Ethanol Fuel as Portable Power Source in Alkaline Fuel Cells Prof. Shingjiang Jessie Lue Chair and professor, Department of Chemical and Materials Engineering Group leader, Green Technology Research Center Chang Gung University, Taiwan

Fuel cell cars powered by bioethanol: Green energy H2 + O2  H2O + i Chemical energy  electricity Oxidation/combustion of fuels Spontaneous reaction Catalysts speed up reaction rate (more electrons generated; higher electrical current)

Various process steps for biomass conversion to ethanol and co-products Badwal et al., Appl. Energ. 145 (2015) 80.

Various sources of ethanol, energy output/ input ratios and commercial status Source type Sources Energy output/input ratio Commercialization stage Food crops Corn Wheat Barley Sugarcane Sugar beet Cassava Sorghum Corn: 1.4, 2a and 2.8b Sugarcane:~8 (Brazil) Sugar beet: 2 Commercial plants of ethanol mainly from corn (US) and sugarcane Inedible parts of plant-cellulosic ethanol Corn stover Wheat straw Rice straw Sugarcane bagasse 5.2–5.54 5.2 – 32 Pre-commercial stage, pilot scale or demonstration plants with subsidies and local government support Cellulosic ethanol-others Switch grass Poplar Forest residue Agricultural waste Municipality waste 2–36 Pilot scale or demonstration plants with subsidies and local government support a For ‘‘a dry grind ethanol plant that produces and sells dry distiller’s grains and uses conventional fossil fuel power for thermal energy and electricity’’. b For ‘‘a dry grind ethanol plant that produces and sells dry distiller’s grains and uses’’ 50% biomass power. Badwal et al., Appl. Energ. 145 (2015) 80.

Potential fuels: hydrogen and alcohols Badwal et al., Appl. Energ. 145 (2015) 80.

Electrochemical reactions involved in various types of alcohol fuel cells Badwal et al., Appl. Energ. 145 (2015) 80.

Proton- and hydroxide-conducting DEFCs Acid Alkaline C2H5OH + 3O2 → 2 CO2 + 3 H2O Eo=1.14 V, ΔGo= -1325 kJ mol–1 C2H5OH + 3O2 → 2 CO2 + 3 H2O Eo=1.14 V, ΔGo= -1325 kJ mol–1 Disadvantages: Ethanol cross-over -- Fuel loss -- Mixed cell potential Expensive Pt based catalyst Proton exchange membrane Advantages: Faster ethanol oxidation rate in alkaline media Can use less expensive non-Pt catalysts Direction of OH− anion motion opposes ethanol permeability: less EtOH cross-over Easy water management Front. Energy Power Eng. China 4 (2010) 443; J. Membr. Sc. 367 (2011) 256.

Electrochemical performance Polarization curve (V-I curve) Voc (open-circuit voltage): governed by catalytic activity and fuel cross-over rate Ohmic loss: governed by cell electric resistance (esp. membrane electrolyte) Power density curve (P-I curve) P=VI Pmax (peak power density): more reproducible than Voc Pmax: indicator of fuel cell performance http://www.intechopen.com/

DEFC performance reported in literatures An et al., Renew. Sust. Energ. Rev. 50 (2015) 1462.

DEFC prototype stack 1 kW DEFC stack (by NDC Power) Badwal et al., Appl. Energ. 145 (2015) 80.

