# Experimental study of the effects of operating conditions on the performance and stability of a PEM fuel cell supplied with dry air analysed with a segmented cell

Djabril Mohamed, Sophie Didierjean, Jean-Philippe Poirot-Crouvezier

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Djabril Mohamed, Sophie Didierjean, Jean-Philippe Poirot-Crouvezier. Experimental study of the effects of operating conditions on the performance and stability of a PEM fuel cell supplied with dry air analysed with a segmented cell. 4ème Réunion Plénières de la Fédération Hydrogène du CNRS, Fédération de Recherche Hydrogène du CNRS (FRH2), Oct 2024, La grande Motte, France. hal-04941853

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# Experimental study of the effects of operating conditions on the performance and stability of a PEM fuel cell supplied with dry air analysed with a segmented cell

**Djabril MOHAMED**<sup>a,b</sup>, **Jean-Philippe POIROT-CROUVEZIER**<sup>a</sup>, **Sophie DIDIERJEAN**<sup>b</sup>

<footnote><sup>a</sup> Univ. Grenoble Alpes, CEA, LITEN, DEHT, 38000 Grenoble, France</footnote>

<footnote><sup>b</sup> LEMTA, CNRS, Université de Lorraine, 54000 Nancy, France</footnote>
# HYSYSPEM project : Simplify PEMFC systems

The European Union has set a target of reducing emissions from heavy duty vehicles by **45%** by **2030**.

The **HYSYSPEM** project involves the design of a hybrid fuel cell system:

* Modular multi-stack

* High-power application

* Simplified architectures

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## HYDROGEN FUEL CELL SYSTEM

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**Objective:** Experimental study of the impact of dry air supply on a fuel cell.

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# SUMMARY

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## Instrumented single-cell study

1. Experimental bench & protocol

2. Experimental results

3. Specific features of dry air operation
# Experimental tool: Segmented cell

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<table><thead><tr><th colspan="2">Characteristics of the segmented cell</th></tr></thead><tbody><tr><td>Active surface area</td><td>30x1 cm²</td></tr><tr><td>Segments</td><td>20</td></tr><tr><td>Membrane</td><td>Nafion XL</td></tr><tr><td>Electrode loading (mg/cm²)</td><td>0,1 anode<br>0,3 cathode</td></tr><tr><td>Flow configuration</td><td>counter-current</td></tr></tbody></table>

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T. Schmitt, « Method development and experimental investigation of dynamic water distribution in a segmented PEMFC », Energy and Mechanics, Université de Lorraine, Vandoeuvre-lès-Nancy, 2023.

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# Presentation of the experimental bench

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## Operating parameters

Gas stoichiometry

Gas humidity

Pressure

Temperature
# Parameters of the experimental campaign

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**Objective:** compare operation with dry air supply and with wet air supply on 3 aspects

## Stability

30 min steady-state tests

* Current profile study

* Determining the stability of the operating point

## Performances

Polarisation curve

<figure><img src="image_12.png" /></figure>

## Humidification

Electrochemical Impedance Spectroscopy (EIS)

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<table><thead><tr><th>Parameters</th><th>Temperature (°C)</th><th>Total pressure (Bars)</th><th>Air stoichiometry (-)</th><th>H<sub>2</sub> stoichiometry (-)</th><th>Air humidity (%)</th><th>H<sub>2</sub> humidity (%)</th></tr></thead><tbody><tr><td>Reference parameters</td><td>70</td><td>1,5</td><td>2</td><td>1,2</td><td>50</td><td>50</td></tr><tr><td>Study range</td><td>60-80</td><td>1,5-3</td><td>1,5-3</td><td>1,2-2</td><td>0 or 50</td><td>30-60</td></tr></tbody></table>

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# Experimental protocol

<table><thead><tr><th>Step</th><th>Current set point</th><th>Humid 50% RH</th><th>Dry 0% RH</th></tr></thead><tbody><tr><td>1</td><td>0,2 A/cm²</td><td>EIS</td><td>EIS</td></tr><tr><td>2</td><td>0,5 A/cm²</td><td>EIS I-V</td><td>EIS I-V</td></tr><tr><td>3</td><td>1,2 A/cm²</td><td>EIS</td><td>EIS</td></tr><tr><td>4</td><td colspan="3">Idem Step 2</td></tr><tr><td>5</td><td colspan="3">Idem Step 1</td></tr></tbody></table>

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30min steady-state

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Electrochemical
Impedance Spectroscopy

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Polarisation curve

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08/10/2024
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# Influence of air stoichiometry

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* Performance increases with air stoichiometry for the humid case

* Performance strongly decreases with air stoichiometry for the dry case

* Increased flow of dry air **dries out the membrane**

<table><thead><tr><th>Temperature (°C)</th><th>Pressure anode (Bar<sub>abs</sub>)</th><th>Pressure cathode (Bar<sub>abs</sub>)</th><th>Air stoichiometry</th><th>H2 stoichiometry</th><th>Air humidity (%)</th><th>H2 humidity (%)</th></tr></thead><tbody><tr><td>70</td><td>1,5</td><td>1,5</td><td>1,5-3</td><td>1,2</td><td>0 & 50</td><td>50</td></tr></tbody></table>

