Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 113-115).

This paper presents analytical and experimental studies on optimization of the gas delivery and current collection system in a proton exchange membrane (PEM) fuel cell for the objective of reducing ohmic loss, thereby achieving higher power density. Specifically, the dimensions of current collection ribs as well as the rib distribution were optimized to get a maximized power density in a fuel cell. In the modeling process, the power output from a fixed area of membrane is calculated through analysis of an electrical circuit simulating the current from electrochemical reaction flowing to the current collectors. Current collectors of two-dimensional ribs and three-dimensional pillars were considered. Analyses found that three-dimensional pillars allow higher power density in a PEM fuel cell. Considering the mass transfer enhancement effect, three-dimensional pillars as current collectors in gas flow field may be a good choice if the fuel cell operates at low current density and there is no liquid water blocking the flow channels. The analyses did not consider the existence of liquid water, meaning the current density is not very high. The study concluded that decreasing the size of both the current collector and its control area yields a significant benefit to a higher power density. A preliminary experimental test in a PEM fuel cell has verified the conclusion of the analytical work.

Two formal design methodologies, biomimetic design and the Theory of Inventive Problem Solving, TRIZ, were applied to the redesign of a Proton Exchange Membrane (PEM) fuel cell. Proof of concept prototyping was performed on two of the concepts for water management. The liquid water collection with strategically placed wicks concept demonstrated the potential benefits for a fuel cell. Conversely, the periodic flow direction reversal concepts might cause a potential reduction water removal from a fuel cell. The causes of this water removal reduction remain unclear. In additional, three of the concepts generated with biomimetic design were further studied and demonstrated to stimulate more creative ideas in the thermal and water management of fuel cells. The biomimetic design and the TRIZ methodologies were successfully applied to fuel cells and provided different perspectives to the redesign of fuel cells. The methodologies should continue to be used to improve fuel cells.

Two formal design methodologies, biomimetic design and the Theory of Inventive Problem Solving, TRIZ, were applied to the redesign of a Proton Exchange Membrane (PEM) fuel cell. Proof of concept prototyping was performed on two of the concepts for water management. The liquid water collection with strategically placed wicks concept demonstrated the potential benefits for a fuel cell. Conversely, the periodic flow direction reversal concepts might cause a potential reduction water removal from a fuel cell. The causes of this water removal reduction remain unclear. In additional, three of the concepts generated with biomimetic design were further studied and demonstrated to stimulate more creative ideas in the thermal and water management of fuel cells. The biomimetic design and the TRIZ methodologies were successfully applied to fuel cells and provided different perspectives to the redesign of fuel cells. The methodologies should continue to be used to improve fuel cells.

Submitted in the fulfillment of the requirements for the Master of Engineering, Durban University of Technology, Durban, South Africa. 2016. / The effectiveness of using a low cost non - platinum (Pt) material for the catalyst layer of a polymer electrolyte fuel cell (PEMFC) was investigated. A test cell and station was developed. Two commercial Pt loaded membrane electrode assemblies (MEA) and one custom MEA were purchased from the Fuelcelletc store. Hydrogen and oxygen were applied to either side of the custom MEA which resulted in an additional sample tested. An aluminium flow field plate with a hole type design was manufactured for the reactants to reach the reaction sites. End plates made from perspex where used to enclose the MEA, flow field plates, and also to provide reactant inlet and outlet connection points. The developed test station consisted of hydrogen and oxygen sources, pressure regulators, mass flow controllers, heating plate, and humidification units. A number of experimental tests were carried out to determine the performance of the test cells. These tests monitored the performance of the test cell under no-load and loaded conditions. The tests were done at 25 °C and 35 °C at a pressure of 0.5 bar and varying hydrogen and oxygen volume flow rates. The no-load test showed that the MEA’s performed best at high reactant flow rates of 95 ml/min for hydrogen and 38 ml/min for oxygen. MEA 1, 2, 3, and 4 achieved an open circuit voltage (OVC) of 0.936, 0.855, 0.486 and 0.34 V respectively. The maximum current density achieved for the MEAs were 0.3816, 0.284, 15x10-6, and 50x10-6 A/cm2. Under loaded conditions the maximum power densities achieved at 25 °C for MEA’s 1, 2, 3, and 4 were 0.05, 0.038, 2.3x10-6, 1.99x10-6 W/cm2 respectively. Increasing the temperature by 10°C for MEA 1, 2, 3, 4 resulted in a 16.6, 22.1, 1.79, 10.47 % increase in the maximum power density. It was found that increasing platinum loading, flow rates, and temperature improved the fuel cell performance. It was also found that the catalytic, stability and adsorption characteristics of silver did not improve when combining it with iridium (Ir) and ruthenium oxide (RuOx) which resulted in low current generation. The low maximum power density thus achieved at a reduced cost is not feasible. Thus further investigation into improving the catalytic requirements of non Pt based catalyst material combinations is required to achieve results comparable to that of a Pt based PEMFC. / M

