Proton Exchange Membrane Materials for Fuel Cells - Annotated Bibliography Example

Proton Exchange Membrane Materials for Fuel Cells Proton Exchange Membrane Materials for Fuel Cells Introduction Proton Exchange Membrane Fuel Cells (PEMFC) or Polymer Electrolyte Membrane Fuel Cells have become the most promising clean-energy technology being developed (Vishnyakov, 2006). Research on PEMFC started from early 1960’s, and the technique has been continuously developing and being applied in numerous areas. The PEM fuel-cells produce electric energy from electrode reaction of hydrogen fuel and oxidant. PEMFC comprises hydrogen anode, oxygen cathode and proton exchange membrane, the function of it works as the reverse reaction of water electrolysis (Zaidi, 2009). Anode: 2H2→ 4H+ +4e- Cathode: O2+4H++4e-→2H2O The key selling position of PEMFC technology is their superior energy-conversion effectiveness compared to other fuel cells like AFC, PAFC or MCFC. For instance, it has been found this can go up to 60% efficiency under favorable conditions (Vishnyakov, 2006). Due to PEMFC high energy conversion it is able to start at low temperature quickly, be used for diverse power needs, in addition to having low radiation, emission and noise pollution. Hence, proton exchange membrane fuel cells can became useful in electricity power generation more than hydroelectric power or thermal power generation. However, low temperature PEM fuel cells have various disadvantages, and which in the end reduce the efficiency of the membrane. This includes carbon monoxide catalyst poisoning, high technology costs, humidification, and poor heat management (Bose & et tal, 2011). Applications of PEMFC could in laptop, military communication power source, and vehicle power (Zaidi, 2009). Ballard Power Systems which is a Canadian firm supports PEMFC technique for Benz and Ford on their electro mobile cars. In 1993, the first PEMFC “Green automobile” was invented by an American firm Energy Partner, and the car has 15KW power, 60m/h max speed while being able to be driven 96Km after every charge. In addition, Hwang Company of China released PEMFC Electric Bicycle in 2004, and such developments have enabled PEMFC to be applied in crucial fixed power source. Therefore, the heat generated from PEM fuel cells is possible to be utilized for heat supply. Also, long life of the PEM fuel cells gives an opportunity to power on next generation space vehicle like Helios which is being produced by NASA (Loyselle & Prokopius, 2011). Although PEMFC has successes on some other areas, there are still many problems that need to be resolved. In particular, high temperature PEMFCs operating in the range of 1000 C to 2000 C, faces numerous technical shortcomings during the normal elevated temperature treatments of their polymer-electrolyte membranes (Vishnyakov, 2006). Furthermore, just after startup of PEM fuel cells, the reagent gas can on most instances bring some pollution, like CO, sulfide and which might dump and obstruct reactions. Since the reactions generate enormous amount of water and heat, it is crucial to design how to protect the cells from such pollutants so as to work in a stable manner, and this is what is putting scientists’ minds busy. From the technical perspective, searching better catalytic materials and method to collect and amass hydrogen are the challenges that scientists have to face. Hence, the aim of this paper is to evaluate the development of PEMFC, including the challenges such as high cost of technology and polymer treatment. Annotated Bibliography Alberti, G., & Casciola, M. (2003). Composite Membranes For Medium-Temperature Pem Fuel Cells. Annual Review of Materials Research , 33, 129-154. Since the key obstacles to increased commercialization of PEM fuel-cells is due to their low-proton conductivity, especially the minimal relative humidity of their ionomeric membranes, Alberti and Casciola in this article explain one possible way out of the predicament based on development of composite membranes. Alberti and Casciola (2003), asserts that composite membranes with suitable fillers which are dispersed within the ionomer matrix can aid in countering elevated methanol permeability, in addition to reducing mechanical changes at temperatures exceeding 130°C within the cells (Alberti & Casciola, 2003). The article begins with an explanation of the preparation methods used to generate composite membranes, with a focus on compound ionomeric membranes which contain not just silica, but heteropolyacids and encrusted metal phosphate, as well as phosphonates. There is also an explanation of new approaches used in the groundwork of nano-composite membranes, particularly filling of permeable polymeric membranes