Papers by Keyword: Proton Exchange Membrane Fuel Cell

Abstract: Proton Exchange Membrane Fuel Cell is a promising green energy conversion machine. However, some drawbacks, such as Pt corrosion on the cathode side, the high price of Pt, Nafion membrane, and the need for the high precision assembly process, limit their commercialization. In this study, PtCrCo alloy which is supported by nitrogen-doped activated carbon was synthesized by facile method to increase electrochemical performance as a cathode catalyst and reduce Pt catalyst usage. Nitrogen-doped Activated Carbon/PtCrCo/Nitrogen-doped Carbon (NAC/PtCrCo/N) catalyst was investigated to analyze the effect of increasing the composition of nitrogen-doped activated carbon in the synthesis process on the morphology and electrochemical performances of the catalyst. Polyaniline (PANI) as Nitrogen precursor was added to Activated Carbon (AC) powder with ratio of AC to PANI; 1:0, 3:1, 1:1, 1:3, as called AC, NAC1, NAC2, and NAC3 respectively. The catalyst synthesis process is carried out with the four activated carbon supports. Material characterizations were carried out using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller (BET), Cyclic Voltametry (CV), and Linear Sweep Voltametry (LSV). The XRD measurement shows that the addition of nitrogen doping tends to reduce the diffraction peak intensity of nitrogen-doped activated carbon compared to the pristine carbon. The doping also increases the surface area of the activated carbon as measured by the BET method. Nitrogen doping increases the conductivity and the addition of alloys can add better stability and catalytic activity for cyclic voltammetry results of the four catalysts cannot be calculated. The NAC3/Pt-Cr-Co/N electrocatalyst exhibited the highest initial potential at ~1 mAcm^-2 of 0.997 V compared to the other four samples. On the other hand, AC/Pt-Cr-Co/N catalyst has the highest current density value of 22.156 mAcm^-2.

Abstract: Titanium is promising candidates for bipolar plates in fuel cell, electrolysis, etc., due to the excellent corrosion resistance of titanium oxide (TiO₂). However, TiO₂ also possesses poor electrical conductivity and leads to high power losses, so that the conductivity of titanium needs to be further improved. In this work, the effect of thirty-nine metals on the conductivity of TiO₂ was studied based on the first-principles merged with the Boltzmann transport equation and Deformation potential theory. The results show that the conductivity meets the target of 100 S∙cm^-1 proposed by the U.S. Department of Energy when TiO₂ doped with Cr, Sb, Ga, etc. The Sb-doped not only enhances carrier concentration, reduces relaxation time, but also improve the chemical bond. The intermediate bands induced by Au, W, Rh, etc. is a special conductivity enhanced mechanism.

Abstract: Polybenzimidazole (PBI) nanofiber membranes were prepared using electrospinning potential of 15 kV and 0.2 ml/h flow rate at different PBI concentrations (6.5 and 7.5 w/v%) with the solvent mixture ratio (DMAc:DMF) of 1:1 and 2:1, respectively. This study investigated the properties of the polymeric solution and the effects of solvent ratio and concentration on morphology, hydrophobicity and mechanical properties of PBI nanofiber membranes. The solvent mixture ratio and spinning solution properties are not significantly different than the effect of polymer concentration on the viscosity. The viscosity and surface tension of spinning solutions increases with an increase in the concentration of PBI. It was observed that the average diameter of nanofibers was 75 and 97 nm for 6.5 and 7.5 w/v% PBI spinning solution, respectively. Moreover, the contact angle values range from 111 to 125°. This observation reflects that the nanofiber membranes are hydrophobic. Another finding is that the nanofiber membranes with 7.5 w/v% of PBI showed excellent mechanical properties with the maximum stress value of 4.20 ± 0.29 MPa. The finding also shows that the polymer concentration on the spinning solution influences the structure and morphology of the nanofibers. On the other hand, the solvent mixture ratio does not have any significant impact on the nanofiber membranes properties.

Abstract: Various hydrophilic metal oxides are added to the catalyst layers of anodes because they absorb the water that diffuses from cell cathodes. In this study, the transfer method was employed to form an anode catalyst coated membrane by using hydrophilic TiO₂ nanopowder to improve the performance levels of the proton exchange membrane in low-or zero-humidification conditions. The various TiO₂ loadings added to anode thin film catalyst layers were compared to determine how the TiO₂ loadings affected the fuel cell performance levels at various cell temperatures and gas humidification conditions. The results indicated that adding 0.035mg/cm² of TiO₂ is optimal when the fuel cell temperature is 50 °C or 70 °C.

