Chemically tuned anode with tailored aqueous hydrocarbon binder for direct methanol fuel cells.
ABSTRACT An anode for direct methanol fuel cells was chemically tuned by tailoring an aqueous hydrocarbon catalyst (SPI-BT) binder instead of using a conventional perfluorinated sulfonic acid ionomer (PFSI). SPI-BT designed in triethylamine salt form showed lower proton conductivity than PFSI, but it was stable in the catalyst ink forming the aqueous colloids. The aqueous colloidal particle size of SPI-BT was much smaller than that of PFSI. The small SPI-BT colloidal particles contributed to forming small catalyst agglomerates and simultaneously reducing their pore volume. Consequently, the high filling level of binders in the pores, where Pt-Ru catalysts are mainly located on the wall and physically interconnected, resulted in increased electrochemical active surface area of the anode, leading to high catalyst utilization. In addition, the chemical affinity between the SPI-BT binder and the membrane material derived from their similar chemical structure induced a stable interface on the membrane-electrode assembly (MEA) and showed low electric resistance. Upon adding SPI-BT, the synergistic effect of high catalyst utilization, improved mass transfer behavior to Pt-Ru catalyst, and low interfacial resistance of MEA became greater than the influence of reduced proton conductivity in the electrochemical performance of single cells. The electrochemical performance of MEAs with SPI-BT anode was enhanced to almost the same degree or somewhat higher than that with PFSI at 90 degrees C.
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ABSTRACT: Incidental renal masses are common findings on cross-sectional imaging. Most will be readily identified as simple cysts, but with an inexorable rise in abdominal imaging, [particularly computed tomography (CT)], coupled with a rise in the incidence of renal cancer, the likelihood of detecting a malignant mass is increasing. This review informs the radiologist which lesions can be safely ignored, which will require further imaging for accurate categorization, and which require referral for consideration of treatment. For the small proportion of lesions that are indeterminate, careful attention to imaging technique, and the use of unenhanced and contrast-enhanced CT or magnetic resonance imaging (MRI) in all but a few specific instances will accurately characterize such lesions. The figures have been chosen to illustrate specific imaging features of common renal lesions. Management options for malignant, or presumed malignant, renal masses include active surveillance, percutaneous ablation, laparoscopic or open, partial or total nephrectomy. Biopsy has a role in determining the nature of masses that remain indeterminate on cross-sectional imaging, prior to definitive treatment. Common pitfalls in assessing incidental renal lesions are emphasized; some of these are due to sub-optimal imaging techniques and others to errors in interpretation.Clinical Radiology 08/2011; 66(12):1129-39. · 1.66 Impact Factor
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ABSTRACT: Hydrocarbon ionomers have not been successfully employed in the cathode of polymer electrolyte fuel cell (PEFC)s due to their low oxygen permeabilities. In this work, we propose a partially fluorinated aromatic polyether with sulfonic acid groups (s-PFPE) as an ionomer for the cathode catalyst layer. Compared to sulfonated poly(ether ether ketone) (s-PEEK), it exhibited more than 1.5 times higher oxygen permeability at RH 40% and 1.3 times higher at RH 100%. The catalyst layer based on s-PFPE showed higher power performance than that based on s-PEEK owing to enhanced oxygen transport and fast proton conduction through the s-PFPE ionomer phase covering the catalyst layer. We demonstrate that the introduction of the perfluorinated moieties to the hydrocarbon backbone is an effective strategy for the use of hydrocarbon ionomer in the cathode of PEMFCs.Electrochimica Acta 04/2014; 125:314–319. · 4.09 Impact Factor