Influence of contaminants on PEMFC performance – a multisinglecell approach

The impact of materials used in balance of plant (BoP) components of the proton exchange membrane fuel cell (PEMFC) is studied and the effect of the released contaminants on the performance of platinum (Pt) cathode catalyst are evaluated using multisinglecell (MSC) approach as an in-situ electrochemical tool. The effect of contaminants released from ethylene-propylene diene monomer (EPDM) and fluoroelastomers-based (FKM) materials is studied by measuring PEMFC voltage drop as a function of time at different temperatures. Sulfur cross-linked EPDM and FKM give a drastic poisoning effect with irreversible voltage loss of ∼25 mV and ∼35 mV respectively, without any pre-heat treatment. The pre-heat treatment of these materials significantly reduces the influence of contaminants on the Pt catalyst. Mass spectrometry (MS) analysis further reveals the extent of sulfur-based contaminants (CS2) from sulfur-cross-linked EPDM at temperatures 50 °C – 200 °C. The low concentrations of CS2 within the operating temperature (<100 °C) of PEMFC can have a strong contamination effect on the Pt catalyst and its recoverability. The results showed that peroxide-cross-linked EPDM is a very promising candidate to replace FKM, which can release perfluoroalkyl substances (PFAS)

Modified catalyst layer interfaces for higher utilization and improved operational flexibility of low loading polymer electrolyte fuel cell catalyst layers

Featuring low operational temperature and high-power density, polymer electrolyte membrane fuel cells (PEMFCs) have become the most researched and used fuel cell for the emerging automotive applications. To further promote the competitiveness of the fuel cell, improvement in operational flexibility to enable fuel cell to maintain its performance under various conditions is critical. The approach taken here was to modify the membrane electrode assembly (MEA) structure, particularly the interfaces of the cathode catalyst layer. Two interfaces were studied and modified, namely the membrane | cathode catalyst layer (CCL) and the CCL | microporous layer (MPL) interfaces. Firstly, the interface of the membrane and CCL was modified by addition of a thin, dense Pt layer in the membrane subsurface (<250 nm). This Pt layer was physically and electrochemically characterized. The application of this platinized membrane with a loading <20 µgPt/cm⁻² demonstrates a comparable performance to the baseline but improves the performance at low humidity conditions due to a better humidification of the membrane and catalyst layer. The performance benefits are also maintained during a longer humidity cycling test. This new platinized membrane structure also shows reduction in hydrogen crossover (up to 65%) with the loading studied (<80 µgPt/cm⁻²). Secondly, the interface of the CCL and MPL was modified by applying a modified MPL directly on the CCL. A new MEA architecture with a modified MPL consisting of 0.8 mgVC/cm⁻² reduces gaps at this interface, and hence reduces cell contact resistance by 31% and increases the limiting current density by about 10%. The modified MPL with 0.8 mg/cm⁻² Acetylene Black shows the highest performing MEA with ~37% maximum power density gain, while the optimum loading for VC-based MPL is ~0.4 - 0.8 mg/cm² yielding ~27% maximum power density gain at 100% RH. The loading of 0.8 mg/cm⁻² appears to be the threshold to enable the modified MPL to have performance benefits under low humidity. The long-term performance under low and high humidity showed that MEAs with additional modified MPL have a more stable and lower performance drop than for MEAs with a conventional MPL only.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat

Relationship between Electroless Pt Nanoparticle Growth and Interconnectivity at the Membrane Interface: Implications for Fuel Cell Applications

Growth of Pt nanoparticles by electroless deposition of Pt ions in a cation exchange membrane (Nafion) has been characterized and modeled with respect to the interconnectivity of the nanoparticles. With the nonequilibrium impregnation-reduction method, Pt nanoparticles formed a thin layer (≤200 nm) with metal loadings ranging from 10 to 70 μgPt cm–2. The growth of the Pt nanoparticles is influenced by a combination of grain growth and coalescence and shows a power law dependence on the Pt grain size for the range of Pt loadings examined. The platinized membranes were carefully characterized by a number of analytical techniques to obtain correlations between Pt nanoparticle loading, grain size, and interconnectivity. The variation of electrochemically active surface area (ECSA) and Pt crystallite size with the impregnated Pt content is presented. This low loading, high density platinized membrane can be used as an extended catalyst layer at the membrane interface to improve fuel cell operational flexibility, especially under dry conditions. In addition, simple relationships between the ECSA, Pt utilization, grain dimension, and interconnectivity are shown

The Impact of Subsurface and Thin Pt Layer in Nafion Membrane on H₂/O₂ PEM Fuel Cell Performance

Electroless deposition is a simple and scalable method to deposit a thin layer of Pt in the membrane that has been demonstrated in a number of studies [1]–[6]. Recent advancements in the deposition method has enabled deposition of an ultra-thin Pt layer in Nafion (&lt; 200 nm) [5], but no thorough study with respect to the impact of deposition parameters on the physical structures and fuel cell performance has been reported in the literature. For fuel cell applications, it is essential to design an optimum platinized membrane structure which maximizes Pt utilization while minimizing the Pt loading. In this study, the ultra-thin electroless deposited layers with various loadings were studied and characterized physically and electrochemically. Grain size and ECSA characterization from XRD and CV analysis indicate that inter-particle electrical connectivity was improved as the Pt loading increased, until the loading reached a value of about 52 μgPt/cm2 (Figure 1). Fuel cell polarizations and constant current operation under different humidity levels were examined with the additional electroless deposited Pt layers at loadings below 45 μgPt/cm2 than for the standard MEAs. The kinetic performance of the electroless deposited Pt layers in the membrane was also examined and will be presented at the meeting. Figure 1 <jats:p /

