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# Improved operating strategies of PEMFC system

Guillaume Soubeyran, Magali Reytier, Fabrice Micoud, Jean-Philippe Poirot

► To cite this version:

Guillaume Soubeyran, Magali Reytier, Fabrice Micoud, Jean-Philippe Poirot. Improved operating strategies of PEMFC system. Journal of Power Sources, 2023, 597, pp.234089. 10.1016/j.jpowsour.2024.234089. cea-04471441

HAL Id: cea-04471441

https://cea.hal.science/cea-04471441v1

Submitted on 21 Feb 2024

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# Improved operating strategies for the optimization of PEMFC system performance

G. Soubeyran, F. Micoud*, B. Morin, M. Reytier, J. Poirot-Crouvezier

Univ. Grenoble Alpes, CEA, Liten, 38000, Grenoble, France

## HIGHLIGHTS

* Platinum oxidation during nominal operation leads to reversible performance loss.

* Short and periodic recovery phases enable higher cell voltage in operation.

* Both direct air starvation and air dilution improves performances in a stack.

* This study optimizes the application of recovery procedures for PEMFC operation.

## ARTICLE INFO

**Keywords:**

Durability

PEMFC

Recovery procedure

Reversible degradations

Efficiency

## ABSTRACT

The formation of platinum oxides at PEMFC working cathode potential is one of the main sources of reversible performance loss during operation as this mechanism passivates active surface. Therefore, promoting the electrochemical reduction of these oxides during operation is a solution to increase performance and mitigate reversible losses related to this phenomenon. Thus, a feasible solution to achieve this result in a PEMFC stack and system is to apply frequent and short operating phases with reduced air supply at the cathode. This procedure, called "air starvation" enables the decrease of cathode potential from nominal potential to approximately 0 V vs. RHE, promoting the electrochemical reduction of platinum oxides. This study focuses on the optimization of recovery parameters, first at small single cell scale and then at short-stack scale with air starvation procedure.

## 1. Introduction

Proton Exchange Membrane Fuel Cells (PEMFC) is one of the most interesting technology to replace combustion engines in heavy-duty transportation. However, some challenges must be resolved before mass usage. Maintaining high cell performance over time is one of the major issues to address in order to enable PEMFC technology to be competitive in transport applications. Many studies have been carried out on PEMFC degradations to mitigate their effect on stack durability [1,2]. Some of these degradations are irreversible because they arise from the physical alteration of PEMFC components of the Membrane Electrode Assembly (MEA), caused by mechanical [3], chemical [4,5], and electrochemical phenomena [6,7]. These degradations lead to continuous and definitive performance loss. However, other MEA degradation processes are reversible. That means that if specific conditions are applied, these performance losses could be partially or totally recovered. Reversible degradations mainly consist of three different

factors: variation of the hydration within the membrane/ionomer (drying and flooding) [8], carbon monoxide poisoning at the anode under nominal operation with pure H₂ [9,10], and platinum oxidation at the cathode [11] when cathode potential is superior to ca 0.6 V. The latter mechanism is identified as a major contributor to reversible performance loss at the cathode [12] since high cathode potential induces the partial passivation of active sites for Oxygen Reaction Reduction (ORR) occurring at the cathode.

Platinum passivation is both linked to time and potential [13]. It ultimately leads to cathode active surface diminution, thus decreasing the overall cell electrochemical performance. Reversing this passivation requires a recovery procedure based on the periodic electrochemical reduction of these oxides. In the literature, this strategy has been studied and several methods were used to recover this type of reversible degradation in most cases after several hours of operation. A first method is to apply high current densities under nominal operating conditions to naturally decrease the cell potential down to ca 0.5 V. Such

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: fabrice.micoud@cea.fr (F. Micoud).</footnote>
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solution is not always optimized for PEMFC system due to the important heat production, the high H₂ consumption and the low efficiency of such recovery procedure as shown by Zago et al. [14]. Other recovery procedures consist mainly in suppressing air supply at the cathode whether by reducing [15], by stopping air flow [14,16], or by directly purging the cathode with nitrogen [17]. Chu et al studied long-term effect of platinum oxides reduction on 3-cell stack by injecting fully humidified nitrogen while maintaining 2 A (corresponding to 0.006 A cm⁻²) load [18] after an operating phase based on normalized Fuel Cell Dynamic Load Cycles (FC-DLC) used for testing of PEMFC systems in automotive applications. The study shows that such procedures can recover up to 50 mV for cell voltage even after 600 h in operation. Another study of Colombo et al. [19] on single cell also showed that stopping stack operations while keeping constant hydrogen flowrate could have a benefit of up to 20 mV on mean cell voltage. Nevertheless, such repeated variation of platinum potential could also affect irreversible degradation by increasing platinum dissolution [20–22]. Moreover, cell voltage below 0.5 V promotes the generation of hydrogen peroxide at the cathode due to the reaction [1]:

$$O_2 + 2H^+ + 2e^- \leftrightarrow H_2O_2 \text{ with } E^0 = 0.695 \text{ vs RHE} \quad (1)$$

Hydrogen peroxide then generates radicals that ultimately damage either the membrane or the ionomer and carbon support in the active layer [23,24]. Maas et al. [25] indeed showed that rate of carbon corrosion and fluoride release is aggravated below 0.3 V presumably as a result of these mechanisms. Another source of irreversible degradation is linked to current and temperature heterogeneities induced during the air starvation phase as the ORR reaction is concentrated at the air inlet as simulated and measured by Gerard et al. [26]. They studied the application of 5 s air starvation phase every minute and observed a degradation rate more than seven times superior to nominal degradation rate in a 200-h period at stack level. Therefore, it is critical to find the correct balance between the mitigation of irreversible degradation and the optimization of performance by the recovery of reversible losses.

