysts(Texas Tech University, 1999-12) Childers, Christina L.The formation of formaldehyde during methanol electrochemical oxidation is being measured with a fluorescence assay in order to assess the importance of formaldehyde as a reaction intermediate and source of efficiency loss in direct methanol fuel cells. Initial studies have focused on the oxidation of methanol on polycrystalline platinum. The formaldehyde yields approached 30% of the total electrolysis charge at 0.2-0.3 V (vs. a KCI saturated Ag/AgCI reference electrode) for methanol concentrations between 15 mM and 0.3 M in 0.1 M perchloric acid. The formaldehyde yields were lower at more positive potentials, as other oxidation pathways became dominant. However, the rate of formaldehyde production increased up to 0.5 V. These initial studies have demonstrated that formaldehyde, which is often not detectable with modern in situ spectroelectrochemical analysis techniques, can be produced in significant amounts during methanol electrochemical oxidation. More recent work has focused on the formation of formaldehyde during methanol electrochemical oxidation on supported platinum and platinumruthenium catalysts. Solid, polycrystalline platinum-ruthenium alloys have been considered. Other catalysts studied have been suspended in Nafion and supported on glassy carbon. Methanol oxidation on the catalysts has resulted in low formaldehyde yields, below 2% at all potentials studied. The low formaldehyde yields, which result from more complete methanol oxidation, are believed to arise from the ability of partial oxidation products to be transported to an array of active catalyst sites dispersed within the three dimensional Nafion film network. Efforts to eliminate these volume effects through techniques such as electrochemical depositions of catalyst crystallites by reduction of transition metal salts onto solid, glassy carbon electrodes; direct metal nanoparticle deposition onto solid, glassy carbon electrodes using a hydrogen tube furnace; and "sticky" carbon methods for metal/wax/carbon type electrodes have been under investigation.Item Laser sintering for high electrical conduction applications(2012-05) Murugesan Chakravarthy, Kumaran; Bourell, David Lee; Manthiram, Arumugam; Meyers, Jeremy P.; Beaman, Joseph J.; Juenger, Maria G.Applications involving high electrical conduction require complex components that are difficult to be manufactured by conventional processes. Laser sintering (LS) is an additive manufacturing technique that overcomes these drawbacks by offering design flexibility. This study focuses upon optimizing the process of laser sintering to manufacture functional prototypes of components used in high electrical conduction applications. Specifically, components for two systems – high current sliding electrical contacts and fuel cells – were designed, manufactured and tested. C-asperity rails were made by LS and tested in a high current sliding electrical setup. Corrugated flow field plates were created by LS and their performance in a direct methanol fuel cell (DMFC) was tested. This is the first experimental attempt at using laser sintering for manufacturing such complex components for use in high electrical conduction applications. The second part of this study involves optimization the laser sintering process. Towards this, efforts were made to improve the green strength of parts made by LS. Particle size of graphite/ phenolic resin and addition of nylon/11 and wax were tested for their effect upon green strength. Of these, significant improvement of green strength was observed by altering the particle size of the graphite/ phenolic resin system. New methods of improving green strength by employing fast cure phenolic resins with carbon fiber additions were successfully demonstrated. This study also identified a binder system and process parameters for indirect LS of stainless steel –for bipolar plate compression/ injection mold tooling. All the experimental results of this study lead us to believe that laser sintering can be developed as a robust and efficient process for the manufacture of specialized components used in advanced electrical conduction systems.Item Modeling of a fuel cell(Texas Tech University, 2002-08) Maroju, PraveenThe development of alternates to the internal combustion (IC) engine is widespread these days. Electric vehicles and hybrid electric vehicles are promising alternatives to the IC engine. Electric vehicles are completely battery operated while HEVs consists of at least one auxiliary source of electrical energy that drives a set of motors, apart from the battery. Proton exchange