Abstract: Using the dry method-prepared polyacrylonitrile based carbon fibers as raw the material, carbon paper applied for proton exchange membrane fuel cells was prepared by the processes of molding, high temperature carbonization, chemical vapor deposition (CVD), and graphitization. The effects of resin carbon content and subsequent heat-treatment process parameters on the properties of carbon paper were studied. The results show that: the resin carbon content is an important factor to affect the density, thickness, through-plane resistivity and porosity of carbon paper. When the resin carbon content is 20%, the thickness of carbon paper is 0.20mm, the density is 0.41g/cm³, and the porosity is 74.5%, in line with requirements of the fuel cell. When the heating time is 4 hours, the porosity is 71.9%.

Abstract: Water management inside a proton exchange membrane fuel cell is critical both for stable operation and desired performance. This paper presents the relations that govern water transport mechanisms, describes and proposes a control strategy for membrane conductivity manipulation using an observer and two controllers. The Simulink model is showing successful control of membrane conductivity when density current changes while water vapor pressures are maintained within the safe limits. Using the proposed control strategy, further work can be conducted in the area of feed forward and advanced control of water management in PEM fuel cells.

Abstract: A new series of hydrophobic-hydrophilic multiblock sulfonated poly (arylene ether ketone)-b-poly (arylene ether ketone) copolymers were successfully synthesized and evaluated for use as proton exchange membranes (PEMs). The membrane properties of block copolymers including ion exchange capacities (IECs), water uptake and proton conductivities were characterized for the multiblock copolymers and compared with random sulfonated poly (arylene ether) s and other multiblock copolymer membranes at similar ion exchange capacity value. This series of multiblock copolymers showed moderate conductivities up to 0.063 S/cm at 80 °C with very low water uptake of 19%. Therefore, they are considered to be promising PEM materials for fuel cells.

Abstract: A new series of hydrophobic-hydrophilic multiblock copolymers derived from fluorine terminated poly (arylene ether ketone) as hydrophobic blocks and phenoxide terminated sulfonated poly (arylene ether sulfone) as hydrophilic blocks were successfully synthesized and evaluated for use as proton exchange membranes (PEMs). All the hydrophobic and hydrophilic oligomers were synthesized via molecular-weight controlled step growth polymerization of the monomers. ¹H NMR spectra were used as characterization tool to determine the telechelic oligomers molecular weight and multiblock copolymers structure. The morphologies of multiblock copolymers were investigated by transmission electron microscopy (TEM), which showed they had a clear microphase-separated structure between the hydrophilic domains and hydrophobic domains. All the sulfonated poly (arylene ether sulfone)-b-poly (arylene ether ketone) copolymers can easily be cast into tough membranes for applications in proton exchange membrane.

Abstract: Combustion engines are increasingly being regarded as unsustainable in the long-term, because of their negative impact on the environment (e.g. pollution, green-house gas production, and global warming). This has generated worldwide interest in propulsion systems based on renewable alternative energy sources for the future. Fuel cell technology is a promising alternative power source because of their high specific energy, efficiency, and reliability. Hydrogen proton exchange membrane fuel cell (PEMFC) in particular produces zero carbon emissions by having only water vapor as the exhaust. Although there has been much research by automotive industries in developing fuel cell hybrid electric vehicles (FCHEV), fuel cell research for aircraft application is relatively new. Therefore, there is a pressing need for research related to development of aircraft fuel cell electric propulsion systems. Universiti Teknologi MARA (UiTM) is conducting static experiments on different configurations of fuel cell electric propulsion systems. The objective of this study is to understand the behavior of a PEMFC propulsion system under a ground-based static test. A 1 kW PEMFC was used as the main power source for a brushless DC motor electric propulsion system. The electrical characteristics, rotational speed, and thrust data were presented for two different electrical propellers. Analyses of the results were used to characterize the effectiveness of the fuel cell system and its balance of plant. The results were beneficial as a predictive method on defining the optimum electric propulsion system performance needed for future actual flight development.

Abstract: This study developed a heating mechanism applicable to hydrogen storage tank, in order to enhance the stability and durability of proton exchange membrane fuel cell (PEMFC). This study discussed two heating modes. The first mode was using heating wire to wind the hydrogen storage tank body. Heating wires were used to wind the upper, middle and lower parts of the hydrogen storage tank and the whole tank respectively for discussion. The second heating mode was to use the PEMFC cathode waste heat to heat the hydrogen storage tank body. This study discussed the variations of hydrogen release rate and tank body temperature with the hydrogen release time in different heating mechanisms. The research results can serve as reference for system design in various applications.