Fuel cell technologies have developed high interest due to their ability to provide energy in an environmentally friendly method. Proton exchange membrane fuel cells (PEM-FCs) require a PEM for use, where the most accepted PEM used today is Nafion. Nafion is ideal due to its chemical durability and high proton conductivity however it is highly expensive and limited to 80˚C during operation. To target these issues two methods have been developed. One was to synthesize a new membrane material to replace Nafion based upon sulphonated polysiloxanes and the other was to improve Nafion by synthesizing a composite. Both of these methods involved the sulphonated silane 2-4-chlorosulphonylphenethyltrimethoxysilane. Methods to characterize membranes to observe their properties compared to Nafion were thermogravimetric analysis (TGA), Fourier transmission infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (used to determine proton conductivity) and fuel cell performance. / UOIT

Proton exchange membrane fuel cell (PEMFC) has been considered as one of the most promising energy conversion devices for the future in automotive applications. One of the major technical challenges for the commercialization of PEMFC is the effective start-up from subzero temperatures, often referred to as “cold start”. The major problem of PEMFC cold start is that the product water freezes when the temperature inside the PEMFC is lower than the freezing point. If the catalyst layer (CL) is fully occupied by ice before the cell temperature rises above the freezing point, the electrochemical reaction may stop due to the blockage of the reaction sites. However, only a few of the previous PEMFC studies paid attention to cold start. Hence, understanding the ice formation mechanisms and optimizing the design and operational strategies for PEMFC cold start are critically important. In this research, an experimental setup for the cold start testing with simultaneous measurement of current and temperature distributions is designed and built; a one-dimensional (1D) analytical model for quick estimate of purging durations before the cold start processes is formulated; and a comprehensive three-dimensional (3D) PEMFC cold start model is developed. The unique feature of the cold start experiment is the inclusion of the simultaneous measurement of current and temperature distributions. Since most of the previous numerical models are limited to either 1D or two-dimensional (2D) or 3D but only considering a section of the entire cell due to computational requirement, the measured distribution data are critically important to better understand the PEMFC cold start characteristics. With a full set of conservation equations, the 3D model comprehensively accounts for the various transport phenomena during the cold start processes. The unique feature of this model is the inclusion of: (i) the water freezing in the membrane electrolyte and its effects on the membrane conductivity; (ii) the non-equilibrium mass transfer between the water in the ionomer and the water (vapour, liquid and ice) in the pore region of the CL; and (iii) both the water freezing and melting in the CL and gas diffusion layer (GDL). This model therefore provides the fundamental framework for the future top-down multi-dimensional multiphase modelling of PEMFC. The experimental and numerical results elaborate the ice formation mechanisms and other important transport phenomena during the PEMFC cold start processes. The effects of the various cell designs, operating conditions and external heating methods on the cold start performance are studied. Independent tests are carried out to identify and optimize the important design and operational parameters.

Three aromatic poly(arylene ether)s P2¡BP3¡BP4 were synthesized from bis(fluoride)4,4¡¨¡¨-Difluoro-3,3¡¨¡¨-bsi-trifluoromethyl-n¡¨-bisphenyl-[1,1¡¦;4¡¦,1¡¨;4¡¨,1¡¨¡¦;4¡¨¡¦,1¡¨¡¨]-quinquephenyl(n¡¨:2¡¨,3¡¨[G2];2¡¨,3¡¨,5¡¨[G3];2¡¨,3¡¨,5¡¨,6¡¨[G4]) with 4,4'-(9-Fluorenylidene)diphenol. The molecular weight of the polymer (Mw: 105-1.6¡Ñ105, PDI:1.5-2.2) was measured by gel permeation chromatography and the structure was confirmed by NMR spectra. Thermal stability was measured using Thermogravimetry and Thermomechanical Analysis. The polymer had a Td at 520¢J ~550¢J, and soft point at 310¢J. Young's modulus of polymer was (1.25-2.5Gpa). This polymer has high strength, modulus of elasticity, and thermal stability. The polymer consists of polyaromatic groups with bisfluoride monomer, (5, 6, 7 aromatic). We hypothesized that sulfonation of the polymer will exhibit high conductivity and great mechanical properties. Ion exchange capacities (IECs) were evaluated by acid¡Vbase titration. We sulfonated the polymer in order to apply to the proton exchange membrane fuel cell. The results showed after sulfonation of P4, IEC is 3.3(meq/g), and sulfonation of P2 showed that its proton conductivity is 75% more than Nafion117 at 80¢J with 0.28(S/cm). Keywords: proton exchange membrane, proton conductivity, Nafion, sulfonated, ion exchange capacity

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This research is to develop procedures on the fabrication of membrane electrode assembly (MEA), which is the heart of the Proton Exchange Membrane Fuel Cell. Sensitivity studies of the manipulated variable, such as pressure, temperature, and time, in the hot press process, which is adopted in the assembling on the performance of the MEA are also performed. The developed products on the cleaning of membrane as well as the hot press of MEA have been verified through many experiments. The tests of the MEA¡¦s thus produced reveal that temperature and pressure in hot press process have significant influence on MEA performance. Both have to be kept in a suitable range. Optimal operating conditions in the hot press process may be achieved by conducting more experiments and a detail understanding on the internal structure variation of membrane under high pressure and temperature condition.