Bjerrum, Niels

Jensen, Jens Oluf

Li, Qingfeng

Vassiliev, Anton

A high temperature polybenzimidazole (PBI) polymer fuel cell was fed with dimethyl ether (DME) and water vapour mixture on the anode at ambient pressure with air as oxidant. A peak power density of 79 mW/cm2 was achieved at 200°C. A conventional polymer based direct DME fuel cell is liquid fed and suffers from low DME solubility in water. When the DME - water mixture is fed as vapour miscibility is no longer a problem. The increased temperature is more beneficial for the kinetics of the direct oxidation of DME than of methanol. The Open Circuit Voltage (OCV) with DME operation was 50 to 100 mV higher than that of methanol, indicating less fuel crossover

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Downloaded from orbit.dtu.dk on: Dec 20, 2017Direct dimethyl ether high temperature polymer electrolyte membrane fuel cellsVassiliev, Anton; Jensen, Jens Oluf; Li, Qingfeng; Bjerrum, Niels J.Publication date:2012Link back to DTU OrbitCitation (APA):Vassiliev, A., Jensen, J. O., Li, Q., & Bjerrum, N. (2012). Direct dimethyl ether high temperature polymerelectrolyte membrane fuel cells. Poster session presented at Energieffektivisering for fremtiden, Kgs.Lyngby,Denmark.Direct dimethyl ether high temperature  polymer electrolyte membrane fuel cells Anton Vassiliev*, Jens Oluf Jensen, Qingfeng Li and Niels J. Bjerrum Proton Conductors, Department of Energy Conversion and Storage,  Technical University of Denmark, Kemitorvet 207, DK-2800 Lyngby, Denmark *anvas@dtu.dk DME Methanol Ethanol DME is: • A clean colourless gas • Liquid at 6 bar(a)  - handled like LPG • Little or not toxic • Not a greenhouse gas      - decomposes in atmosphere      in tens of hours)  As a fuel: • Cetane rating 55 – 60   (45 for petroleum-derived diesel) • Burns with no particulate matter (soot) • Very low NOx, no SOx • Excellent diesel engine fuel   Manufacture: • From biomass • From syngas    Methane  Methanol  Dimethyl ether  Ethanol  Gasoline  Diesel Formula  CH4 CH3OH CH3OCH3 CH3CH2OH C7H16 C14H30  LHV  (kJ cm−3)  0.0346 15.82 18.92 21.09  32.05 35.66  LHV  (kJ g−1)  47.79 19.99 28.62 26.87 43.47 41.66  Boil.p (◦C) −162 64 −24.9 78 38–204 125–400 http://www.aboutdme.org Outline A high temperature polybenzimidazole (PBI) polymer fuel cell was fed with dimethyl ether (DME) and water vapour mixture on the anode at ambient pressure with air as oxidant. A peak power density of 79 mW/cm2 was achieved at 200 C. A conventional polymer based direct DME fuel cell is liquid fed and suffers from low DME solubility in water. When the DME - water mixture is fed as vapour miscibility is no longer a problem. The increased temperature is more beneficial for the kinetics of the direct oxidation of DME than of methanol. The Open Circuit Voltage (OCV) with DME operation was 50 to 100 mV higher than that of methanol, indicating less fuel crossover. References 1.     T. A. Semelsberger, R. L. Borup, H. L. Greene, J. Power Sources 156, 497 (2006). 2.     J. T. Muller et al., J. Electrochem.Soc. 147, 4058 (2000). 3.     R. H. Yu, H. G. Choi, S. M. Cho, Electrochem. Comm. 7, 1385 (2005). 4.     M. M. Mench, H. M. Chance, C. Y. Wang, J. Electrochem. Soc. 151, A144 (2004). 5.     J. Y. Im, B. S. Kim, H. G. Choi, S. M. Cho, J. Power Sources 179, 301 (2008). 6.     Y. Tsutsumi, Y. Nakano, S. Kajitani, S. Yamasita, Electrochem. 70, 984 (2002). 7.     K. D. Cai, G. P. Yin, L. L. Lu, Y. Z. Gao, Electrochem. Solid State Letters 11, B205 (2008). 8.     I. Mizutani, Y. Liu, S. Mitsushima, K. I. Ota, N. Kamiya, J. Power Sources 156, 183 (2006). 9.     S. Ueda, M. Eguchi, K. Uno, Y. Tsutsumi, N. Ogawa, Solid State Ionics 177, 2175 (2006). 10.   Y. Zhang, Y. J. Tong, L. L. Lu, M. Osawa, S. Ye, J. Electrochem. Soc. 157, F10 (2010). 11.   J. S. Wainright, J. T. Wang, D. Weng, R. F. Savinell, M. Litt, J. Electrochem. Soc. 142, L121 (1995). 