which have extremely conductive zirconium-phosphonates. Given that low-temperature proton swap membranes have disadvantages which can decrease their efficiency, the article provides details on the expected manipulation of size plus orientation of silica and heteropolyacids on the membrane characteristics, and which can counter the problems arising from proton exchange. For instance, they mention manipulation of orientation to conform with conductivity and absorbency to methanol. Alberti & Casciola (2003) conclude that sulfonated hydrocarbon-polymers, together with blend polymers can generate remarkable enhancement in mechanical nature of the fuel cells, especially proton conductivity within high temperatures. However, they do not provide extensive explanation or tests of how inputting of metallic oxides, like MO2 inside the polymer matrix, can enhance water maintenance nature of membrane. This is because awareness of the chemistry of exodus of protonic imperfections throughout the membrane is important in determining the size and orientation of the silica. Nevertheless the study is useful in understanding how to capture, amass and use high-grade dissipate heat, including Fuel chemical alteration when utilizing oxide materials. Asensio, J. A., Sánchez, E. M., & Gómez-Romero, P. (2010). Proton-conducting membranes based on benzimidazole polymers for high-temperature PEM fuel cells. A chemical quest. Chem Soc Rev , 39 (8), 3210-3239. For massive commercialization of high temperature PEM fuel-cells to be possible, studies have to concentrate more on ceramic membranes which will enhance sulphur tolerance along with long-term stability. Therefore, this study by Asensio, Sanchez & Gomez-Romero seeks to explain the progress of high-temperature PEM fuel-cells having ceramic membranes. Since the cells operate at temperatures ranging from 150oC-200o C problems do arise such as CO intolerance, poorer kinetics, and poor water retention among many others (Asensio, Sánchez, & Gómez-Romero, 2010). The study evaluates solutions done on Polybenzimidazole membranes, and which have been nano-impregnated using phosphoric acid, so as to act as electrolytes in high temperatures PEM fuel cells. Hence, commercially produced polybenzimidazole is used in membranes is filled with every form of strong inorganic acids. The study further analyzes ABPBI polymer and other polybenzimidazole form membranes, since strong inorganic acids and alkaline electrolytes are used to saturate benzimidazole membranes. An assessment of hybrid substances derived from polybenzimidazoles, inorganic proton conductors like heteropoly acids, and sulfonated derivatives derived from polymers, seems to show good performance within elevated temperature PEM fuel cells. Asensio, Sánchez, & Gómez-Romero, attributes this to their positive proton conductivity, including mechanical stability (2010). Hence, they conclude that an assessment of these polymers can certainly contribute to the development of fresh design methods, ranging from adjustment of straight channel outline, to advancement of channels through designs based on fractal models (Asensio, Sánchez, & Gómez-Romero, 2010). Since the main challenge is to come up with PEM cell-fuels that are based on not just high conductivity, but also higher, mechanical, chemical and thermal stability, then the article compared to the one by Alberti & Casciola (2003) has elaborated clearly on the molecular design, including the synthesis of all-polymeric electrolytes and which will depend completely on protons structure-diffusion. Zaidi, J. (2009). Research Trends in Polymer Electrolyte Membrane for PEMFC. Polymer Membranes for Fuel Cells. Springer Science. Zaidi reviews the various scientific progressions of polymeric membranes, and as such, the discussion centers on three approaches used by researchers globally in the development and formation of substitute membranes (2009). This comprises transforming perfluorinated-ionomer membranes, utilization of aromatic-hydrocarbon-polymers membranes, in addition to complex membranes founded on concrete inorganic but proton conducting components. Another approach includes using organic polymer-matrix and acid-base blends with their composite, so as to enhance their water maintenance properties. Zaidi notes that the desired characteristics of a membrane utilized as proton conductor, should include not just chemical stability but also thermal, hydrolytic and electrochemical stability. This will then enhance high proton conductivity and enhanced water uptake within elevated temperatures, so as to support elevated currents under least resistive losses or zero electric-conductivities (Zaidi, 2009). Hence, Zaidi argues that more focus should be on