membrane fuel cell is one such auxiliary source. This thesis is focused on developing a simple model for the proton exchange membrane hydrogen-oxygen fuel cell. This report deals with the theory behind the fuel cell from electrochemical, thermodynamic and mathematical point of view. And documents the simple model of the fuel cell developed using Simulink®. This is followed by a detailed analysis of this model and comparison with the practical fuel cell.Item On-board hydrogen production for fuel cell vehicles via a membrane separator and an externally-fired methanol reformer(Texas Tech University, 2004-05) Mathakari, Sushil PrakashMany options exist for on-board hydrogen production from liquid fuels for fuel cell powered vehicles. This paper reports on design and construction of an on-board system for hydrogen production from methanol. Methanol reforming is accomplished using an externally fired catalytic reactor. Carbon monoxide, separated from the reactor effluent by a membrane separator, is consumed with the reactor fuel. The reactor is operated at 1950 kPa to supply gas to the membrane separator at its maximum design pressure, and at a temperature of 500°C, to minimize the amount of methanol remaining the reactor product. The design methanol feed rate of 0.32 1/min used for the prototype should be sufficient to supply a 10 kW fuel cell package, but the design can easily be expanded to larger sizes. The membrane separator is an off-the-shelf, polymer-based model, and it is not expected to reduce the carbon monoxide to below 10 ppm, required by proton exchange membrane fuel cells, being considered for vehicular power. For this reason it is necessary to include a selective oxidation reactor to remove the carbon monoxide as a contaminant. An adiabatic energy balance indicates that 30% excess energy is available from combustion of the separated carbon monoxide when used as fuel to the reformer. The thesis includes the design of methanol reformer system, calculation of heat transfer coefficients and heat transfer areas required for the heat exchange of the exhaust gases and the reaction mixture. It also includes the simulation of the entire process using ChemCAD as a chemical process simulator.Item Simulation, analysis, and mass-transport optimization in PEMFCs(2011-12) Olapade, Peter Ojo; Meyers, Jeremy P.In this dissertation, we present two major lines of numerical investigation based on a control-volume approach to solve coupled, nonlinear differential equations. The first model is developed to provide better understanding of the water management in PEMFC operating at less than 100ºC, under transient conditions. The model provides explanations for the observed differences between hydration and dehydration time constants during load change. When there is liquid water at the cathode catalyst layer, the time constant of the water content in the membrane is closely tied to that of liquid water saturation in the cathode catalyst layer, as the vapor is already saturated. The water content in the membrane will not reach steady state as long as the liquid water flow in the cathode catalyst layer is not at steady state. The second model is to optimize the morphological properties of HT-PEMFCs components so as to keep water generated as close as possible to the membrane to help reduce ionic resistance and thereby increase cell performance. Humidification of the feed gas at room temperature is shown to have minimal effects on the ionic resistance of the membrane used in the HT-PEMFC. Feed gases must be humidified at higher temperature to have effects on the ionic resistance. However, humidification at such higher temperatures will require complex system design and additional power consumption. It is, therefore, important to keep the water generated by the electrochemical reaction as close as possible to the membrane to hydration the membrane so as to reduce the ionic resistance and thereby increase cell performance. The use of cathode MPL helps keep the water generated close to the membrane and decreasing the MPL porosity and pore size will increase the effectiveness of the MPL in keep the water generated close to the membrane. The optimum value of the MPL porosity depends on the operating conditions of the cell. Similarly, decreasing the GDL porosity helps keep water close to the membrane and the optimum value of the GDL porosity depends on the operating conditions of the cell.Item Studies on electrochemical reaction pathways of methanol electro oxidation on nanoscale fuel cell catalysts(Texas Tech University, 2004-05) Vijayaraghavan, GaneshIn situ infrared spectroscopy and cyclic voltammetry