Fuel Cells最新文献

Some of the most popular technologies for wastewater sanitation, still face serious limitations related to high energy consumption requirements. In this context, microbial fuel cells (MFCs) constitute a promising approach since they do not require aeration and produce electricity at the same time. Limitations for these devices, however, are related to the cost of the constituents and the functionality of the arrangement. In this work, a semi-cylindrical ceramic MFC was designed and constructed using a low-cost commercial ceramic handcraft as a membrane, carbon felt, carbon cloth, and carbon cloth/activated carbon in different arrangements for the anode and cathode components. The best results were obtained using carbon felt as an anode and a cathodic zone built with carbon felt in which void regions were filled with activated carbon. This arrangement produced 85 mWm⁻² for each cell. Evaluating the performance of the MFC in a modular system with eight cells using a different number of separations inside the module and different electrical connections, resulting in a 4-compartment module that produced 90 mWm⁻² with one single module and 95 mWm⁻² with a serial arrangement of two modules.

Direct methanol fuel cells (DMFCs) have received a lot of attention in recent years as promising technology for generating clean and efficient energy. In DMFC, the anode catalyst is a vital component because it is involved in the oxidation of methanol, which produces electrons that can be used as an energy source. Cyclic voltammetry (CV) is commonly used to test the characteristics of the electrode materials before they are employed in the actual fuel cell. Interestingly in the case of DMFCs CV also is a useful technique to obtain vital information about the performance and expected efficiency of the electrodes. In general, the CV of methanol electrooxidation for Pt-based catalysts has two peaks, I_f in the forward scan (anodic scan) and I_b in the backward scan (cathodic scan). The ratio of these two peaks (I_f/I_b) is the most commonly used criterion for investigating CO poisoning in catalysts. However, there is a great deal of ambiguity surrounding this criterion, owing to the genesis of I_b. Addressing this we present here a new criterion to evaluate the efficiency of the catalyst using the same CV technique. We validate this newly proposed criterion with commercial Pt/C (comm. Pt/C) and other commercially available alloy catalysts.

In this study, Pd/TiO₂ decorated carbon nanofibers (Pd/TiO₂@CNFs) and Pd@CNFs were prepared by the impregnation method for application in direct methanol fuel cells (DMFCs). Pd and TiO₂ particles were supported on the surface of carbon fibers. Noticeably, When the mass fraction of PdCl₂ added is 4%, the Pd@CNFs catalyst (Pd-4@CNFs) showed higher electrocatalytic activity and stability, which were about 28.4 and 13.2 times higher than those of commercial Pd/C catalyst, respectively. On the basis of Pd-4@CNFs catalyst, TiO₂ with a mass fraction of 10% was added to produce Pd/TiO₂@CNFs catalyst (Pd-4/TiO₂-10@CNFs). The electrocatalytic activity of Pd-4/TiO₂-10@CNFs increased to 3,850.4 A·g⁻¹, which was 31.9 times higher than that of commercial Pd/C catalysts. These results demonstrated that the novel Pd/TiO₂@CNFs catalyst is expected to be an efficient and durable catalyst for DMFC.

Bipolar plates are the key component in polymer electrolyte membrane fuel cells (PEMFCs), which ensure the low cost of the fuel cell stack and furnish some of the important applications such as distributing the reactant gases, conducting the electrons, and removing the waste heat in PEMFCs. Thus, metallic bipolar plates (BPs), such as aluminum (Al), have attracted immense consideration and afford better performance in different machine-driven applications and mass manufacturing opportunities. In order to increase the corrosion resistance of Al BPs, several methods are used and conducted by scientists. The corrosion behavior and surface structure analysis of pure Al were studied through the immersion process in fluoride-sulfate solutions, assuming its use as BPs in PEMFC-produced water. The open cell voltage, interfacial contact resistance, and polarization tests and the fuel cell operations were performed to evaluate cell voltage, current density, corrosion resistance, and the effect of fluoride and sulfate ions on the BPs in PEMFC. The hydrophobicity character of the surface of Al BPs was observed by the measurement of the wettability test. The atomic force microscopy images were taken to study the surface roughness, which was correlated with the corrosion rates of Al BPs. In addition, the amount of corrosion was calculated after 24–120 h of immersion in fluoride-sulfate solutions. The scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy data were analyzed to investigate the surface structure, morphology, and elemental analyses. Thus, the results found in this study revealed that Al-based materials can be suitable for BPs in PEMFCs. Furthermore, it is noticed that the amount of corrosion was influenced by the presence of even a very small amount of fluoride ions present in the PEMFC environment, while it was suppressed efficiently by sulfate ions.