Still the use and the optimization of periodic recovery procedures during operation to increase stack performance has been poorly studied so far. To our knowledge, only two main studies can be mentioned. Firstly, Decoopman et al. [11] have tested periodic recovery by air swing in single cell. This operating mode consists in periodic air flowrate inversion as humidification strategy, causing air starvation phases during operation every 20 s. This strategy yields to an increase of approximately 35 mV at 0.5 A cm⁻² in nominal conditions. Secondly, Colombo et al. [19] have tested periodic recovery by stopping air flow during accelerated stress test (AST) procedures until cell voltage reached a chosen value. No voltage increase caused by this short-stops is however mentioned in this work.

This study focuses first on evaluating the effectiveness of recovery procedure application from model 1.8 cm² single cell set-up and then to adapt and apply them at PEMFC short-stack level (98 cm²) to find the best operating parameters in terms of cell potential, recovery duration and the most suitable air starvation methodology. In addition to cell performance, we assess the effectiveness of the different recovery procedures based on the hydrogen efficiency, which is more relevant at PEMFC system level than considering solely cell voltage gain.

## 2. Experimental

### 2.1. Components and operating conditions of differential cell

Differential cells are very small single cells (1.8 cm²) in which high cathode and anode flowrates are applied. The objective of using differential cell is to discriminate raw electrochemical performance from fluidic and thermic variations in the cell. Thus, operating conditions are precisely controlled and homogeneous during use. Cell operating conditions are detailed in Table 1.

<table><caption>**Table 1**
Test operating parameters.</caption><thead><tr><th>Operating parameters</th><th>Differential cell</th><th>Stack A</th><th>Stack B</th></tr></thead><tbody><tr><td><strong>General</strong></td><td></td><td></td><td></td></tr><tr><td>Coolant temperature (°C)</td><td>80 (homogeneous)</td><td>82 (stack outlet)</td><td>82 (stack outlet)</td></tr><tr><td>Pressure (bara)</td><td>1.5</td><td>1.5</td><td>1.5</td></tr><tr><td>Number of cells</td><td>1</td><td>4</td><td>6 (equipped with S++® device between cell 3 and 4)</td></tr><tr><td>Active surface (cm²)</td><td>1.8</td><td>98</td><td>98</td></tr><tr><td><strong>Break-in procedure</strong></td><td></td><td></td><td></td></tr><tr><td>Air stoichiometry</td><td>25 at 2 A cm<sup>-2</sup> (constant flowrate)</td><td>2</td><td>2</td></tr><tr><td>Hydrogen stoichiometry</td><td>20 at 2 A cm<sup>-2</sup> (constant flowrate)</td><td>1.5</td><td>2</td></tr><tr><td>Relative humidity (%)</td><td>80</td><td>80</td><td>80</td></tr><tr><td><strong>Nominal conditions</strong></td><td></td><td></td><td></td></tr><tr><td>Air stoichiometry</td><td>25 at 2 A cm<sup>-2</sup> (constant flowrate)</td><td>2</td><td>2</td></tr><tr><td>Hydrogen stoichiometry</td><td>20 at 2 A cm<sup>-2</sup> (constant flowrate)</td><td>1.5</td><td>2</td></tr><tr><td>Relative humidity (%)</td><td>80</td><td>50</td><td>50</td></tr><tr><td><strong>During recovery phase</strong></td><td></td><td></td><td></td></tr><tr><td>Air stoichiometry</td><td>Unchanged</td><td>0.8 (direct starvation), 1.3 (air dilution)</td><td>0.8 (direct starvation), 1.1 (air dilution)</td></tr><tr><td>Oxygen molar fraction during air dilution phases</td><td>Unchanged</td><td>6 %</td><td>7 %</td></tr><tr><td>Hydrogen stoichiometry</td><td>Unchanged</td><td>1.5</td><td>2</td></tr></tbody></table>

All experiments use commercial Catalyst Coated Membrane (CCM) with a Pt loading of 0.4 mg cm⁻² at the cathode and 0.1 mg cm⁻² at the anode and state-of-art PFSA-based membrane (15 µm thick), assembled with commercial GDL (SGL Sigracet 22BB). The combination is inserted in a CEA-made 1.8 cm²-differential cell (1.2 cm × 1.5 cm as active area) using a fine flow-field design integrated in monopolar plates (250 µm/ 250 µm rib/channel width and 400 µm depth) at both anode and cathode sides (Fig. 1 a.).

Differential cell are subject to a CEA-patented break-in procedure [27] in order to have stable performance during nominal operations prior to any tests and characterizations. This 20-min procedure consists in applying potentiostatic operations at 0.1 V in nominal operating conditions detailed in Table 1 with diluted air (5 % O₂).

### 2.2. Experimental setup and protocol at differential cell level

Differential cells are tested on a Fuel Con test bench (Evaluator-C 70351). A Fisherbrand thermoregulator (Polystat R4/37/866 2R) with deionized water controls single cell temperature. Consequently, such high flowrate makes possible a homogeneous temperature within the differential cell for any current density set point used in this work. Electrochemical measurements are carried out with a Biologic potentiostat (VMP2 with 10 A Booster WMP38-10). EC-Lab software is used to gather data and supervise electrical parameters. Gas inlets are connected on top of the cell and pre-heated to avoid any condensation of water. Gases are then evacuated at the bottom of the cell to prevent liquid water accumulation. Relative humidity is controlled by bubblers of the test bench.
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<figure><img src="image_2.png" /><figcaption>Fig. 1. Disassembled view of a) Differential cell with 1.8 cm² active area and b) Scheme of short-stack with 4 cells and equipped with S++® device.</figcaption></figure>

## 2.3. Experimental setup and protocol at short-stack level

Experiments in short-stacks are carried out by using a CEA-stack technology with 98 cm² active surface area and linear flow field design as already used in previous work [28]. Two different short-stacks are tested with respectively two different commercial Membrane Electrode Assemblies (MEAs) both composed of Pt/C catalyst with platinum loading of respectively 0.4 mg/cm² at the cathode and 0.1 mg/cm² at the anode. Stack A is assembled with four cells whereas Stack B is assembled with six cells from another MEA supplier (but with the same

