Data from Experimental Analysis of the Performance and Load Cycling of a Polymer Electrolyte Membrane Fuel Cell

: Fuel cells are electrochemical devices that convert the chemical energy stored in fuels (hydrogen for polymer electrolyte membrane (PEM) fuel cells) directly into electricity with high e ﬃ ciency. Fuel cells are already commercially used in di ﬀ erent applications, and signiﬁcant research e ﬀ orts are being carried out to further improve their performance and durability and to reduce costs. Experimental testing of fuel cells is a fundamental research activity used to assess all the issues indicated above. The current work presents original data corresponding to the experimental analysis of the performance of a 50 cm 2 PEM fuel cell, including experimental results from a load cycling dedicated test. The experimental data were acquired using a dedicated test bench following the harmonized testing protocols deﬁned by the Joint Research Centre (JRC) of the European Commission for automotive applications. With the presented dataset, we aim to provide a transparent collection of experimental data from PEM fuel cell testing that can contribute to enhanced reusability for further research.


Summary
The presented dataset contains original raw data files corresponding to experiments carried out with a 50 cm 2 polymer electrolyte membrane (PEM) fuel cell, as reported in Ramírez-Cruzado et al. [1]. A detailed description of the test bench and the fuel cell components is provided in [1]. A 50 cm 2 single cell from ElectroChem Inc. (Woburn, MA, United States) was used in the experiments. Graphite bipolar plates were used, with a serpentine flow field in a cross-flow layout [1]. The membrane was a Nafion 112 (DuPont, Wilmington, Delaware, United States) with 1.0 mg Pt/cm 2 catalyst layers. Toray TGP-H-060 gas diffusion layers (GDLs) by Toray Industries, Inc., Tokyo, Japan, were used in the cell, without microporous layers (MPL). The experimental testing was carried out according to the testing protocols defined by the Joint Research Centre (JRC) of the European Commission for automotive applications [2].
The dataset relates to two main kinds of experiments: • Firstly, cell performance experiments, where the polarization curves were recorded for different operating conditions. All testing conditions were variations with respect to reference conditions representative of automotive applications. By doing this, the impact of different variations in the temperature of the cell, pressure of reactants, or cathode stoichiometry could be analyzed. The operating conditions tested are indicated in Table 1 [1]. For the cell performance experiments, most of the operating conditions were repeated three times in order to enable reproducibility of the experiments, as described in [1]. • Second, durability experiments, where an example of the application of load changes according to the New European Driving Cycle (once adapted to fuel cells as indicated in [2]) is provided. This data set contains data of the polarization curve at the beginning of the test and at the end of the test in order to assess the eventual cell degradation, which was discussed in Ramírez-Cruzado et al. [1]. The dataset was obtained during cell testing research work corresponding to the development of the funded research projects referenced at the end of this paper: The main publication based on the dataset is Ramírez-Cruzado et al. [1]. The lack of availability of real experimental data is hindering the research and development of PEM fuel cell technology. With the presented dataset, we aim to provide a transparent collection of experimental data on PEM fuel cell testing that can contribute to enhancing reusability for further research.

Data Description
The data contained in this work (as Supplementary Materials) are the following. A compressed .rar file is provided (Experimental_performance_load_cycling_PEMFC.rar), wherein two folders are included: • Cell_Performance_Data. This folder contains four subfolders, corresponding to the different groups of tests indicated in Table 1 Cathode_stoichiometry_tests contains Lambda_cat_3_5.rar (corresponding to λ c = 3.5), Lambda_cat_2_0.rar (corresponding to λ c = 2.0), and Lambda_cat_1_3.rar (corresponding to λ c = 1.3).

•
Cell_Load_Cycling_NEDC_Data. This folder contains an ASCII (text) file with the experimental raw data of the test, named Cell_Load_Cycling_NEDC_experiment.rar. After decompression, the original raw data file can be obtained.
All raw data files are organized with the same structure. There is one raw datum for each clock time, where the acquisition time was 1 s. All variables recorded during the experiment are presented in columns. Table 2 indicates the original name of the column (in Spanish language), the translated name of the column, the units of the variable, and a brief explanation. The locations of the different instrumentation are shown in Figure 1, where a simplified P&ID (Piping and Instrumentation Diagram) is included for the sake of clarity.  Figure 1; 2 not used in the experiment; 3 not calibrated, not used in the experiment (Relative Humidity in reactant supply is set by adjusting humidifier temperature and line temperature). Table 2.

Methods
The data were acquired with an acquisition time of 1 s and a dwell time of 200 s. The experiments were carried out according to the testing protocols described in [2], where the last 30 datasets for each current density were used for the derivation of the polarization curve (acquisition time). Most polarization curves were repeated three times in order to assess the reproducibility of the measurements. This was depicted in [2] by including error bars in the measurement points (calculated using the standard deviation of the three samples).

User Notes
The first part of the datafiles corresponds to the start-up of the cell in order to reach the current density defined for the conditioning step described in [2], which corresponds to 0.5 A/cm 2 . The last column corresponds to the current, which can be easily converted to current density by dividing by the active area of the cell (50 cm 2 ). In order to have a quick overview of the data and the overall test contained in each datafile, it is recommended to create a graph representing cell voltage and cell intensity against time. The polarization curves consist of both the increasing current step and the decreasing current step, as described in [1,2].