Papers by Keyword: PEMFC

Abstract: In the fabrication of fuel cell electrodes, applying catalyst ink onto a substrate is crucial. The performance of the proton exchange membrane fuel cell (PEMFC) is subsequently impacted by how the catalyst is applied onto substrate as well as in terms of its resulting morphology. In this study, a direct catalyst ink spraying approach was done in order to investigate transfer efficiency and surface morphology for different concentrations of ink. The concentration of catalyst ink used in the spraying process are 0.5, 1.0, 1.5, 2.0 and 2.5 mg/ml with fixed loading of 1.0 mg/cm². The transfer efficiency of the catalyst inks was calculated neglecting human error during spraying. The coating thickness and distribution of the resulting catalysts were analysed via Field Emission – Scanning Electron Microscope (FESEM).

Abstract: With the development of PEMFC, the process of commercial fuel cell is also accelerating. As one of the key points of fuel cell, catalyst is facing the problem of how to improve its performance and life. In order to improve the durability of fuel cell catalyst, this paper will study the preparation of Pt nanowire catalyst, so as to improve the electrochemical performance and durability of the catalyst. PtNWs were prepared by soft template method. By TEM, we can clearly see that PtNWs with uniform length were obtained by soft template method. Because of the special structure, the ORR performance of the catalyst was better. The test results showed that the hydrogen peroxide desorption from PtNWs was easier, and the half wave potential of LSV curve shifted forward, which indicated that the NWs catalyst performed better ORR performance. The linear structure of PtNWs is not easy to dissolve and lose compared with Pt particles, and the linear structure is more conducive to the transfer of materials and electrons at the reaction interface, so it can show better performance and life.

Abstract: A highly active Platinum Group Metal (PGM) and non-PGM electrocatalysts with thermally extruded nanotubes have been prepared for Proton Exchange Membrane (PEM) fuel cell by sintering Nickel zeolitic imidazole framework (Ni-ZIF). Preeminent electro-catalytic activities have been observed through single fuel cell tests and rotating disk electrode (RDE). This study involves the comparison of Oxygen Reduction Reaction (ORR) activities and fuel cell (FC) test station performance of two catalyst Nickel and Platinum mixed Nickel nanotubes (Ni NT, Ni/Pt NT) respectively. The acidic cells with corresponding Ni and Ni/Pt catalysts delivers peak power densities of 325 mWcm^-2 and 455 mWcm^-2 at 75 °C inside fuel cell. Our results indicate that, the synthesized Nickel nanotubes has profound effect on catalytic performance of both PGM and non-PGM electro catalysts.

Abstract: This paper investigates the physical properties and electrochemical properties of the innovative non-precious metal catalyst using different carbon types. The cathode catalyst for PEMFC (Proton Exchange Membrane Fuel Cell) is an important part of fuel cell because the reaction of the cathode is three times lower than the anode. Otherwise, the high cost of Pt/C catalyst for cathode needs to be replaced using low-cost material. Therefore, this research fabricated Pt free catalyst. FeCl₃.6H₂O was used as a metal precursor. Urea and PVP as a nitrogen (N) source were mixed with carbon. The variations of carbon are Graphite (Gt), Charcoal Active (CA), and Calcined Petroleum Coke (CPC). As prepared catalysts, were noted as Fe/N-Gt, Fe/N-CA, and Fe/N-CPC. Catalysts without nitrogen addition also were synthesized such as Fe-Gt, Fe-CA, and Fe-CPC for comparison. The electrochemical properties can be evaluated form Cycle Voltammograms (CV) curve. Graphite supported catalyst has anodic and cathodic peak otherwise has the lowest capacity. It means that the redox reaction occurs during CV measurement for Fe/N-Gt and Fe-Gt catalyst. Nitrogen addition of graphite supported catalyst has a higher current density than Fe-Gt catalyst. The morphology of the catalyst was identified by Scanning Electron Microscope (SEM). Different particle shape for carbon types can be observed by SEM image of obtained catalyst. Energy Dispersive X-Ray EDX to identify the chemical composition. Nitrogen-doped carbon caused the formation of Fe₂O₃ and it was determined by X-ray diffraction (XRD).

Abstract: There is a significant effect for the performance of proton exchange membrane fuel cell with the liquid water generated in cathode channel during the operation process In this paper, based on the numerical simulation of three-dimensional and VOF model of multiphase flow, according to the different flow channel design and the change of different inlet temperature, the transport phenomena of multiphase flow in PEMFC is discussed at temperature effect. In U-shaped cathode channel with bump scale (h/H=1/4), a long water film is assumed to cover the surface of the gas diffusion layer at the entrance. Under the simulated oxygen flow conditions of inlet 200 Reynolds number, 4.4 Weber number and inlet temperature 333K, the water film heated is not obviously affected by oxygen flow from inlet channel to bend channel. Subsequently, the shape of water film is elongated and broken from outflow of bend channel to outlet channel. The computational results are obtained that the residual broken water film can be existed in the outlet channel. The flow field temperature can affect the residual flow rate of water film in the channel. The residual rate of water film in the hot flow field is lower than that in the cold flow field.