Pt loadings). The latter is equipped with a commercial local current measurement device (S++®) already used in previous work [29] that is inserted between the 3rd and 4th cell (Fig. 1 b.). This device is divided into 13x13 isolated segments (~0.58 cm² each) sampled with a frequency up to 3 Hz. Operating conditions are summarized in Table 1. It is worth pointing out that hydrogen stoichiometry is increased from 1.5 to 2 to mitigate cell flooding within the stack B. This change is expected to be negligible on the overall electrochemical performance and general behavior during nominal and specific recovery phases. In addition, to experimentally limit the temperature difference at approximately 2 °C at

<figure><img src="image_3.png" /><figcaption>Fig. 2. voltage (a) and current density (b) evolution during one operating cycle including 1 s recovery phase (detailed operating conditions in Table 1) c) and d) zoom on respectively cell voltage and current density around recovery phase.</figcaption></figure>
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1 A cm⁻², the coolant flowrate through the stack is set to 0.5 L min⁻¹ cell⁻¹.

Both short-stacks are tested using a commercial test bench Green-light equipped with Dynaload electronic load (XBL 50-400-2000 model). The operating conditions are controlled by the HyWare II software and the typical response time, a key parameter for applying short air starvation phases, is between 0.5 and 1 s to reach the flow set point.

Both short-stacks are subject to a break-in procedure (Table 1) in order to have stable performance during nominal operations prior to any tests and characterizations. This 8-h break-in procedure consists in applying 1 A cm⁻² current density set point in conditions detailed in Table 1 at the exception of relative humidity that is set to 80 % for both anode and cathode gas.

## 2.4. Analysis of recovery effectiveness

### 2.4.1. Recovery cycle

In this work, we are defining an "operating cycle" as the combination of one galvanostatic operating period under nominal conditions during typically 10 min followed by a potentiostatic operating phase from 1 to 9 s where voltage is set below 0.5 V. Fig. 2 shows two examples with a nominal period of 10 min and a recovery phase of 1 s. They differ only in the voltage reached during the recovery phase, which is either 0.2 V or 0.0 V. Nominal current density is set at 0.8 A cm⁻² corresponding to an operating mean cell voltage close to 0.7 V. Recovery phase is then applied by imposing a low voltage (Fig. 2 a.) and consequently a high current density (Fig. 2 b. and d.) to promote the electrochemical reduction of platinum oxides yielding to cell performance recovery. Immediately after the recovery phase, cell potential increases by ca. 50 mV. After reaching this peak, cell voltage progressively decreases by ca. 40 mV after 1 min of operation, 47 mV after 5 min of operation and ca. 50 mV after 10 min of operation.

### 2.4.2. Calculation of hydrogen efficiency and application to recovery phases at differential cell scale

To assess the effectiveness of different recovery phases performed on 1.8 cm² single-cell but considering overall operating conditions at PEMFC system scale, several assumptions have to be made to adapt and to simulate a stack undergoing an equivalent air starvation phase:

- Current density during recovery is artificially limited to 1 A cm⁻². In our experiments with differential cell, constant and high H₂/air flowrates and small cell active area of 1.8 cm² lead to current densities increasing up to 5 A cm⁻² during the recovery phase. However, such current density would be misleading as this value would not be achievable in a PEMFC system due to practical limitation of H₂/air flowrate. Moreover, it would generate excessive heat compared to the cooling capacity and would therefore damage the cell. In such conditions, a maximum and global current density of approximately 1 A cm⁻² in our stack technology may be expected during air starvation period rather than the real hydrogen consumption at differential cell.

- System output power during recovery phase is equal to zero. Indeed, electric converters of a PEMFC system are usually not adapted to low voltages. Therefore, electrical energy output during the recovery phase is not taken into account but hydrogen consumption, calculated with the simulated current mentioned previously, must be nevertheless considered as an input.

- Due to purges at the anode, some hydrogen is lost. In the literature, a 1 % H₂ loss is usually considered [30]. Therefore, hydrogen system stoichiometry vH₂ is set at 1.01.

Based on these assumptions, the effectiveness of recovery phases can be calculated for each operating cycle. Hydrogen Efficiency (ρH₂) is obtained by Equation [2] for each recovery cycle starting at t₀:

$$ \rho_{H2} = \frac{\int_{t_0}^{t_0 + \Delta t_{nominal}} \text{Power}}{\Delta H_{LHV} \times v_{H2} \times F_{H2_{nominal}} \times \Delta t_{nominal} + \Delta H_{LHV} \times v_{H2} \times F_{H2_{recovery}} \times \Delta t_{recovery}} \quad (2) $$

Hydrogen consumption FH₂ (mol s⁻¹) during nominal and recovery phase is calculated as a function of current density i, MEA surface S, Faraday constant F, thanks to Faraday's Law in Equation [3]. ΔH<sub>LHV</sub> is the Low Heating Value (242 kJ mol⁻¹), Δt<sub>nominal</sub> and Δt<sub>recovery</sub> are respectively the duration during nominal operation and during recovery phases.

$$ F_{H2} = \frac{i S}{2 \cdot F} \quad (3) $$

At short-stack level, the same assumption are considered at the exception of recovery current. While recovery current is artificially set to 1 A cm⁻² to remain realistic with PEMFC system operating conditions at differential cell level, real current during the recovery phase is taken into account for the calculation of hydrogen efficiency in Short-stack experiments. Nevertheless, power output during recovery is still considered equal to 0. Moreover, H₂ system stoichiometry is still considered equal to 1.01 similarly to what is done at differential cell scale.

