Automotive Fuel Cell Cooperation (Canada)

Plants play a vital role in maintaining the ecological cycle, and thus, to maintain the plant's proper growth and health, adequate monitoring is required. Hence, the aim of the chapter is to create a smart plant monitoring system using automation and internet of things (IOT) technology. This topic highlights various features such as smart decision making based on soil moisture real-time data. For this purpose, sensors like soil moisture sensor, DHT11 sensor, level sensor, etc. are used. The soil moisture sensor measures the level of moisture (i.e., water content of different plants). The signal will be sent to Arduino board when the moisture level drops below the marginal value, which triggers the pumping of water into the plant by the pump. When the moisture level reaches absolute value, the pump is halted. The other condition for this process is level sensor. Level sensor senses the water level in the tank and sends the information of water level value to Arduino board and Arduino board to cloud. The whole data about the plant monitoring will be sent to the cloud server.

The thicknesses of thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA), and perfluorosulfonic acid (PFSA) were measured by Ultraviolet Spectral Reflectance (UV-SR) and Scanning Transmission X-ray Microscopy (STXM). At high doses, the UV irradiation in air used in the UV-SR method was found to modify the chemical structures of PS and PMMA (but not PFSA), leading to thinning of these polymer films. The chemical changes caused by UV/air radiation damage were characterized by STXM. When UV and X-ray radiation are applied using no-damage conditions, the film thicknesses measured with the two techniques differ by less than 15% for PS and PMMA and less than 5% for PFSA. This is an important result for verifying the quantitation capabilities of STXM. The chemical damage to PS and PMMA is explained by oxygen implantation from air with formation of ozone. The thickness depletion caused by UV/air radiation for PS and PMMA films is exponential with exposure time. Different rates of depletion are linked to surface or bulk driven photo-chemical product erosion. The initial rate of material erosion was found to be constant and non-specific to the studied polymers.

Access of fuel and oxidant gases to the active catalyst sites in dispersive electrodes of polymer electrolyte membrane fuel cells (PEM-FC) is an important characteristic defining the performance of the whole catalyst coated membrane unit (CCM). The electrode porosity – the ratio of empty space to the whole volume of the electrode – is a metric widely used to characterize the ability of a particular electrode to provide gas transport. It is common practice to present electrode porosity as a number averaged over a macroscopic volume of the electrode [1]. In compliment to already established methods, soft X-ray scanning transmission X-ray microscopy (STXM) offers the possibility to visualize the microscopic network of the pore space in the electrode with ~30 nm spatial resolution. Thus, in addition to average porosity, STXM provides porosity distributions in electrodes, with a local value averaged per voxel of ~1003 nm3. Relative to studies of the electrode porosity visualized by the focused ion beam – scanning electron microscopy method (FIB-SEM) [2], STXM provides direct visualization of the pore-space in the electrode without destroying the sample and omitting the 3D reconstruction process. Here we present STXM porosity distribution for 2D projection of the thin cathode lamella. STXM pore space visualization relies on filling the pores with a material that STXM can discriminate spectroscopically relative to the other components (carbon support, ionomer, and metal catalyst-Pt) [3]. In these experiments the cathode catalyst decals are embedded with a custom epoxy (TTE, the product of reacting trimethylolpropane triglycidyl ether and 4,4’-methylenebis(2-methylcyclohexylamine in 1:1 wt ratio, which results in a final chemical formula (C10H10N3)n and density of 1.0 g/cm3). While the TTE epoxy is fluid it wets well the electrode inner interfaces filling most of the available space. 100 nm thick microtomed sections of the cathode embedded in TTE are measured by STXM at the C 1s edge at the Canadian Light Source (Saskatoon) or the Advanced Light Source (Berkeley). The C1s stacks, consisting of images at 50-70 energies over 280-330 eV with 100 nm pixels, are converted to optical density, and then fit using standard, quantitative reference spectra (OD1 scale) of carbon-support (Cs), ionomer (I), TTE and Pt components to construct 2D component maps of each component. The grayscale value at each pixel is the nm thickness of that component. The total volume is the sum of Cs, I, TTE, and Pt values at each pixel. The 2D porosity map is then the ratio of the TTE map to the total-volume map, where each pixel has a unit of part per volume (ppvol). STXM performed using BL 10ID1 at CLS and BL 5.3.2.2 at ALS. Research supported by NSERC. S. Shukla, et.al., 231 ECS 2017, Abst 97034, https://ecs.confex.com/ecs/231/webprogram/Paper97034.htmlM.Sabharwal, et al., Fuel Cell, 16 (2016) No.6, 734–753H. Ade, et al., Polymers, 49 (2008) 643-675 Figure 1

