High-temperature PEM Fuel Cell Characterization: an Experimental Study Focused on Potential Degradation due to the Polarization Curve

High-Temperature Proton Exchange Membrane Fuel Cell constant current ageing tests highlighted that the characterizations used to monitor the state of health of single cells could be potentially degrading. An experimental campaign to analyze potential degradation due to polarization curves was carried out. More exactly, four methodologies to generate a polarization curve including Electrochemical Impedance Spectroscopies (EIS) were cycled 30 times. The tested single cells were based on a commercial PBI Membrane Electrodes Assembly (MEA) with an active surface of 45 cm2 (BASF Celtec®-P 1100 type). Before the first cycling test and after the last cycling one, complete characterizations, composed by a voltammetry and a polarization curve including EIS, were performed. The results show that one of the MEA has a voltage which increased for one of the four methods to obtain the polarization curve. This growth is linked to a decrease of ohmic losses: in an unexpected way, it could be considered as a way to improve the break-in period. Similarly, the monitoring of CO2 emission (as corrosion has been suspected to be involved at high voltage, i.e. low current density) confirms the potential degradation of the electrodes during the measurement of the polarization curve.

Electrode processes during electrodeposition, electropolishing and oxidation of niobium

The electrode processes occurring during the electrodeposition, electropolishing and oxidation of niobium are considered. The discharge of Nb(IV) complexes during Nb electrodeposition was studied by cyclic voltammetry. The anodic polarization curve on niobium in a mixture of acids H2SO4:HF (9:1) was obtained by chronopotentiometry method, the potential range at which the highest quality and speed of electropolishing is achieved was found. The film formation mechanism of niobium pentoxide Nb2O5 on niobium was studied by cyclic voltammetry.

Effect of Magnesium on Corrosion Resistance of Galvalume Coating

In order to improve the performance of Galvalume coating, the expected microstructure and the better property could be obtained by adding 1∼3% Magnesium into Galvalume coating (55%Al-Zn). In this paper, effect of magnesium on the corrosion resistance of 55%Al-Zn coating was studied. The morphology and microstructure of coatings, polarization curve and surface corrosion of two different kinds of samples were analysed by SEM, EDS, electrochemistry workstation and salt spray test. The results show that the numbers of surface spangles by adding 2% magnesium are not changed obviously; the corrosion resistance of 55% Al-Zn-2%Mg coating becomes much better.

Proposal of a New Technique to Obtain Some Fuel Cell Internal Parameters Using Polarization Curve Tests and EIS Results

Nowadays, fuel cells are becoming a real alternative to power several applications, from portable electronic devices to cars, buses, or stationary facilities. Usually, a basic analysis of a fuel cell includes polarization curve test, as this method is excellent to characterize the behavior of a fuel cell as a whole, because it integrates all the different physical process that happens inside in current and voltage signals. On the other hand, it does not provide accurate information of these physical processes as individual. In this research, we relate the results of polarization curve test and EIS (Electrochemical Impedance Spectroscopy) test through two mathematical expressions. Then, using equivalent electrical circuit elements to model EIS curves, and applying the developed expressions, we correlate the EIS and polarization curve results, allowing us to interpret the physical meaning of these circuit elements and obtain a deeper vision of the internal processes that happen.

Poisoning Effect of CO: How It Changes Hydrogen Electrode Reaction and How to Analyze It Using Differential Polarization Curve

The hydrogen electrode reaction (HER) on Pt electrode in a H2SO4 solution when CO gas was injected/stopped was studied using polarization resistance curve [...]

Investigation of Inlet Gas Relative Humidity on Performance Characteristics of PEMFC Operating at Elevated Temperature

Raising the operating temperature is considered to be an effective method to improve the output performance of proton exchange membrane fuel cells (PEMFCs). In this paper, the effects of inlet relative humidity in the anode (RHa) and cathode (RHc) on the polarization curve and impedance spectra of a single rotating serpentine PEMFC were investigated by experimental method at the operating temperature of 90 °C. It was found that the output performance is the smallest in the high RH case (RHa90%/RHc90%) due to the largest mass transfer resistance. However, the ohmic resistance in the dry case (RHa50%/RHc50%) is the highest, and it shows better output performance at more than 1.0 A/cm2 because of the lowest mass transfer resistance. The impact of the changes in the RHa value on the polarization curve is more apparent than that of the RHc changes at high current density. The largest power density can be attained and the efficiency can reach 24.4% when the RHa is 90% and RHc is 50%.

Standardized Procedures Important for Improving Low-Temperature Ceramic Fuel Cell Technology: From Transient to Steady State Assessment

As the stress–strain curve of standardized metal samples provides the basic details about mechanical properties of structural materials, the polarization curve or current–voltage characteristics of fuel cells are vitally important to explore the scientific mechanism of various solid oxide cells aiming at low operational temperatures (below 600 °C), ranging from protonic conductor ceramic cells (PCFC) to emerging Semiconductor ionic fuel cell (SIFC)/Semiconductor membrane fuel cells (SMFC). Thus far, worldwide efforts to achieve higher nominal peak power density (PPD) at a low operational temperature of over 0.1 s/cm ionic conductivity of electrolyte and super catalyst electrode is the key challenge for SIFCs. Thus, we illustrate an alternative approach to the present PPD concept and current–voltage characteristic. Case studies reveal that the holy grail of 1 W/cm2 from journal publications is expected to be reconsidered and normalized, since partial cells may still remain in a transient state (TS) to some extent, which means that they are unable to fulfill the prerequisite of a steady state (SS) characteristic of polarization curve measurement. Depending on the testing parameters, the reported PPD value can arbitrarily exist between higher transient power density (TPD) and lower stable power density (SPD). Herein, a standardized procedure has been proposed by modifying a quasi-steady state (QSS) characterization based on stabilized cell and time-prolonged measurements of common I–V plots. The present study indicates, when compared with steady state value, that QSS power density itself still provides a better approximation for the real performance of fuel cells, and concurrently recalls a novel paradigm transformation from a transient to steady state perspective in the oxide solid fuel cell community.

Resistance Separation of Polymer Electrolyte Membrane Fuel Cell by Polarization Curve and Electrochemical Impedance Spectroscopy

The separation of resistances during their measurement is important because it helps to identify contributors in polymer electrolyte membrane (PEM) fuel cell performance. The major methodologies for separating the resistances are electrochemical impedance spectroscopy (EIS) and polarization curves. In addition, an equivalent circuit was selected for EIS analysis. Although the equivalent circuit of PEM fuel cells has been extensively studied, less attention has been paid to the separation of resistances, including protonic resistance in the cathode catalyst layer (CCL). In this study, polarization curve and EIS analyses were conducted to separate resistances considering the charge transfer resistance, mass transport resistance, high frequency resistance, and protonic resistance in the CCL. A general solution was mathematically derived using the recursion formula. Consequently, resistances were separated and analyzed with respect to variations in relative humidity in the entire current density region. In the case of ohmic resistance, high frequency resistance was almost constant in the main operating load range (0.038–0.050 Ω cm2), while protonic resistance in the CCL exhibited sensitivity (0.025–0.082 Ω cm2) owing to oxygen diffusion and water content.