### 2.4.3. Testing precautions during the application of recovery cycles on differential cells

For sake of comparison between different tests, we limited cell operation at maximum 50 h in order to mitigate huge performance gap between the beginning and the end of each test campaign. Therefore, no prediction on performance evolution over more than 50 h can be made with this specific set-up. To further mitigate previous short-term degradation, the sensitivity of each parameter is always compared to a reference recovery cycle performed on every cell, which consists in 1 s at 0.1 V every 10 min at 0.8 A cm⁻² as nominal current density. The impact of recovery parameters is then always compared to this reference recovery cycle.

Moreover, maximum duration of daily trial for each cell is limited to 12 h of operation. Consequently, only 3 different sets of recovery parameters are tested per day by applying 10 to 15 recovery cycles with each set of parameters. Identical test procedures are strictly applied to all cells including break-in procedures, daily conditioning prior to 100 min standard galvanostatic operating phase at 0.8 A cm⁻² before applying our sensitivity study. Only 4th to 9th first complete cycles are taken into account when calculating hydrogen efficiency of operating cycle. Polarization curves by cyclic voltammetry from OCV to 0.1 V (2 scans at 10 mV s⁻¹) are performed afterwards in order to mitigate effects of previous short-term operating conditions on cell performance for the next set of recovery parameters.

## 3. Experimental results at single cell level

### 3.1. Influence of main recovery parameters

Three recovery parameters are studied:

- The cell voltage value during the recovery phase;

- The duration of the recovery phase at low potential;

- The duration of the nominal phase, between two recovery phases.

An experimental sensitivity analysis is conducted for these three parameters. Each test result is compared to the reference recovery that is set at 1 s recovery duration at 0.1 V every 10 min. This reference recovery enables an average nominal cell voltage gain around 10 mV compared to standard galvanostatic operation without recovery phases.
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For each test, mean cell voltage at nominal conditions and mean hydrogen efficiency over the recovery cycles are calculated over the 4th to 9th recovery cycles to avoid calculation defaults and to mitigate transient effects. Results are then presented in respectively Fig. 3 a. and Fig. 3 b. Each result is associated to a standard deviation calculated with each cycle of the test.

Fig. 3 a. illustrates the relative gain of average nominal voltage compared to the reference recovery phase (1 s at 0.1 V every 10 min). It reaches approximately 2 mV when applying 5 s and 9 s recovery phases. This suggests that the reduction of oxidized active sites is only partial with a recovery phase of 1 s. The same trend is also observed for shorter recovery durations, 0.2 s and 0.5 s, as a slight decrease of mean cell voltage can be noticed. However, when comparing hydrogen efficiencies on Fig. 3 b., a different trend is visible. Indeed, hydrogen efficiency is significantly lower for recovery durations superior to 1 s despite the voltage benefit, representing a percentage difference of 0.26 and 0.68 for recovery durations of respectively 5 s and 9 s. Yet, for recovery durations under 1 s, hydrogen efficiency seems to stagnate although voltage is slightly lower. These results demonstrate that hydrogen consumption during recovery is not negligible and has a high impact on hydrogen efficiency. This physical parameter is therefore crucial and more representative than raw electrochemical performance during nominal phase to optimize stack/system efficiency. Moreover, an optimum between superior voltage and higher fuel consumption is found between 0.5 and 1 s recovery.

Recovery cell voltage can also influence hydrogen efficiency as cathode potential affects the kinetics of platinum oxide reduction. Three different recovery voltages are applied: 0 V, 0.1 V and 0.2 V for 1 s every 10 min 0.1 V and 0.2 V show similar mean voltage, but 0 V recovery voltage slightly increases mean nominal voltage compared to the reference at 0.1 V recovery voltage. This suggests that lower recovery voltage enables a better recovery for 1 s recovery duration. Trend for hydrogen efficiency is similar as hydrogen consumption is not influenced by recovery voltage at differential cell level.

The duration of the nominal phase can also be optimized to mitigate hydrogen consumption during the operating cycle. Indeed, it is possible to extend the duration between every recovery phases to reduce overall hydrogen waste caused by the recovery phase but at the expense of a decrease of the average nominal voltage. Therefore, a compromise must be found between the reduction of the cell voltage over time and the extra hydrogen consumption during recovery. Determining experimentally the optimum duration between recovery phases is however complicated due to the number of tests required. Consequently, we have averaged the cell voltage during 10 nominal phases of the reference

cycle (Fig. 4a). Then a logarithmic function [4] with adjusted coefficients a, b, c was defined to fit experimental data. It is assumed that the electrochemical performance of the cell remains reproducible and identical after recovery phases whatever the duration at nominal operation. Based on this fitting curve, it is possible to estimate the efficiency of operating cycles with 1 s recovery phase at 0.1 V for different nominal durations from 60 s to 600 s with 20 s steps (Fig. 4b).

$$f(x) = a \log(b+x) + c \quad (4)$$

When simulating the corresponding hydrogen efficiency, an optimum of 3 min 20 s duration at nominal conditions appears. Compared to the hydrogen efficiency in standard galvanostatic operation without any recovery phases, this optimum allows a theoretical benefit of 0.8 %pt. In standard galvanostatic operation without recovery phases, such benefit in hydrogen efficiency is equivalent to a mean voltage gain of 14 mV at 0.8 A cm⁻² (Fig. 4b). Moreover, this optimum duration allows an increase of 5.6 mV compared to the reference recovery cycle (Fig. 3b). To confirm both this preliminary simulation and the expected efficiency gain, operating cycles with recovery phases every 3 min 20 s have been carried out. Experimental results (Fig. 3) is in agreement with the value predicted by our model, thus validating this approach. Such methodology can be further used at stack level to optimize the duration of nominal phase for a given recovery protocol (recovery cell voltage and duration of the recovery phase).