Reduction of Interfacial Gaps and Enhancement of PEM Fuel Cell Performance Via a New CCL|MPL Architecture

A new enhanced architecture for fuel cell membrane electrode assemblies (MEAs) which incorporates deposition of an MPL layer directly on a catalyst coated membrane (CCM) is demonstrated. This modified MPL helps to reduce interfacial gaps present between the catalyst layer and the conventional MPL-coated gas diffusion layer of the MEAs and reduces water accumulation, which ultimately results in higher power densities (Figure 1). Three types of commercial carbon black with different porosity and hydrophilicity were directly deposited on the low loading cathode catalyst layers (0.1 mgPt cm−2) of membrane electrode assemblies (MEAs) used in H2/O2 fuel cells. Among the carbon materials investigated, Acetylene Black- and Vulcan XC72R-based modified MPLs (mass loadings ~ 0 – 1.0 mg cm−2) lead to higher performance in the high current density regions due to their lower porosity and higher hydrophobicity. Detailed information about this approach, preparation and performance characteristics will be discussed during the meeting. Figure 1 <jats:p /

Prompts to improve post-consumer waste composting behaviors in the SUB

The Alma Mater Society (AMS) of the University of British Columbia (UBC) is striving to be leaders in campus sustainability by providing resources for student-run sustainability projects and creating in-house initiatives. A current focus is providing new sustainability features, such as on-site composting for new rooftop gardens, in the new Student Union Building (SUB). However, a significant barrier to this project is the level of contamination, in the form of non-compostable waste and materials, within the post-consumer organics bins in the SUB. The goal of this project is to increase the weight (wt) of compostable waste collected in the compost receptacle opposite ‘Pie R Squared’ in whilst simultaneously reducing the % wt contamination. This was achieved by designing visual behavioural prompts in the form of a large poster and small table toppers. Thorough analysis of literature research on visual prompts led to a design focused on clarity of information, proximity to composting receptacle and positive tone. The contamination after installation of the prompts was compared against baseline data and it has been concluded that both the % wt. contamination and % contamination level were decreased post-intervention. However, the weight of compostable has decreased post-intervention as well. Other compounding factors should be considered when assessing the data, including the sustainability fair occurring during baseline data collection and improvement of old bins with more user-friendly containers post-intervention. Suggestions for further efforts to improve the quality of compost involve the construction and installation of an audio prompt system based on infrared sensor technology. The infrared sensor would measure the humidity of the waste as a reflection of the content of compostable food waste in the bin. An audio message would play, thanking students who compost their organic material, as positive reinforcement for their good behaviour. Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report.”Applied Science, Faculty ofChemical and Biological Engineering, Department ofUnreviewedGraduat

Engineering and Testing of CCM Modifications for Improved Operational Flexibility, Durability and Performance of Fuel Cells and Electrolyzers

The performance, durability and cost of PEM fuel cell and electrolyzer systems still requires further improvements before they can be widely adopted. Along with improved electrocatalysts, low cost interface modifications and intermediate layers are important to improve the operation of catalyst coated membranes (CCMs) and meet commercial requirements. In this presentation we present some examples of the modification of conventional commercial CCM and MEA modifications with performance benefits. This would include for example the effect of improving the microporous layer (MPL) / catalyst layer (CL) interface by reducing the gaps to improve power density1, the improvement of cross-over and operational flexibility with a thin electrolessly deposited catalyst layer at the membrane surface 2, and modification of the porous transport layer (PTL) / catalyst interface3. A new testing method for the evaluation of commercial CCMs was used in this work which can accelerate design and testing of these new and modified CCMs. This new method uses a Modified Rotating Disk Electrode (MRDE)4 which allows electrodes and CCMs to be tested up to high current densities, e.g., 2 A/cm2, and eliminates the variability and issues associated with thin film RDE testing. Figure 1 shows an example of testing the oxygen evolution reaction (OER) performance for different PTLs with a commercial CCM using the MRDE. The MRDE testing is also useful for carrying out accelerated degradation (ADT) testing of CCMs for fuel cell or electrolyzer applications5 and has the potential to be used as a quality control tool for CCM manufacturing lines. References: L. Daniel, A. Bonakdarpour and D.P. Wilkinson, Fuel Cells, 20(2), F1-F7 (2020) L.Daniel, A. Bonakdarpour and D.P. Wilkinson, ACS Applied Nano Materials, 2, 3127-3137 (2019); J. of Power Sources, 471, 228418 (2020) M. Kroschel, A. Bonakdarpour, J.T.H. Kwan, P. Strasser and D.P. Wilkinson, Electrochim. Acta, 317, 722-736 (2019) J. T. H. Kwan, A. Bonakdarpour, G. Afonso, and D. P. Wilkinson, Electrochim. Acta, 258, 208–219 (2017). P.J. Petzold, J.T.H. Kwan, A. Bonakdarpour, and D.P. Wilkinson, J. Electrochem. Soc., 168(2), 026507 (2021) Figure 1: The effect of different titanium current collector meshes on OER performance using a commercial IrO2-based CCM obtained by the MRDE tool. Inset shows the pictures of different Ti meshes examined. Figure 1 <jats:p /