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# Influence of pressure

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* Performance **increases** with pressure

* Increased pressure **reduces the difference** between the dry and wet cases

→ **Relative humidity increase** with pressure

$$RH = \frac{x_{H_2O} \times P_{tot}}{P_{sat}(T)}$$

<table><thead><tr><th>Temperature (°C)</th><th>Pressure anode (Bar<sub>abs</sub>)</th><th>Pressure cathode (Bar<sub>abs</sub>)</th><th>Air stoichiometry</th><th>H<sub>2</sub> stoichiometry</th><th>Air humidity (%)</th><th>H<sub>2</sub> humidity (%)</th></tr></thead><tbody><tr><td>70</td><td>1,5-3</td><td>1,5-3</td><td>2</td><td>1,2</td><td>0 & 50</td><td>50</td></tr></tbody></table>

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# Influence of temperature

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* Performance **decreases** with temperature for dry case

* Decrease temperature **reduces the difference** between the dry and wet cases

→ **Relative humidity decrease** with temperature

$$RH = \frac{x_{H_2O} \times P_{tot}}{P_{sat}(T)}$$

<table><thead><tr><th>Temperature (°C)</th><th>Pressure anode (Bar<sub>abs</sub>)</th><th>Pressure cathode (Bar<sub>abs</sub>)</th><th>Air stoichiometry</th><th>H2 stoichiometry</th><th>Air humidity (%)</th><th>H2 humidity (%)</th></tr></thead><tbody><tr><td>60-80</td><td>2</td><td>2</td><td>2</td><td>1,2</td><td>0 & 50</td><td>50</td></tr></tbody></table>

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# Stability study – current profile with **dry air**

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<figure><img src="image_44.png" /><figcaption>Stable</figcaption></figure>

<figure><img src="image_45.png" /><figcaption>Segment (-)</figcaption></figure>

$$P=2 \text{ bars } \& \ k_{\text{air}}=2$$

<figure><img src="image_46.png" /><figcaption>Stable degraded</figcaption></figure>

<figure><img src="image_47.png" /><figcaption>Segment (-)</figcaption></figure>

$$P=1,5 \text{ bars } \& \ k_{\text{air}}=2$$

<figure><img src="image_48.png" /><figcaption>Unstable</figcaption></figure>

<figure><img src="image_49.png" /><figcaption>HFR per segment</figcaption></figure>

<figure><img src="image_50.png" /><figcaption>HFR per segment</figcaption></figure>

<figure><img src="image_51.png" /><figcaption>HFR per segment</figcaption></figure>

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08/10/2024

4th FRH2 Meeting - La Grande Motte, France - 7 to 11 October 2024
30min

# Stability - Dependence on operating history

<figure><img src="image_53.png" /><figcaption>Current set point: 0,5 A/cm²</figcaption></figure>

<figure><img src="image_54.png" /><figcaption>Current profile for step 4</figcaption></figure>

<table><thead><tr><th>Temperature (°C)</th><th>Pressure anode (Bar<sub>abs</sub>)</th><th>Pressure cathode (Bar<sub>abs</sub>)</th><th>Air stoichiometry</th><th>H2 stoichiometry</th><th>Air humidity (%)</th><th>H2 humidity (%)</th></tr></thead><tbody><tr><td>70</td><td>1,5</td><td>1,5</td><td>2</td><td>1,2</td><td>0</td><td>50</td></tr></tbody></table>
30min

# Performance comparison between dry and wet cases

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higher performance
**humidified** air supply

$$ \text{Relative difference} = \frac{U_{\text{humid}} - U_{\text{dry}}}{U_{\text{humid}}} \times 100 $$

higher performance
**dry** air supply
# Humidification - Current density dependency

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Humidified zone

Dry zone
# Conclusions & perspectives

Experiments have shown that it is possible to ensure **stable and high-performance** operation of the cell when it is supplied **with dry air**

→ **Operating parameters** need to be adjusted :

☐ **High pressure** helps to saturate the gases with moisture from the water produced inside the cell.

☐ **Low air stoichiometry** facilitates dry operation by reducing membrane drying.

☐ **Increase hydrogen stoichiometry and relative humidity** improves the hydration of the membrane by the anode, which favors operation with dry air.

☐ **Low temperature** helps to saturate the gases with moisture from the water produced inside the cell.

→ Ageing tests will allow to determine whether operating with a dry air supply has an **impact on the durability** of the cell.

→ Tests with **another MEA** and **modelling** work will complete the study.

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Thank you

The authors acknowledge support from the French National Research Agency (ANR) under France 2030 program

Reference ANR-22-PEHY-0018 (project PEPRH2-HYSYSPEM)

Contact:

Djabril.mohamed@cea.fr

UGA
Université
Grenoble Alpes

UNIVERSITÉ
DE LORRAINE

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PROGRAMME
DE RECHERCHE
HYDROGÉNE

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INSTITUT
CARNOT
Energies du Futur