To conclude, in differential cell configuration, hydrogen efficiency of recovery cycles can be increased by three means. First by lowering recovery voltage as much as possible (~0 V), which is a practical advantage in a PEMFC system. Indeed, reaching ca. 0 V at stack terminals can be more easily achieved by short-circuit or by reducing air stoichiometry below 1 considering constant current set point. On the other hand, higher cell values such as 0.1 V or 0.2 V would imply unstable operating conditions within the mass-transport limited region. Secondly, recovery durations have to be shortened to 1 s or less. Yet, to take into account PEMFC system constraints and specifically the inertia of pumps and valves used in such systems, we decided to impose a minimum of 1 s recovery duration for future tests. At last, duration between recovery phases can be optimized by simulating typical cell voltage evolution. Such method avoids huge test campaigns to find the best compromise.

## 3.2. Impact of recovery phase during extended operation

We have just seen that recovery procedures can increase the hydrogen efficiency. This benefit may however be mitigated over time by extra degradations caused by operating at low voltage. The objective

<figure><img src="image_4.png" /><figcaption>Fig. 3. Gain for different recovery parameters compared to the reference recovery parameters considering (a) the mean nominal voltage and (b) the hydrogen efficiency. Values are calculated over 4th to 9th cycles for each tests.</figcaption></figure>
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<figure><img src="image_5.png" /><figcaption>Fig. 4. a. Experimental averaged cell voltage after 10 recovery phases of 1 s at 0.1 V and corresponding mathematical fitting during nominal operation. b. Simulation of hydrogen efficiency with different durations of the nominal phase.</figcaption></figure>

of this trial is therefore to quantify the medium-term (few tens of hours) impact of periodic recovery phase. Hence, we applied:

- A period with standard galvanostatic operation at 0.8 A cm⁻² during 24 h without recovery phases

- A period with recovery cycles. Each recovery cycle has 10 min phases in nominal conditions (0.8 A cm⁻²) followed by a potentiostatic phase at 0.1 V to recover performance. In this period, a series of 7 recovery cycles with a recovery duration of 1 s alternate with a series of 7 recovery cycles with a recovery duration of 5 s.

Fig. 5 shows an immediate increase of cell voltage between 20 and 30 mV when applying periodic recovery phases compared to the standard case without recovery phase, a value that is similar to the voltage gain measured by Decoopman et al. [11]. Particularly, 5 s recovery cycles demonstrate slightly better mean nominal voltage than 1 s recovery cycles. However, when extra fuel consumption is taken into account during the recovery phase using the Equation [2], hydrogen efficiency is significantly lower with the series of 5 s recovery at 0.1 V than with the series of 1 s recovery at 0.1 V (Table 2). Indeed, hydrogen efficiency increases by ca. 1.6 %pt with the second series of 1 s recovery compared to the end of the standard operation period. Even after 30 h, an

<figure><img src="image_6.png" /><figcaption>Fig. 5. Evolution of differential cell voltage during extended operation with recovery phases (see Table 1 for detailed operating conditions).</figcaption></figure>
<table><caption>**Table 2**
Evolution of hydrogen efficiency and degradation rate for each periods during test shown in Fig. 5.</caption><thead><tr><th>Hydrogen efficiency</th><th>Beginning of phase</th><th>End of phase</th><th>Degradation rate (µV h<sup>-1</sup>)</th></tr></thead><tbody><tr><td>Without recovery</td><td>54.1 %</td><td>51.9 %</td><td>334 (grey line)</td></tr><tr><td>1 s recovery</td><td>53.5 %</td><td>53.0 %</td><td>134 (magenta line)</td></tr><tr><td>5 s recovery</td><td>53.2 %</td><td>52.7 %</td><td>173 (blue line)</td></tr></tbody></table>

improvement can still be observed, although it is mitigated. This evolution suggests either that:

- Recovery effectiveness reduces over time, assuming that no additional irreversible degradation occurs during operation;

- Effectiveness of recovery phases is constant, assuming that loss of performance is caused by other sources of degradations;

- Both effectiveness of recovery decreases over time and additional degradations occur.

In order to settle between the three hypotheses, we calculated

<figure><img src="image_7.png" /><figcaption>**Fig. 6.** Operating parameters of stack A during 5 s recovery phase by direct starvation and air dilution: cell voltage (a), current density (b), cathodic flowrate (c), cathodic pressure (d), anodic pressure (e), and stack outlet temperature (f).</figcaption></figure>
different degradation rates with and without recovery. Regarding the operating phase without recovery, only the 12 last hours were taken into account (see Fig. 5 Grey line) corresponding to a degradation rate of 334 µV h⁻¹. When applying respectively 1 s (see Fig. 5 magenta line) and 5 s (see Fig. 5 blue line) recovery phases, this degradation is reduced by half (Table 2). During the operating phase with periodic recovery, the cell performance level remains close to the initial value and the hydrogen efficiency is also improved. We can thus conclude that applying periodic recovery procedures does not have a negative impact on cell degradation rate during this test. Nevertheless, the duration of this test is too low to enable a clear conclusion on the effect of recovery procedures on long-term performances.

# 4. Experimental results at short-stack level

Most impactful parameters of recovery are studied here at differential cell level. Yet these results must also be validated at short-stack level in practical use where local operating conditions vary along the cell. There are two main procedures to reach a low cathode potential in a PEMFC stack during operation to perform recovery phases:

- Direct air starvation with an air stoichiometry under 1. In this study, air stoichiometry is periodically set to 0.8 by decreasing air flowrate while keeping current set point constant (to mitigate cathode pressure variations). This reduced stoichiometry leads the cell voltage to drop at approximately 0.05 V;

- Air dilution with N₂ to reduce O₂ molar fraction (keeping constant current set point). Practical limits of nitrogen flowrate capacity impose a reduction of air stoichiometry down to 1.3 in order to obtain an oxygen molar fraction of 6% at stack inlet during recovery phase.