trying to modify the fundamental concepts of Nafion membranes using diverse processes like plasma etching or palladium sputtering (2009). One unique aspect of this article is that it provides details on how sulfonated polyether-ether ketone, which is one of nafion polymer, can be used to create composite membranes. This is more so regarding creation of temperature steady membranes which survive temperatures ranging from 100 to 150 ° C (Zaidi, 2009). Such membranes are created from composite membrane designs, in order to minimize methanol crossover, as well as in enhancing conductivity and water administration during high temperature. Nevertheless, it would have been better if Zaidi could explain further how doped PBI which acts as proton conductivity similar to Nafio, may be preserved while practically removing intersection of methanol. This is because by making PBi to be an inherent proton-conductor it would create a complex polymer electrolyte which will be a good proton conductor that may minimize crossover by methanol. Bose, S., & et tal. (2011). Polymer membranes for high temperature proton exchange membrane fuel cell: Recent advances and challenges. Progress in Polymer Science, 36, 813–843. Given that elevated temperature PEMFC provides several rewards like high proton-conductivity, minimal fuel permeability, and reduced electro-osmotic drag-coefficient, they are now used extensively as they do not possess limitations like carbon monoxide poisoning, poor heat management, or water leaching. Thus, the aim of this research paper is to evaluate the advantages of HT-PEMFC advancement and the technological restraints. The researchers have analyzed several categories of polymers like sulfonated hydrocarbon polymers, acid–pedestal polymers and merged polymers, in order to understand the consequence of inorganic-additives on the functionality of high temperature PEM fuel cells (Bose & et tal, 2011). The conclusion is that high temperatures PEM bring about unique features in fuel cells such as chemical plus thermal stability, and enhanced mechanical properties. Furthermore, the researchers argue that the proton conductivity, along with cell output of polymeric membranes can be enhanced through elevated temperature treatment, and this will also improve the mechanical plus water maintenance properties (Bose & et tal, 2011). However they propose that a further assessment should be done regarding fusion of polymers on membrane fabrications, in addition to physicochemical characterization. Bose & et tal, (2011) observes that this will help to attain further enhancements in certain sections like optimization of thermal plus chemical stability, acid administration, and enhancement of fundamental interface linking electrode to membrane. This is more so since high temperature functionality often results in dehydration, and which can in the end depreciate membrane performance. The most definitive issue about this article is that the researchers provide solutions to retaining water at elevated temperatures such as integration of inorganic additives with hydrophobic-polymer membranes, or application of non aqueous but minimal volatility solvents instead of water thus acting as enhanced proton-acceptor (Bose & et tal, 2011). However, they have not provided further explanation on how enhancement of mechanical properties or proton conductivity within high temperatures can be attained when using solid condition protonic conductors instead of water. This is because such information will help to guide how nano-shaped metal electro-catalysts can replace platinum in fuel cells. Loyselle, P., & Prokopius, K. (2011). Teledyne Energy Systems, Inc., Proton Exchange Member (PEM) Fuel Cell Engineering Model Powerplant. Cleveland, Ohio: NASA. This report provides the findings of tests meant to mark the concluding phase of PEM fuel-cell technology in replacing alkaline fuel-cells technology used on the next generation future space vehicles (Loyselle & Prokopius, 2011). The report details preliminary performance assessment test results of PEM in terms of its stability, performance, existence, gravity autonomy and reaction time. The major observation during the test occurred during the initial half of polarization-curve, as the stack voltage of alkaline fuel cells was lesser than that of Teledyne PEM fuel cells (Loyselle & Prokopius, 2011). Nevertheless, second half observations revealed the voltages were almost identical and they attribute the low first half voltage in PEM fuel cells to minor drying. The study also asserted that the PEM Fuel cell performance relies so much on reactant pressures, since higher pressures considerably enhances the cell general performance. Hence, the elevated hydrogen pressure