Fuel Cells最新文献

Hierarchically oriented macroporous NiO–BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY7) anode-supporting layer (ASL) was developed using the freeze casting technique. The resulting freeze-cast structure was analyzed through scanning electron microscopy and X-ray computed tomography. A thin layer of BZCY7 was utilized as a proton-conducting electrolyte, whereas La_1.9Sr_0.1Ni_0.7Cu_0.3O_3−δ –gadolinium-doped ceria 10% Gd (LSNC–GDC10) was employed and evaluated as cathode layer. The performance of the cell was assessed by means of electrochemical impedance spectroscopy and I–V–P curves at various temperatures. Furthermore, as a point of comparison, a cell with an ASL was prepared using the dry pressing method, incorporating 20 wt.% graphite as a pore-forming agent. The freeze-cast anode-supported cell demonstrated a polarization resistance of 1.45 Ω cm² at 550°C and 0.29 Ω cm² at 750°C. Maximum achieved power densities were 0.189 and 0.429 W cm⁻² at 550 and 750°C, respectively. For the cell fabricated by the dry pressing method, the maximum power densities were 0.158 and 0.397 W cm⁻² at 550 and 750°C, respectively. Additionally, the tortuosity factor of the anode layer and the gas diffusion streamline in the direction of solidification were determined by using 3D X-ray tomography imaging and subsequent image processing.

Durability of membrane electrode assembly (MEA) is a serious problem to be overcome in the commercial development of proton exchange membrane fuel cell (PEMFC). The change in volume due to water–ice conversion has an irreversible effect on the MEA, which affects the performance of PEMFC. For investigating the optimal initial water content of MEA that minimizes the impact on PEMFC performance after freeze–thaw (F/T) cycles, this study first measured the high-frequency resistance to determine the water content of MEA, and then subjected five MEAs with different water contents to 60 F/T cycles at −20°C to 30°C. The fuel cell output performance of five MEAs was found to be inconsistently degraded by polarization curve tests, with the cells of the two MEAs with the lowest and highest water contents exhibiting the worst output performance. Electrochemical impedance spectroscopy curves proved that the difference in resistance change after F/T cycles is one reason why the cell output performance is degraded differently. Finally, the degradation of cell performance was further explained by cyclic voltammetry. These results indicate that MEA has the best output performance for F/T cycles at an initial water content of 3.0.

Polymer electrolyte membrane fuel cell durability is still a major challenge. To overcome time-consuming durability tests, so-called accelerated durability tests (ADTs) are of urgent need. This work presents our recent results in developing ADT protocols in the context of realistic operating conditions, especially voltage clipping at 0.85 V. A 5500 h long-term test was carried out as a reference applying a realistic automotive drive cycle. Focusing on different stressors such as temperature, relative humidity (RH), and load profile four different ADT protocols of 1200 h duration were derived. Seven-cell short stacks with 240 cm² active area were used. Comparing cell voltage as a key indicator, an acceleration factor of 3–7 could be achieved. In-situ characterization techniques such as spatially resolved current measurement, cyclic voltammetry, and electrochemical impedance spectra were employed to investigate the influences of individual stressors on specific degradation mechanisms and components. The highest acceleration was observed in the mass transport region of ADTs addressing RH as a stressor, suggesting that RH cycling leads to increased degradation of hydrophobic surfaces. Increased temperature was found to accelerate primarily carbon support degradation. Accelerated catalyst aging seems to be low, demonstrating the effectiveness of voltage-clipping conditions. Our most promising ADT shows quite a homogeneous acceleration of voltage degradation across all current regions.

Proton exchange membrane fuel cells (PEMFCs) as power generators and proton exchange membrane water electrolyzers (PEMWEs) as hydrogen fuel producers play critical roles in implementing hydrogen energy. The bipolar plates (BPPs) in both PEMFC and PEMWE facilitate the distribution of reactants and products, providing electrical connectivity in a series of singular cells. Although both systems are categorized under the same PEM spectrum, the differing reaction mechanisms require specialized plate properties to achieve optimum performance. This short review analyzes the characteristics of BPPs in both PEMFC and PEMWE, with a focus on the plate material, coating, and flow field. This short review concluded that the polymer composite graphite–based BPPs are the most feasible for PEMFC with no coating needed. PEMWE needs SS316 as a BPP material with a conductive coating to withstand the highly corrosive oxygen evolution reaction at the anode. The serpentine flow field showed dominance in PEMFC stack performance due to even fluid distribution and efficient liquid water drainage. However, its high-pressure drop contributes to greater parasitic power. PEMWEs commonly adopt the parallel flow field for its lower contact resistance and bubble formation for efficient mass transport toward the cathode.