Platinum-Based Nanocatalysts for Proton Exchange Membrane Fuel Cells

Fuel cells have potential to become an integral technology in a future sustainable energy system. For transport applications, the proton exchange membrane fuel cell (PEMFC) is the most promising option, exhibiting light weight and high energy density. However, large-scale commercialization is impeded by expensive catalyst materials and slow oxygen reduction reaction (ORR) kinetics on the cathode side. Several alternatives to the conventional platinum PEMFC catalyst have been proposed and studied during the last decades, one being platinum-rare earth (Pt-RE) metal alloys. With enhanced ORR activities and maintained stability, these materials are highly interesting for deployment in PEMFCs, and could potentially reduce both catalyst material use and overall fuel cell cost. In practical fuel cells, catalysts are required in nanoparticulate form, to facilitate sufficient performance while keeping material utilization high. Unfortunately, scalability remains as a main obstacle for Pt-RE nanoparticle synthesis, as fabrication of these materials has proven challenging, motivated by the high oxygen affinity of the rare-earth metals.This thesis investigates the use of sputtering onto liquid (SoL) substrates as a potential synthesis method for Pt-RE nanocatalysts. The influence of sputtering parameters, including substrate type and temperature, as well as gas environment, on the size and morphology of platinum-based nanocatalysts are studied. Transmission electron microscopy of platinum sputtered in four different liquids indicates that the size of the nanoparticles is only weakly dependent on temperature. Furthermore, catalyst layers fabricated from the SoL-synthesized nanocatalysts are evaluated in a half cell setup. The electrochemical results shows that high performing catalyst layer fabrication from SoL-synthesized nanoparticles is viable, which opens for further development of the technique

Plasma-Induced Heating Effects on Platinum Nanoparticle Size during Sputter Deposition Synthesis in Polymer and Ionic Liquid Substrates

Nanoparticle catalyst materials are becoming ever more important in a sustainable future. Specifically, platinum (Pt) nanoparticles have relevance in catalysis, in particular, fuel cell technologies. Sputter deposition into liquid substrates has been shown to produce nanoparticles without the presence of air and other contaminants and the need for precursors. Here, we produce Pt nanoparticles in three imidazolium-based ionic liquids and PEG 600. All Pt nanoparticles are crystalline and around 2 nm in diameter. We show that while temperature has an effect on particle size for Pt, it is not as great as for other materials. Sputtering power, time, and postheat treatment all show slight influence on the particle size, indicating the importance of temperature during sputtering. The temperature of the liquid substrate is measured and reaches over 150 \ub0C during deposition which is found to increase the particle size by less than 20%, which is small compared to the effect of temperature on Au nanoparticles presented in the literature. High temperatures during Pt sputtering are beneficial for increasing Pt nanoparticle size beyond 2 nm. Better temperature control would allow for more control over the particle size in the future

Plasma cells and Fc receptors in human adipose tissue--lipogenic and anti-inflammatory effects of immunoglobulins on adipocytes

We have previously reported high immunoglobulin expression in human omental adipose tissue. The aim of this work was to investigate plasma cell density and Fc receptor (FcR) expression in human adipose tissue depots and in vitro effects of immunoglobulins on adipocyte function. Plasma cell density was higher in the visceral compared to the subcutaneous depot (10.0+/-1.56% and 5.2+/-0.98%, respectively, n=20,

High expression of complement components in omental adipose tissue in obese men.

OBJECTIVE: Accumulation of visceral fat is recognized as a predictor of obesity-related metabolic disturbances. Factors that are predominantly expressed in this depot could mediate the link between visceral obesity and associated diseases. RESEARCH METHODS AND PROCEDURES: Paired subcutaneous and omental adipose tissue biopsies were obtained from 10 obese men. Gene expression was analyzed by DNA microarrays in triplicate and by real-time polymerase chain reaction. Serum C3 and C4 were analyzed by radial immunodiffusion assays in 91 subjects representing a cross section of the general population. Body composition was measured by computerized tomography. RESULTS: Complement components C2, C3, C4, C7, and Factor B had higher expression in omental compared with subcutaneous adipose tissue ( approximately 2-, 4-, 17-, 10-, and 7-fold, respectively). In addition, adipsin, which belongs to the alternative pathway, and the classical pathway components C1QB, C1R, and C1S were expressed in both depots. Analysis of tissue distribution showed high expression of C2, C3, and C4 in omental adipose tissue, and only liver had higher expression of these genes. Serum C3 levels correlated with both visceral and subcutaneous adipose tissue in both men (r = 0.65 and

Depot-specific expression of fibroblast growth factors in human adipose tissue.

We have investigated the expression of several fibroblast growth factors (FGFs) and FGF-receptors (FGFRs) in human adipose tissue and adipose-tissue cell fractions obtained from both subcutaneous (sc) and omental (om) depots