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Determination of Efficiency of Tantalum and Hafnium Membranes on Fuel Cell Excha

"Determination of Efficiency of Tantalum and Hafnium Membranes on Fuel Cell Exchange Membranes"


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Figure 1 (a) Serpentine flow pattern (b) Bio-inspired flow pattern

 

The serpentine channel has only one channel and needs to drain the remaining water and impurities. However, the fluid must travel a long distance, resulting in pressure loss between the flow inlet and outlet, creating an uneven distribution in the gas diffusion layer (GDL). The biologically inspired mode seeks to improve energy efficiency without incurring higher pressure losses than the serpentine mode.

Figure 2 shows the X-ray diffraction characterization results of HfC and TaC coatings deposited on Nafion composite films. Today, coatings are made into weak layers, but it retains their properties. The crystal structures of the HfC and TaC coatings were obtained by XRD, Figure-2(a) and Figure-2(b) show the X-ray images, respectively, and the crystal structure of the HfC coating shown in Figure-2(a) shows The presence of HfC, with uniformity at 33.571, crystal plane (111) at 70.25, and cubic structure and orientation at (222). Figure 2(b) shows the diffraction pattern of the TaC sample. Crystallographic phases were identified at 40.48 tetragonal (020) and 34.87, 59.01 and 69.33 cubic structures based on the crystal planes (111), (022) and (113), respectively.

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Figure 2 X-ray diffraction patterns of (a) HfC and (b) TaC films

 

The micrographs obtained by atomic force microscopy are observed in Figure 3(a) and Figure 3(b), which show the surface characterization of the hafnium carbide samples, where the characterized surface shows Terrain inhomogeneity.

Regarding the photomicrograph corresponding to tantalum carbide, a value of 30.3 nm was obtained, which is a smoother surface and this region allows to indicate that the energy distribution is homogeneous. As far as the surface is concerned, the TaC coating exhibits the easiest response as this is a stronger bond.

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Figure 3 AFM images of (a) HfC and (b) TaC coatings

 

In Figure 4, a Nyquist plot is shown. For cells in which the HfC and TaC films are in thin film form, four resistive and three constant-phase elements are observed, and these parameters are calculated from the equivalent circuit in Figure-5. The values of each element are detailed in Table 1. Rp is the concentration of ions present in the cell. Its value is lower because the evaluation temperature is 25°C. R1 is related to the resistance of the proton membrane and plate. R2 is related to the load transfer resistance of the anode, which involves the transfer resistance of hydrogen or the oxidation reaction. R3 is related to the load transfer resistance of the cathode, where oxygen reduction takes place.

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Figure 4 Nyquist plots of HfC and TaC coatings

The carbide-based hydrogen production cathode efficiency is obtained by the equivalent circuit parameters, so it is determined that TaC yields higher performance than HfC. These results were obtained by connecting the cell to the gas flow so that the membrane has permanent ion channels and a hydration process occurs.

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Figure 5 Equivalent circuit

 

Table 1 Parameter values of equivalent circuit components of HfC and TaC coatings

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The simulated computer model provided the current density distribution, the fluid distribution throughout the flow channel, and the serpentine pattern and pressure drop of the biological inspiratory flow, and changed the electrolyte between Nafion, HfC, and TaC. Fluid (Figure 6 and Figure 7a) and pressure drop (Figure 6 and Figure 7b) varied between the two proposed modes, but did not show significant changes with electrolyte changes.

 

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Figure 6 Results of the serpentine structure (a) distribution of fluid in the flow channel, (b) pressure loss

 

The main improvement was obtained by changing the membrane, maintaining the pressure drop across the membrane, but with a considerable increase in current density for both flow modes. The pressure loss of hafnium carbide remains unchanged, but the current densities for the serpentine and bioexcited modes are increased by 10.9% and 10.6%, respectively. Figure 9(b) shows a 7.8% increase in the current density larger than that of the serpentine pattern. As shown in Figure 10, TaC is the best performing electrolyte, with a 15.4% improvement in energy efficiency for serpentine and a 15.3% improvement in biostimulated mode.

 

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Figure 7 Bio-inspired model (a) distribution of fluid in the flow channel, (b) pressure loss

 

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Figure 8 Current density, serpentine, bio-inspired mode using Nafion as electrolyte

 

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Figure9 Current density, serpentine with HfC as electrolyte

 

Biostimulation mode Overall, the biostimulation mode and the new membrane material reflect a significant improvement in fuel cell energy efficiency. Some modifications to the biostimulated flow can be made to reduce pressure losses, including parallel paths for a more uniform distribution. Figure 11 provides a visualization of the data obtained from the simulation.

 

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Figure 10 Current density, serpentine, and bio-inspired modes using TaC as electrolyte

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Figure 11 Current density in different fuel cell configurations