Abstract: Nitrogen –doped carbon material using non-precious metal was developed as catalyst fuel cell (PEMFC). In the PEMFC, the cathode reaction occurs three times slower than anode reaction. Oxygen reduction reaction (ORR) in the cathode has major limit performance. Pt/C was used as high-cost catalyst materials but many researchers concerned to improve cathode catalyst performance using high-performance and low-cost materials. Nitrogen based active sites on carbon has important role for oxygen reduction reactions process. In this study, compositions of carbon for Fe-N-C were investigated to understand the electrochemical properties and morphological analysis. Urea and PVP as nitrogen (N) source was mixed with graphite (Gt). The ratio of Gt and N were 1:1, 3:1, and 1:3. The mixture was added to FeCl₃.6H₂O dissolved in ethanol to produce Fe-N/C catalyst. Subsequently powder was introduced to the furnace for the pyrolysis. The catalyst products were analyzed using Potentiostat to show the electrochemical properties of catalyst, X-Ray Diffractometer (XRD) was used to know the compound or phases after catalyst syntheses, Scanning Electron Microscope – Energy Dispersive X-Ray (SEM-EDX) was used to identify the morphology and the chemical compositions of catalyst. As a result, Fe – Gt : N = 1:3 catalyst had the greatest electrochemical properties which is identified by large area of CV curve. This catalyst also had the highest current density for reduction reaction. The presence of Fe₂O₃ and FeS caused the degreasing of catalytic activity. As conclusions of this research, carbon composition had the important rule to improve the ORR activity.

Abstract: An irreversible model of proton exchange membrane fuel cells working at steady-state is established, in which the irreversibility resulting from overpotentials, internal currents and leakage currents are taken into account. In this paper, the irreversibility of fuel cell is expounded mainly from electrochemistry. The general performance characteristic curves are generated including output voltage, output power and output efficiency. In addition, the irreversibility of a class of PEMFC is studied by changing the operating conditions (controllable factors) of the fuel cell, including effect of operating temperature, operating pressure and leakage current. The results provide a theoretical basis for both the operation and optimal design of real PEM fuel cells.

Abstract: Highly porous ZIF-67 (Zeolitic imidazole framework) has a conductive crystalline metal organic framework (MOF) structure which was served as a precursor and template for the preparation of nitrogen-doped carbon nanotubes (NCNTs) electrocatalysts. As a first step, the chloroplatinic acid, a platinum (Pt) precursor was infiltrated in ZIF-67 with a precise amount to obtain 0.12 mg.cm^-2 Pt loading. Later, the infiltrated structure was calcined at 700°C in Ar:H₂ (90:10 vol%) gas mixture. Multi-walled nitrogen-doped carbon nanotubes were grown on the surface of ZIF-67 crystals following thermal activation at 700°C. The resulting PtCo-NCNTs electrocatalysts were deposited on Nafion-212 solid electrolyte membrane by spray technique to study the oxygen reduction reaction (ORR) in the presence of H₂/O₂ gases in a temperature range of 50-70°C. The present study elucidates the performance of nitrogen-doped carbon nanotubes ORR electrocatalysts derived from ZIF-67 and the effects of membrane electrode assembly (MEA) steaming on the performance of proton exchange membrane fuel cell (PEMFC) employing PtCo-NCNTs as ORR electrocatalysts. We observed that the peak power density at 70°C was 450 mW/cm² for steamed membrane electrode assembly (MEA) compared to 392 mW/cm² for an identical MEA without steaming.

Abstract: Bipolar plates (BPPs) serve multiple roles in polymer electrolyte membrane fuel cells (PEMFCs). When assembled in a stack, they provide the structural backbone of the stack, plus serial electronic connections. They also provide gas (air and fuel) and coolant distribution pathways. Traditionally, bipolar plates have been made of carbon, but these are being replaced in favor of metal bipolar plates made of stamped foils. The Naval Research Laboratory has explored making titanium metal BPPs using 3D printing methods (direct metal laser sintering – DMLS) and superplastic forming, and then using a gold/TiO₂ surface layer for corrosion resistance. The 3D printed plates are made as one piece with the coolant flow internal to the resulting 2-mm thick structure. Their surface roughness requires smoothing prior to coating to increase their cell-to-cell conductivity. We found that 3D printed cells with 22 and 66 cm² active areas are slightly warped, preventing the robust sealing of the stacks. The formed plates are made in separate pieces and then joined. Despite the high temperatures required for superplastic forming, the resulting plates are thin and lightweight, making them highly attractive for lightweight compact PEMFC stacks.

Abstract: Proton Exchange Membrane Fuel Cell (PEMFC) is a device that generates electricity through an electrochemical reaction of oxygen air and hydrogen fuel. Thetransportofoxidantand fuel through the bipolarplatesis a significant factor affecting the cell performance. Currently, present work concentrates highly on flow field layout and channels design configurations. In this paper, the development two flow field layouts are discussed with different inlet/outlet channel ratio. Serpentine-paralleldesignisusedasthe base layout. The flow fields have inlet/outlet channel ratio of 1:1 and multiple inlet 2:1 configurations. Graphite is used as theplate material.Theanodeflowchannelis 2 mmx 1.2 mmx 2 mm meanwhile the cathode channel is 2 mm x 0.5 mm x 2 mm fora xbxwrespectively.Theactiveareais 25 cm² with 5 cmx 5 cm dimensions. The fields were fabricated by Roland EGX-360 Desktop Engraver machine that involved drilling and profiling process. The fuel cell assembly process is explained in detail. The gasketmaterialis made from two materials which are Polyimide and Silicon. A series of pre-conditioning experiments were carried out in both fuel cells for confident purposes.