Modeling Fluid Flow in the Gas Diffusion Layers in PEMFC Using the Multiple Relaxation‐time Lattice Boltzmann Method

The gas diffusion layers (GDLs) are key components in proton exchange membrane fuel cells and understanding fluid flow through them plays a significant role in improving fuel cell performance. In this paper we used a combination of multiple‐relaxation time lattice Boltzmann method and imaging technology to simulate fluid flow through the void space in a carbon paper GDL. The micro‐structures of the GDL were obtained by digitizing 3D images acquired by X‐ray computed micro‐tomography at a resolution of 1.76 μm, and fluid flow through the structures was simulated by applying pressure gradient in both through‐plane and in‐plane directions, respectively. The simulated velocity field at micron scale was then used to estimate the anisotropic permeability of the GDL. To test the method, we simulated fluid flow in a column packed with glass beads and the estimated permeability was found to be in good agreement with experimental measurements. The simulated results for the GDL revealed that the increase of permeability with porosity was well fitted by the model of Tomadakis–Sotirchos [48] without fitting parameters. The permeability calculated using fluids with different viscosities indicated that the multiple‐relaxation time lattice Boltzmann method provides robust solutions, giving a viscosity‐independent permeability. This is a significant improvement over the commonly used single‐time relaxation lattice Boltzmann model which was found to give rise to a unrealistic viscosity‐dependent permeability because of its inaccuracy in solving the fluid–solid boundaries.     

Catalysts for Direct Methanol Fuel Cells

The activity of in house prepared carbon-supported Pt-Ru catalysts for methanol oxidation and carbon-supported RuSe for the oxygen reduction reaction in direct methanol fuel cells (DMFCs) was investigated. The composition of Pt-Ru/C was varied both in terms of weight loading (ratio of total metal content to carbon) as well as the ratio of Pt to Ru. The measurements were carried out in a half cell arrangement in sulphuric acid at various temperatures. The weight loading and ratio of Pt to Ru were varied in order to find out the optimum weight loading of precious metal and the temperature dependence of Pt to Ru ratio on methanol oxidation reaction. It has been found that there exists an optimum in the weight loading at 60 wt.% for carbon-supported Pt-Ru catalyst towards its maximum mass activity. While 1:1 Pt to Ru ratio exhibits a higher activity than 3:2 Pt:Ru above 60 °C, 3:2 ratio exhibits a higher activity at lower temperature. It has been observed that RuSe is inactive towards methanol and it is realised that RuSe is a potential candidate as methanol tolerant oxygen reduction catalyst. The activity of carbon supported RuSe for oxygen reduction reaction (ORR) was tested in sulphuric acid in the presence of methanol. Even though the mass specific activity of the RuSe catalyst is somewhat lower than that of Pt/C, the surface activity of carbon-supported RuSe is superior than that of carbon supported Pt which indicate the unfavourable size distribution of RuSe/C catalyst.     

High Performance Carbon‐Supported Core@Shell PdSn@Pt Electrocatalysts for Oxygen Reduction Reaction

In this report, a low‐cost and high performance PdSn@Pt/C catalyst with core–shell structure is prepared by two‐stage route. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) examinations show that the composite catalyst particles distribution is quite homogeneous and has a high surface area and the PdSn@Pt/C catalyst has an average diameter of ca. 5.6 nm. The oxygen reduction reaction (ORR) activity of PdSn@Pt/C was higher than commercial Pt/C catalyst. Catalytic activity is studied by cyclic voltammetry. High electrocatalytic activities could be attributed to the synergistic effect between Pt and PdSn.     

Performance of the Direct Methanol Carbonate Fuel Cell Using Anion Exchange Materials and Non‐Noble Metal Cathode Catalyst

A direct methanol fuel cell using a mixture of O₂ and CO₂ at the cathode was evaluated using anion exchange materials and cathode catalysts of Pt and a non‐Pt catalyst. The MEA based on non‐noble metal catalyst Acta 4020 showed superior performance than Pt/C based MEA in terms of open circuit potential and power density in carbonate environment. The fuel cell performance was improved by applying anion exchange ionomer in the catalyst layer. A maximum power density of 4.5 mW cm^–2 was achieved at 50 °C using 6.0 M methanol and 2.0 M K₂CO₃.     