The gas diffusion layer (GDL), one of the essential components of the membrane electrode assembly (MEA), plays an important role in the performance of proton exchange membrane fuel cells. With respect to this essential component and its specifications, this work intends to examine the impact of GDL defects and their effects on cell performance for component quality control. To understand how GDL defect affects its performance and to what level the defect takes effect, ex situ characterization and in situ fuel cell testing are conducted by comparing pristine and defective GDLs. While ex situ GDL properties incorporate measurements of thickness, conductivity, and permeability under compression, in situ investigation mainly involves polarization curve and electrochemical impedance spectroscopy. Among different types of GDL defects, pinholes are targeted in this work. As such, the evaluation focuses on assessing the effects of varying numbers and sizes of pinhole defects under different relative humidities (RHs). Using the state-of-the-art GDLs, an improved cell performance is observed with defective GDLs (evenly distributed 40 pinholes with a diameter of 0.58 mm) under 100% RH. Results also show that the effect of pinhole defects is sensitive to RH, as well as operating current densities.

The chemical reactivity between Pr₄Ni₃O_10±δ (3-PNO) electrodes and Y_0.08Zr_0.92O_1.96 (YSZ), Ce_0.9Gd_0.1O_1.95 (GDC), and La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 (LSGM) electrolytes was analyzed by electrochemical impedance spectroscopy and X-ray diffraction. 3-PNO powders were synthesized by two different chemical routes, one of them uses hexamethylenetetramine (HMTA) as a complexing agent (route A) while the other citrates (route B). The samples observed by scanning electron microscopy presented different microstructures; route A powders present small submicronic grains with an open microstructure while route B powders are formed by larger well-connected grains. The polarization resistance (R_P) values for 3-PNO/YSZ cells are one order of magnitude higher than those of 3-PNO/GDC and 3-PNO/LSGM cells. The R_P for both cells 3-PNO/GDC and 3-PNO/LSGM and its evolution in time suggest that chemical reactivity takes place during the adhesion treatment and electrochemical measurements. The microstructure plays a crucial role in R_P and the degradation rate; 3-PNO obtained by route A (3-PNO-HMTA) exhibits the best electrochemical performance since these powders present a well-loose morphology and a large exposed area. However, this fact makes them active chemically, so the increase of R_P with time is slower for 3-PNO electrodes prepared by route B (3-PNO-Cit), since the rate of chemical reactivity with the electrolyte is slower.

In the production of catalyst-coated membranes (CCMs) for proton-exchange membrane fuel cells and electrolyzers, the ink formulation and its processing are key factors in determining the resulting catalyst layer. Catalyst inks often contain a multicomponent solvent mixture. Selective drying, which can occur with solvent mixtures, changes the composition in the solidifying film and thus influences the microstructure of the layer that forms. The selectivity depends on the material-specific thermodynamics of the solvents and the process-related drying parameters. Different 1-propanol/water mixtures serve as the state of the art material system considered and commonly used for CCM inks. Typical solvent mixtures can be dried selectively or non-selectively, depending on the initial ink composition and humidity of the drying air. In mixtures that contain more 1-propanol than the azeotropic or arheotropic composition, the 1-propanol content accumulates in the remaining liquid; if there is less, it decreases. Increasing the preloading of the drying air with water leads to a relative water enrichment and shifts the tipping point to higher initial alcohol fractions. This behavior can be transferred to the real CCM production.

In low-temperature environment, the residual water in the membrane electrode assembly (MEA) will freeze after the operation of proton exchange membrane fuel cells, which will cause damage to the MEA. In this paper, the effect of freeze–thaw cycles on MEA was studied. Six sets of MEA samples with 0, 20, 40, 60, 80, and 100 times freeze–thaw cycles were set up, and the damage on MEAs is analyzed by polarization curves, electrochemical impedance spectra, cyclic voltammetry curves, and scanning electron microscope. It was found that the freeze–thaw cycles caused degradation on MEA, and the ohmic resistance of MEA increases with the number of cycles increases before the 60 freeze–thaw cycles, and after 60 freeze–thaw cycles, a gap appeared between the proton exchange membrane (PEM) and the catalyst layer, which led to more water entering the PEM and the ohmic resistance of MEA decreased. Besides, according to the data analysis, the experimental samples are divided into three categories (normal MEA, lightly damaged MEA, and seriously damaged MEA). A classifier model combining inception network and light gradient boosting machine (LGBM) was established, and it was found that the combined model was better than inception–dense and LGBM for classification, reaching 96.89%.