## 4.1. Impact of recovery procedures on stack operating conditions at short-stack scale

Fig. 6 presents the evolution of stack A operating parameters when applying both protocols for 5 s recovery. As expected, direct air starvation leads to an immediate drop of stack voltage (Fig. 6 a.). On the contrary, the cell voltage shortly increases when applying air dilution, due to both the increase of cathode pressure and expelling of remaining air in the air circuit. Nevertheless, reduction of both air stoichiometry and O₂ molar fraction then quickly leads the stack voltage to drop. In both cases, the cell voltage increases after recovery by approximately 40 mV and approximately 20 mV for respectively direct starvation and air dilution. This lesser increase just after air dilution is likely the result of remaining N₂ in the air circuit that mitigates the performance peak of the cells. Then, mean cell voltage evolution remains very similar for both techniques. Recovery procedure also seems to influence stack current density as a peak down to 0.5 A cm⁻² is observed for air dilution at the end of the recovery whereas current density stagnates at approximately 0.6 A cm⁻² for direct starvation (Fig. 6 b.). Recovery procedure also impacts operating parameter with a reduction of cathode pressure due to air consumption and test bench pressure regulation during direct air starvation whereas applying a high nitrogen flowrate during air dilution procedure (Fig. 6 c.) increases cathode pressure to 1.6 bara before being regulated by test bench valves (Fig. 6 d.). Besides, anode pressure is negligibly affected, whatever the recovery procedure, due to its constant flowrate corresponding to vH₂ = 2 at 0.8 A cm⁻² (see Fig. 6 e.). Cell outlet temperature has a slight increase of approximately 1 °C during the recovery (Fig. 6 f.), especially in the direct starvation case where global current is higher and the duration at low potential (0.05 V) is slightly longer. This temperature change remains however slight and well below temperature threshold associated to this type of MEA (90 °C), as coolant flowrate circulating through the cells is high.

## 4.2. Influence of recovery methodology at Short-stack scale on hydrogen efficiency

For both air dilution and direct starvation, it is necessary to confirm results obtained at differential cell scales. If impact of recovery voltage cannot be tested as it would lead to heterogeneities between the cells of the short-stack, it is still possible to confirm effect of different recovery durations. Due to the better stability of operation at short-stack level compared to differential cell, the impact of recovery phase duration is investigated over 6 recovery cycles without any significant impact on cell voltage. It is then compared to performance of stationary operations without recovery. First and last cycles are not considered, in order to avoid calculation defaults and to mitigate transient effects when changing the recovery parameters.

Similarly to differential cell, the impact of recovery duration is studied with both air starvation procedures at short-stack level for 1 s, 5 s and 9 s. Note that these durations are theoretical. In practice, a variation up to an additional second is observed due to test bench inertia (flowmeter regulation time and internal volume of air circuit) between expected and real recovery duration. Of course, calculations of hydrogen efficiency considers experimental recovery duration rather than the theoretical value. Moreover, and contrary to differential cells, hydrogen efficiency is calculated considering real current produced by the short-stack during the recovery phase instead of the default value (1 A cm⁻²) set previously for differential cell (see section 2.4.2).

Fig. 7 a. and Fig. 7 b. shows the evolution of cell voltage over 1 recovery cycle with respectively direct air starvation and air dilution. As noticed previously, voltage peak just after the recovery is mitigated for air dilution compared to direct air starvation. A differential voltage of 10 mV is however obtained for both procedures 10 min after the recovery compared to before the recovery, suggesting that the voltage peak just after recovery negligibly affects cell performance over time.

Impact of both recovery procedures on mean cell voltage in nominal conditions is shown in Fig. 7 c. and Fig. 7 d. For both procedures, nominal voltage is increased by 12 mV compared to standard operation without recovery. This increase occurs regardless of the recovery duration. There is still one exception with the mean voltage for 9 s recovery cycles with air dilution, although this specific result is likely the consequence of an experimental deviation caused by an unexpected stop that occurred just before testing these parameters.

When calculating mean hydrogen efficiency, we can notice that shorter recovery phase increases hydrogen efficiency. Indeed, 1 s recovery enables hydrogen efficiency gain of approximately 0.8 %pt compared to the standard case without recovery, while 9 s recovery has almost no benefit (ca. 0.1 %pt). This result demonstrates that hydrogen consumption is too high to be compensated for 9 s recovery phases, even in the case of 9 s air dilution mentioned previously. It is worth therefore to shorten recovery duration to around 1 s to optimize hydrogen efficiency.

To get further information on current density distribution, a bipolar plate with current density and temperature distribution measurement device (S++®) is inserted in a second 6-cell short stack (stack B). In this case, several operating conditions are different:

- O₂ molar fraction during the application of air dilution recovery phases is set to 7% rather than 6% previously due to test bench capability;

- Air stoichiometry is reduced to 1.1 during air dilution procedure for short-stack B rather than the 1.3 air stoichiometry applied in short-stack A.

- Hydrogen stoichiometry is increased from 1.5 to 2. Nevertheless, no impact of cell performance and recovery effectiveness is expected from this modification.

During direct air starvation at 0.8 A cm⁻² set point with 0.8 as equivalent air stoichiometry, local current density extends between 2 A
<figure><img src="image_8.png" /><figcaption>Fig. 7. Cell voltage on the 2nd recovery cycle of the test (a) with 1 s direct starvation, (b) with 1 s air dilution. (c) Mean nominal voltage gain and (d) hydrogen efficiency gain with standard deviation calculated over 4 cycles with different recovery durations and procedures (see Table 1 for detailed operating conditions).</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>Fig. 8. Effect of two different recovery procedures on Stack B a) current density distribution at the middle duration of the recovery phase b) current density distribution 2 s before and 2 s after recovery phase (see Table 1 for detailed operating conditions).</figcaption></figure>
$cm^{-2}$ and 0.1 A $cm^{-2}$ at respectively air inlet and outlet (Fig. 8 a). This range is higher than under nominal conditions (~0.65–0.85 A $cm^{-2}$). The ratio $\frac{l_{max}}{l_{min}}$ is thus close to 20 during recovery while it is around only 1.4 during nominal operation. On the other hand, air dilution is studied with 7 % O$_2$ molar fraction. This procedure mitigates current heterogeneities during the recovery compared to direct starvation as current density extends only between 1.2 A $cm^{-2}$ and 0.4 A $cm^{-2}$ corresponding to a $\frac{l_{max}}{l_{min}}$ ratio around 3, only twice as high as during nominal working conditions. These different local operating conditions during recovery can be expected to produce different local current densities when getting back to nominal operation.