Prepare and synthesize frontier materials for energy applications Our Research Focuses Prepare and synthesize frontier materials for energy applications Solar cell Working Mechanism of Alkaline Alcoholic Fuel Cells O2+H2O CO2+H2O C2H5OH+KOH Nanocomposite Membrane C2H5OH Anode: C2H5OH+12OH-→2CO2+9H2O+12e- Cathode: 3O2+6H2O+12e-→12OH- Overall: C2H5OH+3O2→2CO2+3H2O Energy Applications Fuel cell Lithium-air battery Membrane Requirements : High conductivity and low fuel permeability

Hydroxide transport mechanisms Vehicular diffusion Hopping mechanism Surface diffusion Polymer/anion-exchange moiety Polymer/carbon nano-tubes Polymer/nano-fillers

Our Membrane Electrolyte Development Strategy Nafion/GO PBI/GO PVA/CNT PBI/CNT Q-PVA/Q-chitosan Pristine GO Blend with Q-chitosan nanoparticles J. Polym. Sci. Phys. 51 (2013) 1779 J. Membr. Sci. 376 (2011) 225 J. Power Sources 202 (2012) 1 J. Power Sources 246 (2014) 39 GO on Nafion J. Membr. Sci. 485 (2015) 17 J. Membr. Sci. 493 (2015) 212

Single cell assembly and test Fuel/KOH MEA (membrane electrode assembly) Anode (catalyst on gas diffusion electrode): Pt-Ru/C or non-Pt/C on carbon cloth Membrane electrolyte Cathode (catalyst on gas diffusion electrode): Pt/C or non-Pt on carbon cloth

Sulfonated styrene-ethylene-butylene-styrene DEFC performance: PTFE/sSEBS at 30ºC Pmax = 7.6 mW cm-2 at 60ºC Sulfonated styrene-ethylene-butylene-styrene block copolymer Pmax = 17 mW cm-2 Anode: PtRu/C (6 mg cm-2) Cathode: Pt/C (5 mg cm-2) J. Membr. Sci. 464 (2014) 43. DEFC at 30 and 60ºC

DEFC performance: Graphene oxide (GO)/Nafion Pmax = 35 mW cm-2 Anode: PtRu/C (6 mg cm-2) Cathode: Pt/C (5 mg cm-2) J. Membr. Sci. 493 (2015) 212. 3 M ethanol at 80ºC

ADEFC performance: polyvinyl alcohol/ carbon nanotubes (PVA/CNT) Fractional free volume: 2.48 to 3.53% (containing CNT) at 30ºC at 60ºC Pmax = 33 mW cm-2 Pmax = 65 mW cm-2 J. Power Sources, in review. ADEFC in 5 M KOH Anode: PtRu/C (6 mg cm-2), cathode: Pt/C (5 mg cm-2)

ADEFC performance: Q-PVA/Q-chitosan Anode: PtRu/C (6 mg cm-2) Cathode: Pt/C (5 mg cm-2) EtOH Pmax = 59 mW cm-2 Anode: PdCeO2/C (6 mg cm-2) Cathode: CuFe/C(5 mg cm-2) Pmax = 20 mW cm-2 J. Membr. Sci. 485 (2015) 17. 3 M ethanol in 5 M KOH

ADEFC performance: GO/PBI Non Pt-based catalyst Pt-based catalyst Anode: PdCeO2/C (6 mg cm-2) Cathode: CuFe/C 5 mg cm-2) Anode: PtRu/C (6 mg cm-2) Cathode: Pt/C (5 mg cm-2) Pmax = 120 mW cm-2 Pmax = 100 mW cm-2 3 M ethanol in 5 M KOH J. Membr. Sci. In preparation.

Our Alkaline Fuel Cell Performance

Conclusion Ethanol is a potent fuel source for direct alcohol fuel cells We have designed various nanocomposite electrolytes for acidic and alkaline DEFCs Our alkaline DEFC reached peak power density of 120 mW cm-2 Continued investigation on stable, high-performance catalysts on ethanol oxidation and oxygen reduction reactions is in strong demand An et al., Renew. Sust. Energ. Rev. 50 (2015) 1462.

Acknowledgements Ministry of Science and Technology, Taiwan Chang Gung Hospital Project Mr. Bor-Chern Yu, Mr. Guan-Ming Liao, Ms. Pin-Chieh Li, Ms. Jia-Shiun Lin, Dr. Hsieh-Yu Li, Dr. Chao-Ming Shih, Dr. Rajesh Kumar

Thank you for your attention!