EU harmonised terminology for low temperature water electrolysis for energy storage applications

This report was prepared under the Framework Contract between the Joint Research Centre (JRC) and the Fuel Cells and Hydrogen second Joint Undertaking (FCH2JU). This document is the result of a collaborative effort between industry partners, research organisations and academia participating in several Fuel Cell and Hydrogen second Joint Undertaking funded projects in Low Temperature Water Electrolysis applications. The objectives of the report is to present to those involved in research and development a comprehensive and harmonised compendium of various terminology terms which are encountered in low temperature water electrolysis applications.JRC.C.1-Energy Storag

EU HARMONISED TEST PROTOCOLS FOR PEMFC MEA TESTING IN SINGLE CELL CONFIGURATION FOR AUTOMOTIVE APPLICATIONS

PEMFC due to their high energy density, low operating temperature and high efficiency are considered to be very suitable for vehicle propulsion. In such applications, fuel cells could encounter operating conditions which are severe to the materials involved. Fuel cell testing shall as close as possible reflect conditions encountered in real life. To enable a fair comparative assessment of the performance of MEA under operating conditions foreseen in future automotive applications, a set of representative operating conditions in addition with a test methodology is proposed. The aim of a unified set of harmonised operating conditions is to comparatively test and evaluate the performance of different MEAs in single cells. The current document is the result of a cumulative effort of industry and research organisations participating in FCH-JU funded projects for automotive applications, in establishing a harmonised test protocol for assessing PEMFC performance and durability at a single cell level. This document presents a set of reference operating conditions such as temperature, pressure, humidification, gas flow and composition at the fuel and oxidant inlet representative for future automotive applications. It also defines boundaries of these conditions within which the cell is expected to operate. While not specifying single cell design details, cell operation in counter flow is mandatory for comparative assessment. A methodology is established to examining the relative influence that the individual operating parameters exert on the MEA performance in single cell configuration once the cell is subjected to the more challenging boundary conditions defined in this document which are also called as stressor conditions. In addition to operating conditions, the most likely stressor conditions for single cell testing could be identified as follows: Load cycling, Mechanical effects, Fuel Air contaminants (impurities), and Environmental Conditions. In this document the focus is on stressors related to Operating Conditions and Load Cycling. Deviations from the automotive reference Operating Conditions may result in changes to both cell performance and durability. In principle the influence of each stressor on cell performance could be studied individually. However, since a number of stressors are inter-linked, (changing the value of one stressor could inevitably change the value of another), the stressor tests have been grouped into four families of Stressors, namely: Cell Temperature Stressor Tests, Reactants Gas Inlet Humidification Stressor Tests, Reactants Gas Inlet Pressure Stressor Tests, Oxidant Stoichiometry Stressor Tests. The aim of these tests is to study the effect of each stressor on the the cell voltage at three different current densities representative of activation, ohmic polarization and mass transfer regimes as a function of each stressor condition. The successful operation of a fuel cell depends not only on its performance but also on its durability. Fuel cell durability is evaluated through endurance testing by applying a repetitive load profile to the cell and measuring performance degradation in terms of cell voltage decrease as function of operating hours. To assess the cell degradation rate a dynamic load cycle for endurance testing is proposed. The Fuel Cell Dynamic Load Cycle is used in this document and is derived from the New European Driving Cycle modified for fuel cell applications. In addition to the definition of representative reference and stressor operating conditions, the document also provides a rationale for their selection. The use of sound science-based, industry-endorsed test methodologies and protocols enables true comparison of MEAs originating from different sources either commercial or developed within different projects. It also enables evaluating the rate of progress achieved towards reaching agreed technology performance targets.JRC.F.2-Energy Conversion and Storage Technologie

CO Desorption Kinetics at Concentrations and Temperatures Relevant to PEM Fuel Cells Operating with Reformate Gas and PtRu/C Anodes