However, after the recovery (cf. Fig. 8 b.), both procedures increase current heterogeneities in nominal phase. Current density is indeed higher at air inlet than before the recovery phase. Moreover, air dilution procedure does not demonstrate any significant evolution of current heterogeneities under nominal conditions compared to direct starvation procedure (Fig. 8 b.). Moreover, we can notice superior power density in every part of the cell without any specific effect of one recovery procedure. That validates our approach as the entire active area takes advantage of the recovery and suggests that the recovery effect caused by the drop of voltage, namely Pt oxide reduction, is similar for both procedures.

To conclude, both recovery procedures have similar impact on current heterogeneities during nominal operation whereas direct starvation provides more heterogeneities during recovery. Moreover, both procedures yield to similar hydrogen efficiency gain (+0.8 %pt compared to standard operation without recovery) when the same durations are applied for recovery phase and nominal operating phase. Applying air dilution in a PEMFC system would though imply heavier constraints than direct starvation and looks therefore less promising than direct starvation. Indeed, direct starvation depends mainly on the air line specifications and dynamics (compressor or valves), whereas air dilution requires a specific architecture integrating a recirculation loop or equivalent at the cathode. Consequently, direct starvation procedure might seem a better option for the application of recovery phases.

## 5. Conclusions

This study is focused on the mitigation of reversible performance losses caused by Pt catalyst oxidation at the cathode during PEMFC operations by applying periodic recovery phases. Indeed the application of cathode potential drops leads to electrochemical reduction of oxidized platinum active sites. Beyond cell voltage gain during nominal operations, hydrogen efficiency is used in this work to assess the actual benefit of the different recovery protocols and parameters. This indicator takes into account hydrogen consumption during recovery to determine more precisely the net gain at PEMFC system level. Impacts of recovery parameters on hydrogen efficiency are studied at two scales: differential single cell and short stack. At differential cell level, an optimized hydrogen efficiency benefit up to 1.8 %pt has been obtained (corresponding to a gain of more than 20 mV during nominal phase compared to standard galvanostatic operation) by applying cell potential at 0.1 V during 1 s every 10 min. Experiments show that recovery duration should be around 1 s to save hydrogen while improving sufficiently cell performance during nominal operations. A simple simulation approach is also proposed to calculate the most suitable period between two recovery phases to further optimize hydrogen efficiency. At shortstack level, cathode potential drop is obtained by two air starvation procedures: one with diluted air and the second with direct starvation. In both cases, the gain of hydrogen efficiency is around 0.8 %pt under galvanostatic operation. Furthermore, current density distribution is evaluated by measuring local current densities along air circuit during recovery and nominal phases. Both air starvation procedures lead to higher local current heterogeneities than in nominal operation, particularly for direct starvation. Nevertheless, local current density

distribution is similar after recovery phase whatever the applied procedure. Considering system integration in real system, direct starvation solely needs an adequate control of air flowrate and pressure while air dilution would likely require the addition of a recirculation pump at the cathode or at least a connection between air inlet and air outlet in a multi-stack architecture. The integration of the latter would thus be more expensive and would possibly consume more energy. Direct starvation should be then preferred to air dilution since performance gains are similar for both methods. To conclude, applying periodic recovery phases by direct air starvation must be now further studied at stack level to validate these benefits considering long-term operation on both performance and durability aspects.

## CRediT authorship contribution statement

G. Soubeyran: Writing – original draft, Methodology, Investigation, Formal analysis. F. Micoud: Writing – review & editing, Methodology, Investigation, Formal analysis. B. Morin: Writing – review & editing, Supervision, Methodology, Investigation, Formal analysis. M. Reytier: Writing – review & editing, Supervision, Methodology. J. Poirot-Crouvezier: Writing – review & editing, Supervision, Methodology.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Data availability

No data was used for the research described in the article.

## References

[1] P. Pei, H. Chen, Main factors affecting the lifetime of Proton Exchange Membrane fuel cells in vehicle applications: a review, 15, Appl Energy 125 (2014) 60–75.

[2] V.F. Valdés-López, T. Mason, P.R. Shearing, D.J.L. Brett, Carbon monoxide poisoning and mitigation strategies for polymer electrolyte membrane fuel cells – a review, Prog. Energy Combust. Sc. 79 (2020) 100842.

[3] D. Qiu, L. Peng, X. Lai, M. Ni, W. Lehnert, Mechanical failure and mitigation strategies for the membrane in a proton exchange membrane fuel cell, Renew. Sustain. Energy Rev. 113 (2019) 109289.

[4] V. Patil, P.V. Reshmi, S. Prajna, Yashaswini Yashaswi, D. Haleshappa, et al., Degradation mechanisms in PEM fuel cells: a brief review, Mater. Today Proc. (2023). S221478532301670X.

[5] E. Guilminot, A. Corcella, M. Chatenet, F. Maillard, F. Charlot, G. Berthomé, et al., Membrane and active layer degradation upon PEMFC steady-state operation, J. Electrochem. Soc. 154 (11) (2007) B1106.

[6] P. Ren, P. Pei, Y. Li, Z. Wu, D. Chen, S. Huang, Degradation mechanisms of proton exchange membrane fuel cell under typical automotive operating conditions, Prog. Energy Combust. Sci. 80 (2020) 100859 sept.

[7] L. Dubau, L. Castanheira, F. Maillard, M. Chatenet, O. Lottin, G. Maranzana, et al., A review of PEM fuel cell durability: materials degradation, local heterogeneities of aging and possible mitigation strategies, WIREs Energy Environ. 3 (6) (2014) 540–560.

