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RISS 인기검색어
- 검색키워드
- 저자 : Brela, Mateusz (검색결과 2 건)
- 무료
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Anion conducting polymers based on ether linked polybenzimidazole (PBI-OO)
Henkensmeier, D.,Cho, H.,Brela, M.,Michalak, A.,Dyck, A.,Germer, W.,Duong, N.M.H.,Jang, J.H.,Kim, H.J.,Woo, N.S.,Lim, T.H. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.6
Anion conducting polymers are potentially interesting for fuel cells, electrochemical pumps, and dye sensitized solar cells. Ether-containing polybenzimidazoles (PBI-OO and PBI-OPO) were synthesized and turned into anion conducting polymers by methylation. The thermal stability was shown to depend on the polymer structure and degree of methylation (dom). Tensile strength and modulus decrease between 50% and 75% dom, but stay constant or slightly increase over 75% dom again. At 65 <SUP>o</SUP>C, hydroxide, iodide, chloride, carbonate and bicarbonate conductivities of 0.1, 0.6, 19, 20, 31 mS/cm were obtained, respectively. The low hydroxide conductivity is due to the formation of a C-O bond in position 2 of the imidazolium, which reduces the number of free ions and is known to lead to imidazolium ring opening and further degradation steps. The effect of introduction of phenoxy groups into the main chain on the charge distribution, especially on position 2 and the methyl groups (positive charge on the methyl groups decreases the thermal stability), as well as on the ion bonding was thoroughly investigated by DFT calculations and correlated with experimental data.
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Tetrazole substituted polymers for high temperature polymer electrolyte fuel cells
Henkensmeier, Dirk,Duong, Ngoc My Hanh,Brela, Mateusz,Dyduch, Karol,Michalak, Artur,Jankova, Katja,Cho, Hyeongrae,Jang, Jong Hyun,Kim, Hyoung-Juhn,Cleemann, Lars N.,Li, Qingfeng,Jensen, Jens Oluf The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.27
<▼1><P>Tetrazole (TZ) has lower basicity than imidazole and may not be fully protonated by phosphoric acid. DFT calculations suggest that the basicity of TZ groups can be increased by introducing a 2,6-dioxy-phenyl-group in position 5.</P></▼1><▼2><P>While tetrazole (TZ) has much lower basicity than imidazole and may not be fully protonated in the presence of phosphoric acid (PA), DFT calculations suggest that the basicity of TZ groups can be increased by the introduction of a 2,6-dioxy-phenyl-group in position 5 of TZ. This structure allows hydrogen bonds between TZ protons and ether oxygen atoms, and thereby establishes a resonance stabilised, co-planar structure for tetrazolium ions. Molecular electrostatic potential (MEP) calculations also indicate that tetrazolium ions possess two sites for proton hopping. This makes such materials interesting for use in a high temperature fuel cell (HT PEMFC). Based on these findings, two polymers incorporating the proposed TZ groups were synthesised, formed into membranes, doped with PA and tested for fuel cell relevant properties. At room temperature, TZ-PEEN and commercial <I>meta</I>-PBI showed an equilibrium uptake of 0.5 and 4.7 mol PA per mol heterocycle, respectively, indicating that PBI has higher affinity for PA than TZ-PEEN. The highest achieved PA uptake was <I>ca.</I> 110 wt%, resulting in a proton conductivity of 25 mS cm<SUP>−1</SUP> at 160 °C with a low activation energy of about 35 kJ mol<SUP>−1</SUP>. In a first HT PEMFC test at 160 °C, a peak power density of 287 mW cm<SUP>−2</SUP> was achieved.</P></▼2>
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