Influence of precursor deficiency sites for borate incorporation on the structural and biological properties of boronated hydroxyapatite

The biological properties of hydroxyapatite (HA) are significantly influenced by its compositional characteristics especially doping elements and/or Ca/P ratio, which can be altered by precursor chemistry. In this study, a group of boronated (B-incorporated) hydroxyapatite (BHA) was synthesized using a precipitation method by setting the Ca/P ratio to the stoichiometric value of HA (1.67), while altering the precursor chemistry by adjusting either (Ca + B)/P (Ca-deficient precursor, BC) or Ca/(P + B) (P-deficient precursor, BP). After heat-treatment, the partial decomposition of the BC was observed, forming tricalcium phosphate as the byproduct, however, the BP showed phase stability at all temperatures. The B-ionic species in the form of (BO₂)^? and (BO₃)^3? were incorporated into the HA structure at the (PO₄)^3? and (OH)^? positions, respectively. The incorporation of the B species also facilitated the incorporation of (CO₃)^2? groups specifically in the BPs. This is the first finding on BHA reporting that preferential (CO₃)^2? incorporation depends on the precursor chemistry used. As a result, osteoblast adhesion was superior on the BPs compared to pure HA owing to the carbonated structure, increasing cell spreading area. As such, this in vitro study highlighted that the present P-deficient precursor approach for synthesizing BHA improved biocompatibility properties and should, thus, be further considered for the next-generation of improved orthopedic applications.     

Nanosecond pulsed laser surface modification of yttria doped zirconia for Solid Oxide Fuel Cell applications: Damage and microstructural changes

An effective strategy to reduce the cathode polarization in a Solid Oxide Fuel Cell (SOFC) is to enlarge the cathode-electrolyte interface, corrugating the electrolyte surface of zirconia doped with 8 mol% of yttria (8YSZ) by pulsed-laser machining. However, laser-material interaction using a nanosecond pulsed laser can involve thermal effects on the surface. The objective of this work was to analyze the microstructural and phase changes, and the collateral damage caused by laser machining on the 8YSZ electrolyte surface of the SOFCs, and compare it with the 3% molar in yttria (3Y-TZP). Several patterns consisting in parallel tracks below 10 µm depth were investigated. The results evidenced a heat affected zone (HAZ) limited to ⁓1–2 µm with microcracking and directional recrystallization, which was larger in 8YSZ than in 3Y-TZP. However, the mechanical response near the HAZ and chemical composition at the machined surface was not significantly changed.     

Hydrogen for the Mobility of the Future Results of GM/Opel's Well‐to‐Wheel Studies in North America and Europe

General Motors conducted two well‐to‐wheel studies for fundamental clarification on the question of which is the cleanest and most environmentally sustainable source of energy for the mobility of the future. In both studies the complete energy chains were analyzed from fuel production using primary energy to the actual consumption of the fuel in the car, i.e. from the well up to the wheels of the vehicle (well to wheel). The aim of the studies was to evaluate total energy consumption on the one hand and, on the other, the total greenhouse gas emissions arising between the production of a fuel and its final use to power an automobile. The results of the studies clearly show that fuel cell vehicles can greatly reduce greenhouse gas emissions from passenger cars or, if they run on hydrogen from renewable energy sources, they can eliminate them entirely. Regenerative fuels, however, will be more expensive than current products. With the fuel cell, because of its superior efficiency (35 – 45% less energy consumption well to wheel), it will be possible to keep individual mobility affordable in the future.     

Effects of areca nut consumption on cell differentiation of osteoblasts,myoblasts, and fibroblasts

Areca nut is used worldwide as a hallucinogenic addicting drug along the tropical belt. Arecoline, a toxic compound, is the most important alkaloid in areca nuts. The adverse effects of oral uptake and chewing of areca nut are well known. For example, the possibility of cancer caused by chewing areca nuts is widely discussed. Chewing areca nut has other adverse effects on other organs, including abnormal cell differentiation, oral cancer, and several other diseases. The use of areca nut is also associated with low birthweight. Skeletal musculature is the largest organ in the body and is attached to the bones. During embryo development, the differentiation of bone and muscle cells is critical. In this article, we reviewed the effects of areca nut and arecoline on embryonic cell differentiation, particularly osteoblasts, myoblasts, and fibroblasts.