[8] D.G. Sanchez, T. Ruiu, I. Biswas, M. Schulze, S. Helmly, K.A. Friedrich, Local impact of humidification on degradation in polymer electrolyte fuel cells, J. Power Sources 352 (2017) 42–55, 1 juin.

[9] L.C. Pérez, T. Rajala, J. Ihonen, P. Koski, J.M. Sousa, A. Mendes, Development of a methodology to optimize the air bleed in PEMFC systems operating with low quality hydrogen, Int. J. Hydrogen Energy 38 (36) (2013) 16286–16299, 13 déc.

[10] B. Decoopman, R. Vincent, S. Rosini, G. Paganelli, P.X. Thivel, Proton exchange membrane fuel cell reversible performance loss induced by carbon monoxide produced during operation, J. Power Sources 324 (2016) 492–498, août.

[11] B. Decoopman, Compréhension des mécanismes de dégradation des cœurs de pile à combustible PEM en application automobile [Internet] [phdthesis], Université Grenoble Alpes, 2016 [cité 12 mars 2021]. Disponible sur: https://tel.archives-ouvertes.fr/tel-02990129.

[12] P. Gazdzick, J. Mitzel, D. Garcia Sanchez, M. Schulze, K.A. Friedrich, Evaluation of reversible and irreversible degradation rates of polymer electrolyte membrane fuel cells tested in automotive conditions, J. Power Sources 327 (30 sept 2016) 86–95.

[13] Y. Huang, F.T. Wagner, J. Zhang, J. Jorné, On the nature of platinum oxides on carbon-supported catalysts, J. Electrochem. 728 (2014) 112–117.

[14] M. Zago, A. Baricci, A. Bisello, T. Jahnke, H. Yu, R. Maric, et al., Experimental analysis of recoverable performance loss induced by platinum oxide formation at
the polymer electrolyte membrane fuel cell cathode, J. Power Sources 455 (2020) 227990 avr.

[15] M. Dou, M. Hou, D. Liang, Q. Shen, H. Zhang, W. Lu, et al., Behaviors of proton exchange membrane fuel cells under oxidant starvation, J. Power Sources 196 (5) (2011) 2759-2762, mars.

[16] E. Colombo, A. Baricci, D. Mora, L. Guetaz, A. Casalegno, An innovative accelerated stress test representative of automotive PEMFC degradation mechanisms validated on 1000 hours real-world operation, J. Power Sources 580 (oct 2023) 233376.

[17] Q. Zhang, M. Schulze, P. Gazdzicki, K.A. Friedrich, Comparison of different performance recovery procedures for polymer electrolyte membrane fuel cells, Appl. Energy 302 (2021) 117490 nov.

[18] T. Chu, Q. Wang, M. Xie, B. Wang, D. Yang, B. Li, et al., Investigation of the reversible performance degradation mechanism of the PEMFC stack during long-term durability test, Energy 258 (2022) 124747.

[19] E. Colombo, A. Baricci, A. Bisello, L. Guetaz, A. Casalegno, PEMFC performance decay during real-world automotive operation: evincing degradation mechanisms and heterogeneity of ageing, J. Power Sour. 553 (2023) 232246.

[20] A.A. Topalov, I. Katsounaros, M. Ainger, S. Cherevko, J.C. Meier, S.O. Klemm, et al., Dissolution of platinum: limits for the deployment of electrochemical energy conversion? Angew. Chem. Int. Ed. 51 (50) (2012) 12613-12615.

[21] A. Bisello, E. Colombo, A. Baricci, C. Rabissi, L. Guetaz, P. Gazdzicki, et al., Mitigated start-up of PEMFC in real automotive conditions: local experimental investigation and development of a new accelerated stress test protocol, J. Electrochem. Soc. 168 (5) (2021) 054501.

[22] Y. Shao-Horn, W.C. Sheng, S. Chen, P.J. Ferreira, E.F. Holby, D. Morgan, Instability of supported platinum nanoparticles in low-temperature fuel cells, Top Catal 46 (3-4) (2007) 285-305.

[23] T. Sugawara, N. Kawashima, T.N. Murakami, Kinetic study of Nafion degradation by Fenton reaction, J. Power Sources 196 (5) (2011) 2615-2620, 1 mars.

[24] N. Zamel, X. Li, Effect of contaminants on polymer electrolyte membrane fuel cells, Prog. Energy Combust. Sci. 37 (3) (2011) 292-329, 1 juin.

[25] S. Maass, F. Finsterwalder, G. Frank, R. Hartmann, C. Merten, Carbon support oxidation in PEM fuel cell cathodes, J. Power Sources 176 (2) (2008) 444-451, 1 févr.

[26] M. Gerard, Étude des interactions pile/système en vue de l'optimisation d'un générateur pile à combustible : -interactions coeur de pile/compresseur- -interactions coeur de pile/convertisseur-, Université de Franche-Comté, 2010.

[27] F. Micoud, A. Morin, J.P. Poirot-Crouvezier, F. Vandenberghe, PROCÉDÉ D'ACTIVATION D'UNE PILE À COMBUSTIBLE, 2023, p. 17. Paris; EP 4113676 A1.

[28] T. Drugeot, F. Micoud, E. Pinton, S. Rosini, J.P. Poirot-Crouvezier, L. Poupin, et al., Experimental assessment of proton exchange membrane fuel cell performance degradations during emulated start-up/shut-down phases, Int. J. Hydrog. Energy 48 (14) (2023) 5630-5642.

[29] T. Drugeot, Compréhension des mécanismes de dégradations et quantification des pertes de performances dans une Pile à Combustible à Membrane Echangeuse de Protons lors des phases d'arrêt/démarrage, Université Grenoble Alpes, 2023 [Grenoble].

[30] Z. Liu, J. Chen, H. Liu, C. Yan, Y. Hou, Q. He, et al., Anode purge management for hydrogen utilization and stack durability improvement of PEM fuel cell systems, Appl. Energy 275 (2020) 115110.