The kinetics of the CO desorption process have been determined using isotopic exchange experiments at concentrations and temperatures relevant to PEM fuel cells operating with reformate gas and commercial carbon supported platinum-ruthenium alloy anodes. The CO desorption kinetics have been studied as a function of CO concentration, temperature and flow rate. Desorption rate constants have been determined experimentally for a wide range of concentrations (100-500ppm) and temperatures (25-150°C) and have been extrapolated to one order of magnitude lower CO concentration range between 10 and 100ppm, which is directly relevant to PEM fuel cells operating with reformate gas. The desorption rates measured for the 100-500ppm CO concentration range appear to be significantly larger than previously published CO oxidation data, suggesting that the CO desorption process plays a more significant role in determining the equilibrium CO coverage at the fuel cell anode than the electrochemical CO oxidation process. The proposed desorption rate values at the lower 10-100ppm CO concentration range and at relevant temperatures are believed to be of added value for the modelling of PEM fuel cells operating with reformate gas and PtRu/C anodes, since significantly different empirical values have been used up to now for the modelling of the CO desorption process. The variation of the apparent Arrhenius parameters as a function of CO concentration provides also some insight into the CO poisoning effect and the underlying adsorption/desorption processes.JRC.DG.F.2-Cleaner energ

CO Desorption Kinetics under Conditions of Relevance to PEM Fuel Cells Operating with Reformate Gas

The kinetics of the CO desorption process have been investigated on a PtRu/C anode using isotopic exchange experiments under conditions of relevance to PEM fuel cells operating with reformate gas. Desorption rate constants have been determined experimentally for a wide range of concentrations (100-1000 ppm) and temperatures (25-150°C) and have been extrapolated to one order of magnitude lower CO concentration range between 10 and 100 ppm, which is directly relevant to PEMFC operating with reformate gas. The results are discussed with relation to the CO tolerance issue at the PEM fuel cell anode and to the development of more accurate models for PEM fuel cells operating with reformate gas.JRC.DDG.F.2-Cleaner energ

The surface coverage of PEM fuel cell electrodes

A quantitative study was conducted about Hydrogen (H2), water (H2O) and carbon monoxide (CO) bond concentration on a Pt-Ru catalyst surface used for PEM fuel cells. Strong hydrogen bonds which can withstand CO exposure at 50 °C were calculated as 54% of the total hydrogen bonds present on catalyst surface during pure H2 purge. The very weak hydrogen bonds that could be removed with pure inert gasses were not taken into account. Additionally, water and hydrogen content on the surface of catalyst layer was compared and hydrogen bond ratios of 33 – 63 % were obtained for different temperatures (25 °C, 50 °C and 75 °C) and relative humidity values (Dew Point Temperatures of 25 °C, 35 °C and 45 °C). Furthermore 10 ppm CO exposure time was varied from 30 second to 1 hour at 50 °C. Majority of the weak hydrogen bonds desorbed in first 10 minutes with 300 sccm gas flow over 9.5 cm2 Pt-Ru catalyst layer. Desorption process stopped after 10 minutes. The hydrogen bonds were strong enough to stick to the surface during 10 ppm CO exposure at 50 °C. Hydrogen bond content ratio of 66-67 % was calculated for 10 – 60 minutes of 10 ppm CO exposure.JRC.F.2-Energy Conversion and Storage Technologie

Investigation of PEM Fuel Cell Electrodes by Transmission Electron Microscopy, Scanning Electron Microscopy and -Ray Diffraction

PEM fuel cell electrodes were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and x-ray diffraction (XRD). As one example of the application of these techniques, catalyst nanoparticles were characterized before and after desorption experiments up to 150°C, in the frame of temperature-dependent CO desorption kinetics experiments, which are of importance for a better understanding of the fundamental physicochemical processes involved in improving CO tolerance. Particle diameter distributions of a novel Pt-on-Au based catalyst nanomaterial were determined from TEM data and compared with average sizes calculated from XRD data.JRC.DDG.F.2-Cleaner energ