enhanced the fuel-cell functionality resulting in slightly superior stack voltage (Loyselle & Prokopius, 2011). Furthermore, moments after start-up, PEM fuel cells voltages became closely spaced and even managing to sustain spacing all through the test. Hence indicating that even in swift start-up states, pressure and temperature are consistent all through the cell stack. Even though the report tests data can be used to quantify any shifts in performance of the PEMFC stacks when functioning under diverse physical settings, this study unlike the other studies fails to mention how any decrease in platinum-loading across the catalyst layers can be acquired, while simultaneously maintaining elevated performance of the PEMFC can be attained. Furthermore, it has failed to account quantitatively how the membrane humidification could impact the lifespan of the stack, especially the number of startup or stop cycle or even the number of startup from unmoving or frozen state. Moghaddam, S., & ettal. (2010). An inorganic–organic proton exchange membrane for fuel cells with a controlled nanoscale pore structure. Nature Nanotechnology, 5, 230 - 236. The focus of this study centers on how PEMFC commercial development is being impeded by setbacks in membrane electrode creation. Hence, the aim of the study is to exhibit how silicon-pedestal inorganic and organic membrane can provide numerous benefits compared to Nafion, which is the most commonly used membrane in PEM hydrogen fuel-cells (Moghaddam & et tal, 2010). The findings reveal that the key to attaining such benefits lies in the fabrication of silicon membrane, using pores that have diameters ranging from ~5 to 7 nm, and then combining with a self-amassed molecular mono-layer resting on the aperture surface (Moghaddam & ettal, 2010). Furthermore, the study observes that it is crucial to seal the pores using a coating of permeable silica, since the silica layer minimizes the width of the pores. This then guarantees hydration, and according to Moghaddam & et tal, it can result in proton conductivity which has been calculated to be between 2-3 orders of scale higher, compared to Nafion especially during low humidity (2010). Moghaddam & ettal (2010), concludes that silicon-pedestal inorganic and organic membranes are better than Nafio since they not only have superior proton conductivity, but they also do not undergo volumetric size shift like Nafion. In addition, their membrane electrodes have high production and assembly capacity compared to Nafion. Moreover, the membrane electrode collection developed with silica exchange membrane, generates an array of magnitude superior power density, compared to those attained using dry hydrogen coupled with an air-gasping cathode. However, despite of all these benefits, Moghaddam & et tal, asserts that additional work need to be conducted on the silica membrane, so as to develop materials having adequate long-standing stabilities, as well as mechanical strengths (2010). This study compared to the rest has managed to evaluate critically every advantage of silica-based membrane materials with a focus on synthesis techniques and characterizations. Nguyen, L., Mighri, F., Deyrail, Y., & Elkoun, S. (2010). Conductive Materials for Proton Exchange Membrane Fuel Cell Bipolar Plates Made from PVDF, PET and Co-continuous PVDF/PET Filled with Carbon Additives. Fuel Cells, 10, 938–948. Given that non-fluorinated polymer-membrane is now increasingly being used instead of per-fluorosulfonic acid-membrane, this research work seeks to develop and illustrate electrically conductive components. Hence, the focus is on proton swap-over PEM fuel-cells and bipolar plates. The findings reveal that lower resistivity can be generated with polyvinylidene fluoride when combined with conductive carbon-black powder. This is because they have elevated interfacial energy, higher density and high crystalline nature (Nguyen, Mighri, Deyrail, & Elkoun, 2010). Furthermore, the reduced cooling rates assist in maintaining minimal values of end to end plane resistivity. The key requirements identified for polyvinylidene fluoride to be used as a polymer fuel-cell is ample membrane mechanical potency at every level of operation or sulfonation. Nguyen, Mighri, Deyrail, & Elkoun, also asserts that it should have strong hydration capacity in order to permit elevated proton conductivity, in addition to being stable in an aggressive setting of fuel cells. This should be more so on in terms of attaining thermohydrolytic and chemical stability (Nguyen, Mighri, Deyrail, & Elkoun, 2010). The most notable thing about the bipolar plates used in the study, is that they were prepared in a matrix phase, from extremely conductive combination of