The perfluorosulfonic acid (PFSA) ionomer commonly used in Polymer Electrolyte Membrane Fuel Cells (PEM-FC) consists of a hydrophobic tetrafluoroethylene backbone with side chains terminated with sulfonate groups responsible for proton conduction. Optimizing the spatial distribution of ionomer in the catalyst layer maximizes the catalyst that is accessible to protons and O2, reducing the Pt loading. Thus, the methods of quantifying the distributions of ionomer relative to catalyst are important. PFSA is prone to radiation damage [1], losing fluorine which makes it challenging to analyze quantitatively with electron [2] and x-ray spectro-microscopies [3]. Scanning Transmission X-ray Microscopy (STXM) is known to cause less damage in soft materials than analytical Transmission Electron Microscopy (TEM), with either core level Electron Energy Loss (EELS) [4] or Energy Dispersive X-ray Spectroscopy (EDS). We have applied Scanning TEM – EDS (STEM-EDS) and STXM at room temperature to the same microtomed sample of a PEM-FC catalyst layer. STEM-EDS was performed using an FEI Tecnai Osiris equipped with CHEM-STEM 4 area detectors. STXM was performed using soft X-ray STXMs at the Canadian Light Source (Saskatoon) and the Advanced Light Source (Berkeley). The extent of ionomer damage (F-loss) as a function of absorbed radiation dose in the cathode due to each imaging technique was measured from F Ka maps in STEM-EDS, and by F1s stack maps (OD694 eV - OD684 eV) in STXM. Figure 1 plots the extent of fluorine signal and thus component loss, normalized to the initial amount, for a range of electron and X-ray exposures. Both the electron and X-ray beams damage the ionomer at a similar rate. However, decent quality EDS maps at room temperature (Figure 1C) with sufficient counts for statistical analysis need ~30000 e-/nm2. At that exposure, approximately 70-80% of the original fluorine signal in the ionomer material is lost. On the other hand, high quality ionomer maps using STXM require less than 10 photons/nm2 (Figure 1A), which causes negligible fluorine loss. The ‘multi’ mode of TEM-EDS acquisition does provide significantly less damage at lower exposures (Figure 1B) but by the time adequate image quality is achieved (Figure 1C), the extent of fluorine loss is unacceptably high. Whether the ionomer damage is attributed to only fluorine loss (EDS), or ionomer component loss (STXM), or significant change of ionomer chemistry is still debatable. However, this study indicates that after applying “common” imaging practices for STXM and EDS, the remaining cathode areas are significantly different. STXM performed on BL 10ID1 at CLS and on BL 5.3.2.2 at ALS. Research supported by NSERC and the Catalyst Research for Polymer Electrolyte Fuel Cells (CaRPE-FC) network. S. Yakovlev, et.al., Membranes. 3(2013) 424–439D.A. Cullen, et al., J. Electrochem. Soc. 161 (2014) F1111–F1117D. Susac, et.al. STXM ECS Trans. 41 (2011) 629–635J. Wang, et.al., J. Phys. Chem. B. 113 (2009) 1869–76. Figure 1

Segmentation of FIB-SEM data remains a major challenge to achieving accurate reconstructions. Epoxy embedding is used in this article to eliminate background data from SEM images in order to aid in segmentation and generate 3D reconstructions of conventional high surface area CLs from FIB-SEM images. Two CL samples with the same composition but different hours of operation, namely, beginning of life (BOL), i.e. post conditioning, and end of life (EOL), i.e., post failure, were used. The samples were imaged with and without epoxy embedding to characterize the difference in the structure of the sample due to sample preparation. Further, the use of two CL samples allowed the quantification of the differences in the structure of the CL due to degradation and ensure validity of the sample preparation across multiple CL samples. Image analysis showed that a simple thresholding algorithm, such as Otsu, was sufficient to accurately segment the images for the sample with epoxy embedding due to the lack of background features. Statistical descriptors, such as porosity, two-point correlation function, chord length function, specific interface area and pore size distribution, and effective diffusion coefficient are used to quantify the differences in the reconstructed structures of the CLs with different sample preparation. Results showed that the CL reconstructions of the epoxy embedded samples had a higher porosity, larger pore sizes and lower specific interface area due to the more accurate segmentation and removal of background features.

Proton exchange membrane fuel cells (PEMFCs) are being developed as alternative energy sources for both residential and automotive applications. For this technology to reach its full commercial potential, however, a significant reduction in cost is still required while the performance and durability of PEMFCs being maintained or improved. The key in this process is continuous improvement of membrane electrode assembly (MEA) through both the development of new materials and the optimization of the 3D structural arrangement of individual MEA components [1,2] . Structural optimization of MEA remains to be challenging due to multiple materials interacting across 6 orders of magnitude in their characteristic length scales, from several nanometers for the catalyst particle size to hundreds of micrometers for carbon fibers in porous transport layer. In recent years, several microscopy techniques have become widely available to characterize the three-dimensional (3D) structure of PEMFC catalyst layers. Due to the heterogeneous nature of the PEMFCs sample, a correlative, multi-scale imaging protocol is developed in this work. The following technology is used where their corresponding resolution limit is pushed. Transmission Electron Microscope tomography, TEMt [3] (0.60nm X 0.60nm X 0.60nm Voxel Size) Focussed Ion Beam - Scanning Electron Microscope tomography, FIB-SEM [4] (2.5nm X 2.5nm X20 nm Voxel Size) Micro and Nano X-ray Computed Tomography, NanoCT [5] (367nm X 367nm X 367nm Voxel Size) Each technique by itself supports valuable insight to be obtained on the investigated structure at the corresponding length scale. By combining 3D imaging data at multiple scales, an unified structural characterization workflow is developed. Furthermore, an up scaling approach is developed based on TEMt, SEM and NanoCT reconstruction of catalyst layer, micro-porous layer and porous gas transport layer of a PMEFC cathode. Structural properties and effective transport properties are computed at each scale via image-based numerical simulation. Effective transport properties are up-scaled. MEA performances are predicted based on the obtained effective quantities at micro-scale.

