Fuel Cells最新文献

To alleviate water flooding in cathode electrodes of polymer electrolyte fuel cells (PEFCs), it is necessary to understand the water transport inside diffusion media and design the electrode/channel structure for facilitating the water discharge from porous electrodes to gas channels. The authors proposed the novel modified structure combining the electrode perforation with the channel hydrophilization in their previous study and revealed that its structure has the possibility of encouraging the through-plane water removal from the diffusion media and the oxygen diffusivity to the reaction sites. This study investigated the effects of perforation size and cell compression on the water transport in the cathode diffusion media of the structure-modified cell using x-ray radiography. The constant current operation tests were also conducted to characterize the cell performance. It was shown that the 300 µm perforation and low compression have a large effect on encouraging the in-plane water drainage from the diffusion media to the groove or hole, resulting in reducing the voltage loss due to the water flooding. This innovative structural modification can be put to practical use because of its simple manufacturing process and low cost.

It is widely recognized that direct internal reforming (DIR) solid oxide fuel cells (SOFCs) fueled by biomass are one of the eco-friendly and high-power generation methods. In existing cell configurations, however, the performance and durability degradation of SOFCs are induced by a strong endothermic dry reforming of methane (DRM). They are required to understand the fundamental thermal distribution mechanism and construct new cell configurations to relax thermal distribution effects. We performed a three-dimensional thermal distribution analysis coupled with computational fluid dynamics and chemical reactions in DIR-SOFCs with the three-cell stacking reactor model as a more practical model. As a result of the simulation for temperature distribution in each case of homogeneous and functionally graded paper structure catalysts (PSCs), we have found that the largest temperature drop occurs near the inlet in the bottom layer compared with the upper and middle layers in both cases and temperature distribution is milder in the functionally graded PSC. We also have found the importance of two-dimensional reaction rate controls in gas flow and cell staking directions to uniform temperature distribution of each layer. Furthermore, we investigated the effects of exothermic electrochemical reaction in the anode on thermal distribution.

The performance degradation of proton exchange membrane fuel cells (PEMFC) in low-temperature extreme environments is one of the challenges on the way to their commercialization, and it is important to investigate the performance changes of fuel cells in low-temperature environments for their future development. In this paper, the cold-start performance of fuel cells with different initial water content of the membrane and starting modes was compared. Lowering the initial water content of the membrane could enhance the water storage capacity of the cell and improve the cold-starting performance of the cell, but infinitely low initial water content might cause the reverse polarity phenomenon, which would cause serious corrosion and degradation of the membrane electrode assembly (MEA). In constant voltage starting mode, reducing the starting voltage could increase the heat production of the cell, but it would weaken the water storage capacity of the cell. In the constant current starting process, lowering the starting current could improve the water storage capacity of the cell, which was beneficial to the cold start of the cell. It was also found that the MEA with cold start failure had a serious performance degradation, and cold start failure needed to be avoided as much as possible.

This study presents an integrated heat recovery-proton exchange membrane (IHR-PEM) fuel cell system designed for lightweight vehicles powered by a 2 kW PEM fuel cell. The IHR system captures waste heat through multiple heat exchangers and integrates thermoelectric generator (TEG) modules for electrical regeneration and hydrogen preheating, enhancing PEM fuel cell performance. Utilizing the temperature gradient between the fuel cell's exhaust and the ambient environment, the system effectively converts waste heat into electrical energy, improving energy efficiency. Experimental evaluation under various operating parameters, including cruising speeds, PEM fuel cell loads, rejuvenation conditions, and electrical regeneration strategies, demonstrated the system's effectiveness. Results revealed waste heat absorption of up to 8.5 W and hydrogen preheating by 19°C, leading to an 11.5% increase in electrical power production and a maximum PEM fuel cell efficiency improvement of 11%. This study advances waste heat recovery (WHR) technologies in fuel cell-based transportation, significantly improving energy efficiency and reducing carbon emissions. The findings provide valuable insights into the integration of regenerative WHR systems for lightweight vehicles, fostering the development of sustainable and energy-efficient transportation solutions.

As the flow field structure has a crucial influence on the performance of the proton exchange membrane fuel cell, in this research, the radial flow field R-0 is designed and optimized based on the characteristics of the annular serpentine and annular flow channels to form combined flow field structure (R-1 to R-5). Subsequently, a three-dimensional and two-phase model is established and the effects of each flow field on the cell performance are numerically investigated. Results indicate that the R-0 can enhance the gas vertical velocity on the diffusion-catalyst interface compared to the parallel flow field, which increases the effective concentration of reaction gases within the catalyst layer, thereby accelerating the electrochemical reaction rate, and the performance of the combined flow fields is further improved. In addition, the effect of the percentage of annular serpentine within the combined flow field on the concentration distribution, uniformity, and output performance is analyzed. Results indicate that increasing the percentage of annular serpentine structure can increase the pressure between adjacent channels, and thus the higher pressure and concentration gradient generated can enhance the gas transport and reduce the water accumulation under the ribs thus effectively improving the cell performance.

In this study, we developed a new technique, simultaneous foam electrospinning and electrospraying (FE/E), that produces nanofiber/nanoparticle electrodes at higher production rates compared to needle-based electrospinning and electrospraying (E/E). Herein, the nanofiber amount was precisely controlled by applying various voltages on the foam electrospinning process at a fixed platinum (Pt) loading, which enables an exclusive investigation into the impact of ionomer nanofiber on fuel cell performance at ultra-low Pt loadings for proton exchange membrane fuel cells. The results show that fuel cell performance is strongly dependent on ionomer nanofiber content. At 0.04 mg/cm² nanofiber amount, the electrodes exhibited the highest fuel cell power density of 1.09 W/cm² and Pt utilization of 11.5 kW/g_Pt, which are 28% and 39% higher than those of the electrode produced via electrospraying alone, respectively. The improvement results from enhanced proton and gas transport stemming from the nanofiber network as verified by cyclic voltammetry, electrochemical impedance spectroscopy, and oxygen gain voltage analysis. The FE/E technique provides a pathway to produce ultra-low Pt nanofiber/nanoparticle electrodes at high production rates and high fuel cell performance.