The direct borohydride fuel cell (DBFC) is one of several promising direct liquid fuel cells due to easy fuel handling and high energy storage density [1]. DBFCs are still in an early stage of development and further improvements of anode catalyst materials and MEA design are necessary for widespread application. Herein we present an extensive study of Palladium based catalysts for the anode reaction of DBFCs (see reaction 1) including several electrochemical experiments supported by 11B-NMR and FTIR measurements. BH4 - + 8OH- → BO2 - + 6H2O + 8e- (1) (E0 = -1.24 V vs. SHE) Palladium based electrocatalysts nanodispersed on high surface area carbon are prepared by reduction of precursor salts in an aqueous dispersion of the support material. The catalyst is characterized by transition electron microscopy (TEM). Rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) experiments with subsequent analysis of reaction products by 11B-NMR are conducted. Fig. 1 shows a typical result of Pd/C on a RDE with a borohydride concentration of 5 mM. Additionally mechanistic aspects on Palladium are investigated employing in-situ FTIR spectroscopy [2]. By combining all results obtained from the experiments mentioned above a substantial proposition of ongoing mechanisms of BH4 --electrooxidation on Palladium is presented. [1] J. Ma, N. a. Choudhury, Y. Sahai, Renew. Sustain. Energy Rev. 14 (2010) 183. [2] B.M. Concha, M. Chatenet, C. Coutanceau, F. Hahn, Electrochem. Commun. 11 (2009) 223. Caption Figure 1: RDE experiments of Pd/C catalyst at rotation rates of 0-2000 rpm (anodic sweeps) in 1M NaOH with 5 mM NaBH4, insert: according Levich-plot at 0.830 V. Figure 1
Available hydrogen production and storage technologies do not fulfil the economical, technical and environmental requirements of a hydrogen economy. Existing technological options are characterised and discussed. New technological solutions, investigated at the Institute of Chemical Engineering and Environmental Technologies of TU Graz, are presented. For hydrogen production with low environmental impact, the combination of production, purification and storage in one technology, the reformer-steam-iron process, is introduced. This process integrates conventional steam reforming with a chemical looping process in order to produce pure pressurised hydrogen. For storage a liquid chemical hydrogen storage system based on the borohydride anion is developed. The storage medium is either catalytically dehydrogenated, or is directly fed into a direct borohydride fuel cell. Index Terms-Fuel processing, fuel cells, decentralised power generation, steam-iron-process, ionic liquid. 1 METHOD -STORAGE DENSITYCompressed storage: 350 bar (type IV generation): 5.5wt%, 17.6 kgH2/m³, ambient temp. 700 bar (type IV generation): 5.2wt%, 26.3 kgH2/m³, ambient temp. Liquid storage: 5.6wt%, 70 kg/m3, 23.5 kgH2/m³, 1 bar, 21.15K. Cryo compressed: 5.5-9.2wt%, 41.8-44.7 kgH2/m³, >>1bar, 21.15K Metal Organic Framework MOF177: 4wt%, 34.6 kgH2/m³ Chemical Storage, storage at ambient temperature and pressure Sodium borohydride: 3wt%, 23 kgH2/m³ Alane 4.2wt%, 48 kgH2/m³ Ammonia borane 4.8wt%, 48 kgH2/m³
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