Renewable energies and fuel cell technologies will likely play a major role in reducing our dependency on fossil fuels. In particular, proton exchange membrane fuel cells (PEMFCs) are suitable for use in both domestic and automotive applications. This sophisticated technology requires a functional nanostructured material that contains platinum to catalyse both the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) to produce water, electricity, and heat. [1] Unfortunately, in spite of their remarkable potential, the high cost and degradation of platinum‐based catalytic materials have been a barrier to widespread adoption of this type of technology. Reducing platinum content while simultaneously improving the durability will therefore require novel approaches in the catalyst design and its characterization at nanoscale level. [2]Transmission Electron Microscopy (TEM) techniques have continued to play a major role in the design and characterization of PEMFC materials. Using an aberration‐corrected microscope (Titan cubed 80‐300), we investigated the structural stability over the lifetime of a proposed fuel cell cathode material containing nano‐particulate platinum on a NbOx‐carbon hybrid support. The characterization of this material included a series of ex‐situ TEM analyses before or after accelerated stress tests that cycled the sample 30,000 times between 0.6 and 1.0 V in an electrochemical cell.The histograms shown in Fig1a and b reveal that some metal particle coarsening occurred during the 30,000‐cycle test. The as‐prepared catalyst contained 1–5 nm particles, the majority of which were determined to be bimetallic, as determined by electron energy loss spectroscopy (EELS), with some Pt‐rich particles and Nb‐rich grains (Fig. 1c). After 30,000 cycles, microanalysis data confirms that the cycling treatment caused some agglomeration of the small Pt‐rich particles. Analysis of the EELS oxygen K ionization edge indicates that multiple niobium oxidation states are present in the system, predominantly Nb(V) before electrochemical cycling (Fig 1c). Although conventional image comparisons between the initial and final state of the hybrid catalyst suggest that the Pt particle size increased marginally, in order to obtain an improved understanding of the material's degradation, morphological and structural evolution of the particles and hybrid support were tracked using the so‐called Identical Location TEM technique [3]. The results in figure 2 indicate that no large‐scale degradation of the hybrid support took place, suggesting carbon corrosion was minimized. In addition, only minor changes occurred to the average particle size, demonstrating the excellent stability of the metallic particles. These findings demonstrate that highly dispersed Pt/NbOxon carbon support material is a promising electrocatalyst for PEMFC.

Proton exchange membrane (PEM) fuel cells are being developed as alternative energy sources for both residential and automotive application. In order for this technology to become fully commercial, the reduction of cost and improvements in performance and durability of PEM fuel cells membrane electrode assemblies (MEAs) are still required. To address the requirement for further cost reduction the Pt loading of the cathode catalyst layer (CCL) needs to be reduced to 0.2- 0.1 mg/cm2 while maintaining high efficiency of Pt-utilization at high power densities. Consequently, it becomes increasingly important to not only develop new catalyst materials, but also optimize the 3D structural arrangement of the CCL components such as catalyst, ionomer and void space so that all critical functionalities can be achieved simultaneously and optimize PGM utilization. In general terms this entails to provide sites catalytically active for ORR, and to further provide transport to/these sites for the reactants O2, protons, electrons and products H2O and heat, respectively. In order to be able to design CCL structures that meet the performance and durability requirements, it is necessary to obtain a better understanding of structure versus performance relationships. This requires the capability to fabricate different CCL structures, to characterize the spatial distribution of all components within the catalyst layer1,2 (carbon, Pt, ionomer and void), to measure the physico-chemical properties (both ex-situ and in-situ) and finally to use these experimental data as inputs for the development a model based understanding of the relationship between CCL structure and CCL performance and durability3. References A. P. Hitchcock, V. Berejnov, V. Lee, D. Susac and J. Stumper, “In situ methods for analysis of polymer electrolyte membrane fuel cell materials by soft X-ray scanning transmission x-ray microscopy”, Microscopy & Microanalysis 20(S3) 1532 (2014)V. Lee, V. Berejnov, M. West, S. Kundu, D. Susac, J. Stumper, R.T. Atanasoski, M. Debe and A.P. Hitchcock, “Scanning Transmission X-ray Microscopy of Nano Structured Thin Film Catalysts for Proton-Exchange-Membrane Fuel Cells” J. Power Sources 263 163 (2014)S. G. Rinaldo, W. Lee, J Stumper, M. Eikerling: “Nonmonotonic dynamics in Lifshitz-Slyozov-Wagner theory: Ostwald ripening in nanoparticle catalysts” Physical Review E 86, 041601 (2012)