were used to study the electrochemical reaction pathways of methanol oxidation on nanoscale carbon supported platinum (C/Pt, 10% Pt) and platinum ruthenium (C/PtRu, 30% Pt, 15% Ru) fuel cell catalysts. A temperature controlled electrochemical cell and electrodes that contained a built-in temperature sensor were utilized to probe surface electrochemistry of the catalysts from ambient temperatures to 70° C. Initial experiments were conducted on bulk Pt to help interpret results in experiments with nanocatalysts. Methanol dissociative adsorption studies on bulk Pt in 0.1 M HCIO4 and 0.1 M 13CHsOH in 0.1 M HCIO4 helped attribute bands from 2065-2080 cm"^ to C-0 stretching modes of CO molecules coordinated to single Pt atoms in an atop coordination arrangement. An increase in band intensity was observed when potentials (reported in volts measured with respect to a reversible hydrogen electrode, VRHE) were stepped positive up to 0.5 VRHE. These intensities began to diminish when potentials approached the oxidation levels for CO to CO2 above 0.5 VRHE- Catalyst inactivation data derived from the experiments on bulk Pt directed research into probing surface electrochemistry of methanol oxidation on the nanoscale catalysts. Formic acid and methanol electro oxidation studies were carried out on the C/Pt and C/PtRu nanocatalysts from ambient to 70° C. The C/Pt 10% loading catalyst was not as active as bulk Pt, as indicated by a comparison of current densities for methanol oxidation at 60° C and by temperature dependent shifts in the oxidation potential for rapid methanol oxidation. Greater attention to thermal and electrochemical pretreatment of the nanoscale catalyst, in order to remove surface contamination would likely help to increase nanocatalyst activity. Experiments on the PtRu nanoscale catalysts show that they had comparable behavior as that of their bulk counterparts. The PtRu nanocatalysts were more active for CO2 formation than bulk PtRu or C/Pt, but adsorbed CO on the catalyst surface was difficult to probe. Pretreatment procedures and inherent surface properties of C/PtRu are expected to affect electrochemical responses for methanol oxidation compared to bulk materials. A better understanding of fuel cell catalysts can help speed up the commercialization of direct methanol fuel cells.Item Synthesis and characterization of carbon nanotube supported nanoparticles for catalysis(2007-12) Vijayaraghavan, Ganesh, 1978-; Stevenson, Keith J.This dissertation describes the synthesis and characterization of nitrogen doped carbon nanotube (NCNT) supported nanoparticles for catalysis, specifically, the cathodic oxygen reduction reaction (ORR) in fuel cells. Strategies for synthesis of mono- and bimetallic nanoparticle catalysts through dendrimer based templating techniques and with the aid of metal organic chemical vapor deposition (MOCVD) precursors and efficient assembly protocols of the catalysts with the NCNTs are discussed in detail. Physicochemical properties of the NCNTs and NCNT supported catalysts were characterized using a host of tools including scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), thermo gravimetric analysis, BET surface area and pore size analysis and electrochemical techniques including cyclic voltammetry, chronocoulometry, chronoamperometry and rotating disk electrode voltammetry. Chapter 1 serves as a general introduction and provides a brief overview of challenges associated with the synthesis, characterization and utilization of graphitic carbons and graphitic carbon supported catalysts in heterogeneous catalysis. Chapter 2 provides an overview of the synthesis and characterization of systematically doped iron and nickel catalyzed NCNTs in an effort to understand the effect of nitrogen doping on ORR. Chapter 3 describes the use of NCNTs as supports for dendrimer templated nanoparticle catalysts for ORR. A facile synthetic strategy for the immersion based loading of catalysts onto NCNTs by spontaneous adsorption to achieve specific catalyst loadings is explored. Chapter 4 details the loading of monodisperse Pt, Pd and PtPd catalysts on the as synthesized NCNTs using MOCVD precursors. The MOCVD route offers promise for direct dispersion and activation of ORR catalysts on NCNT supports and eliminates a host of problems associated with traditional solvent based catalyst preparation schemes. Chapter 5 details future directions on a few topics of interest including efficient electrodeposition strategies for preparing NCNT supported catalysts, studies on PtCu catalysts for ORR and finally prospects of using NCNT supported catalysts in fuel cell applications.