polyethylene terephthalate together with polyvinylidene fluoride. This then generates minimal resistivity values within controlled compositions that guarantee polyethylene terephthalate, together with polyvinylidene fluoride co-continuous morphology. Furthermore, the slow cooling levels seemed to attain lowest levels of end to end plane resistivity, due to elevated crystallinity acquired under reduced cooling rates. This then results in smaller amorphous phases whereby carbon particles become increasingly concentrated. Vishnyakov, V. M. (2006). Proton exchange membrane fuel cells. Vacuum. Journal of Vacuum Science & Technology , 80, 1053–1065. This research paper provides an overview of the progression and present technical issues related to proton exchange membrane fuel cells. The key objective of the researcher, Vishnyakov is to provide a brief overview of the fundamental science regarding PEMFC and to illustrate a feasible strategy of implementing the cells, including the feasibility of applying them in vacuum-based system during PEMFC manufacturing. Vishnyakov notes that the requirements of PEM fuel cells do not entirely place emphasis on performance or price but focus considerably on accessibility of the fuels, environmental plus human-health effects, as well as their circulation and storage mechanisms (2006). The problem identified is balancing all of these factors with the various futuristic unknowns. Vishnyakov asserts that the solution for bringing down prices is to initiate mass production of assembly parts while concurrently making new polymers to be cheaper than Nafion (2006). Vishnyakov observes that vacuum-based components production, including corresponding treatment methods can be applied for every PEM fuel-cell element, in addition to devise monitoring. Thus, the use of vacuum-based production and treatment methods will not just increase performance of fuel-cells, but also help produce materials which are not easy or even impossible to create through what he refers to as ‘‘wet technology’’ (Vishnyakov, 2006). The conclusion arrived at is that the use of vacuum deposited objects will help in minimizing environmental brunt of fuel-cell manufacturing, since they create a minimal amount of pollutants compared to conventional solvent-based methods. In addition, plasma treatments can enhance the catalyst surfaces and backplates, including the diffusion coating and surfaces used in fuel-cell assembly (Vishnyakov, 2006). The shortcoming of this article is that it does not address how fuel-cells lifespan will be affected by vacuum-based techniques, especially membrane humidification, figure of stop and start cycle, the quantity of power-cycle or amplitude span, as well as amount of starts from frozen condition. Summary of Papers This paper has evaluated the various research studies recent advances and challenges regarding the commercial development of PEMFC. Most of the articles have compared the advantages derived from high temperature PEMFC compared to low temperature PEMFC, such as high proton conductivity and low permeability. Even though Proton Exchange Membrane Fuel Cells have large potential, there has been minimal development of appropriate technology and materials. Hence, the papers have indicated the major approaches to make PEMFC work more effectively and environmentally friendly. Based on the assessments, this paper argues that the major weakness of PEMFC centers on how to limit the heat and poor water retention. The solutions presented includes incorporation of inorganic and organic additives to hydrophobic polymer membranes, to silica, to the use of non aqueous but low volatile solvents in replacing water as the proton acceptor within the polymer membrane. However, hydrophobic polymer membranes seems to be the most effective means of attaining a solid state protonic conductor in dealing with water retention. The articles have also provided details on how to increase PEMFC power, reduce environmental effects while at the same time reduce cost. Hence, vacuum-based material production and treatment techniques can be used for generation, purification and storage of hydrogen. By using this technique, cost and pollution from fuel cell would be reduced considerably. Furthermore, research trends in polymer electrolyte membranes have brought out the three different approaches that are somewhat effective. They include modifying perfluorinated ionomer membranes and the aromatic hydrocarbon membranes so as to aid conductivity. The other is to create polymer electrolyte that have been combined with membranes derived from solid inorganic proton. Therefore, since such approaches are currently applicable, the conventional Nafion membranes will be replaced. Read More