Effect of Humidity on Carbon Monoxide Desorption Kinetics

The kinetics of carbon monoxide desorption on a platinum catalyst under humidified conditions were investigated with the steady state isotropic transient kinetic analysis (SSITKA) method. The effect of the humidity level on desorption kinetics was quantified. The carbon monoxide (CO) desorption kinetic constant was calculated regardless of the gas flow rate. The kinetic constant dropped up to 58% with the increasing relative humidity. The negative effect of humidity in terms of CO poisoning for PEM fuel cells was determined.JRC.F.2-Energy Conversion and Storage Technologie

Kinetic Study of CO Desorption from PtRu/C PEM Fuel Cell Anodes - Temperature Dependence and Associated Microstructural Transformations

The temperature dependence of the CO desorption process on a carbon supported platinum-ruthenium alloy catalyst has been investigated using isotopic exchange experiments. The kinetics of CO desorption on PtRu/C catalyst have been studied as a function of temperature and flow rate. Desorption rate constants have been determined for a temperature range between 25°C and 150°C. All PtRu/C results have been compared with those obtained for the Pt/C catalyst under similar experimental conditions. Quite different desorption rate constants have been observed. The variation in apparent Arrhenius parameters (frequency factor A and activation energy Ea) for PtRu/C and Pt/C could possibly explain their different degrees of poisoning by CO in Proton Exchange Membrane Fuel Cells (PEMFC) and the underlying adsorption/desorption processes. The effect of temperature treatment on the PtRu/C catalyst properties has also been investigated with respect to CO desorption kinetics and to the associated microstructural transformations.JRC.F.2-Cleaner energ

Immittance data validation using Fast Fourier Transformation (FFT) computation - synthetic and experimental examples

Exact data of an electric circuit (EC) model of RLC (resistor, inductor, capacitor) elements representing rational immittance of LTI (linear, time invariant) systems are numerically Fourier transformed to demonstrate within error bounds applicability of the Hilbert integral tranform (HT) and Kramers-Kronig (KK) integral tranform (KKT) method. Immittance spectroscopy (IS) data are validated for their HT (KKT) compliance using non-equispaced fast Fourier transformation (NFFT) computations. Failing of HT (KKT) testing may not only stem from non-compliance with causality, stability and linearity which are readily distinguished using anti HT (KKT) relations. It could also indicate violation of uniform boundedness to be overcome either by using singly or multiply subtracted KK transform (SSKK or MSKK) or by seeking KKT of the same set of data at a complementary immit- tance level. Experimental IS data of a fuel cell (FC) are also numerically HT (KKT) validated by NFFT assessing whether LTI principles are met. Figures of merit are suggested to measure success in numerical validation of IS data.JRC.C.1-Energy Storag

Assessment of PEFC Performance by Applying Harmonized Testing Procedure

The performance of Polymer Electrolyte Membrane Fuel Cell (PEFC) stacks is assessed in terms of polarization curve measurements under laboratory conditions by applying a harmonized testing procedure. Harmonization at the level of testing procedures allows for an objective and trustworthy comparison of performance data. The harmonization of the procedure took place among the 55 partners of the Fuel Cell Testing and Standardization Network (FCTESTNET). Selected testing procedures are currently validated through experimental campaigns in the successor project (Fuel Cell Testing, Safety and Quality Assurance, FCTESQA) involving world class research laboratories from Europe, US, China, and Korea. The present study reports the results of a test of the campaign for the performance assessment of a PEFC power stack carried out by JRC applying the harmonized procedure for validation. Following the procedure, the test inputs and outputs are subjected to stability checks a priori to and during the actual polarization curve measurement step of the test. The assessment of the stack performance is based on a statistical approach of the test outputs which includes the calculation of averages, measurement range, (relative) standard deviation and standard error as well as of a stability parameter. The study demonstrates the necessity of harmonized testing procedures and of a harmonized methodology of presenting the test results in a commonly agreed format to provide a comprehensive performance assessment for PEFC stacks.JRC.F.2-Cleaner energ