12.   Q. F. Li, J. O. Jensen, R. F. Savinell, N. J. Bjerrum, Prog. Polym. Sci. 34, 449 (2009). DME is normally fed as an aqueous  solution in conventional PEM fuel cells.  Anode reaction:          CH3OCH3 + 3H2O → 2CO2 + 12H+ + 12e-  DME-water ratio required 1:3 ⇒ 46 wt% solution of DME in water, but DME solubility is only ca. 7.6 wt% at 20°C(2). At  80°C of a traditional polymer fuel cell operation temperature the solubility is even lower and a saturated DME-solution separates into two phases (3). This impedes the process.    By increasing the working temperature above the boiling point of water and feeding the DME-water mixture as vapour  the miscibility is no longer a problem.  A phosphoric acid doped PBI system has operation  range of 120-200 °C (11,12) and  is thus well-suited  for the purpose. MEAs hot-pressed •  Anode 40 wt% Pt, 20 wt% Ru, 40 wt% C,     Johnson Matthey •  Cathode 60 wt% Pt, 40 wt% C,     Johnson Matthey •  Electrolyte 40 µm H3PO4-doped PBI    membrane, Danish Power Systems •  Protective polysulfone film Operating conditions •  150 or 200 °C •  32 mL/min DME and 0.07 mL/min H2O •  0.23 mL/min 1:1 molar MeOH-water  DME powered diesel truck from Volvo Further on DME: Performance curves of a direct DME fuel cell based on acid doped PBI at 200 C. Ambient pressure, air as oxidant. Comparison of direct fuelling with DME and methanol at 150 C (lower) and 200 C (upper). Anode catalyst: PtRu/C (Johnson-Matthey, 1:1, 60 wt%, 4.0 mg metal pr cm2) Cathode catalyst: Pt/C (Johnson-Matthey, 60 wt%, 0.7 mg Pt pr cm2) Schematic setup Acknowledgements  The Danish Agency for Science, Technology and Innovation  (Vedvarende Energiteknologier)  Danish Power Systems Publication J. O. Jensen, A. Vassiliev, M. I. Olsen, Q. Li, C. Pan, L. N. Cleemann, T. Steenberg, H. A. Hjuler and N. J. Bjerrum, Direct Dimethyl Ether Fuelling of a High Temperature Polymer Fuel Cell, J. Power Sources 211 173-176 (2012). 0 10 20 30 40 50 60 70 80 90 100 0 0,01 0,02 0,03 0,04 0,05 Temperature (°C) Molar fraction of DME in water  ○ Pure water  ● Mizutani 2006  ■ Holdorff 1998  ♦ Gerrard 1972 T = -14.87ln(x) - 36.41 Single cell, MEAs and cell housing.  0 10 20 30 40 50 60 70 80 90 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 0 100 200 300 400 500 600 700 800 900 Power denisty (mW/cm²) Voltage (V) Current density (mA/cm²) Dimethyl ether  Other uses: • Aerosol propellant • Cooking gas • Refrigerating agent Direct conversion in a PEMFC Equilibrium molar fractions of DME in water at different temperatures. Experimental 0 10 20 30 40 50 60 70 80 90 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 0 100 200 300 400 500 600 700 800 Power density (mW/cm²) Voltage (V) Current  density (mA/cm²) Results Effect of air (lower) vs. oxygen (upper)  at ambient pressure as oxidants on direct DME performance. 0 10 20 30 40 50 60 70 80 90 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 0 100 200 300 400 500 600 700 800 Power density (mW/cm²) Voltage (V) Current  density (mA/cm²) MeOH DME Peak power densities reported with conventional polymer  fuel cells: •  Ambient pressure, air as oxidant: 20 to 40 mW/cm² (3-5).  •  Ambient pressure, pure oxygen:  30 to 56 mW/cm² (6-10).  For most applications only air is available. The two-phase problem can be avoided by pressurizing the system, but this consumes energy and is not an attractive option for direct fuel cell systems which are meant to be simple.  One of the major drawbacks of direct methanol fuel cells is the methanol crossover. DME crossover is less pronounced in hydrophilic environment due to the lower dipole moment.  

Direct dimethyl ether high temperature polymer electrolyte membrane fuel cells

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Direct dimethyl ether high temperature polymer electrolyte membrane fuel cells

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