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‘Direct’ alcohol fuel cells:

‘Direct’ alcohol fuel cells:. E o cell (V) n = 1 [MeOH] 1.20 n = 2 [EtOH] 1.14. 6n e –. 6n H + ; H 2 O. n CO 2,(g). 3n H 2 O. C n H 2n+1 OH. (3n/2) O 2. C n H 2n+1 OH + (2n – 1) H 2 O. PEM. Anode (-). Cathode (+). PEM: proton exchange membrane.

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‘Direct’ alcohol fuel cells:

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  1. ‘Direct’ alcohol fuel cells: Eocell (V) n = 1 [MeOH] 1.20 n = 2 [EtOH] 1.14 6n e– 6n H+; H2O n CO2,(g) 3n H2O CnH2n+1OH (3n/2) O2 CnH2n+1OH + (2n – 1) H2O PEM Anode (-) Cathode (+) PEM: proton exchange membrane

  2. ‘Direct’ borohydride fuel cell: 8e- Eocell (V) 1.64 NaBO2 + 6H2O 8 Na+; H2O 4H2,(g) H2O 8NaOH NaBH4 + 2H2O 2O2 NaBH4 + 8NaOH PEM Anode (-) Cathode (+) PEM: proton exchange membrane

  3. Highlights of direct fuel cells • Advantages • Ethanol and methanol are primary liquid fuels obtainable from renewable, agricultural, resources: sustainable energy • Canada is a leader in both ethanol (~240 million liters annually from agricultural resources) and methanol production (Methanex) • The borohydride fuel cell (DBFC) is a zero-carbon emission power source • Higher theoretical energy densities compared to H2: H2-O2 fuel cell: 550 kWh m-3H2 (at 200 atm, 293 K) • DMFC 4,800 kWh m-3CH3OH • DEFC 6,300 kWh m-3C2H5OH • DBFC 2,000 kWh m-3(20% wt NaBH4 in 2 M NaOH)

  4. DisadvantagesProblems to be solved • Poor anode performance • Sluggish fuel electro-oxidation kinetics / electrocatalysis • CH3OH oxidation: Pt-Ru • C2H5OH oxidation: Pt-Sn • NaBH4 oxidation: Au, Pt, Metal-Hydrides • Effect of catalyst composition, operating conditions • Low catalyst layer utilization efficiency • Catalyst preparation method particle size dispersion on and interaction with various supports ionomer network / catalyst interface • Two-phase flow in the porous anode • For alcohol fuel cells: CO2 disengagement from the catalyst layer mass transfer overpotential and effective ionic conductivity • Fuel crossover from the anode to the cathode • Membrane permeable to alcohols mixed potential on the cathode

  5. Research strategy Surface analytical studies: - surface area, composition etc. Cell Design variables Colloidal precursor method Liquid crystal templated /surfactant assisted electrodep. Nano-scale electrocatalyst synthesis and deposition on substrates Evaluation of electro-catalytic activity Fuel cell testing and optimization Electrochemical methods: Voltammetry, impedance, chrono-techniques Electrodeposition from microemulsions and micellar media Operating conditions

  6. ~ 100 – 300 m Typical gas diffusion anode structure for direct fuel cells:Might not be the best engineering solution we are looking at alternatives ~ 5 – 25 m CO2,(g) H2O H+; H2O; R-OH C A T H O D E NaBO2, H2,(g) CH3OH, C2H5OH O2 Na+; H2O; ~BH4- NaBH4 Carbon fiber diffusion layer Catalyst layer Ionomer (e.g. proton exchange membrane)

  7. Acknowledgement • NSERC • Discovery Grant • Equipment Grant • BC ASI • Provincial Research Fellow • WED / CFI • Auto 21 • Industrial collaborations • Consultant for: Vizon Sci Tech. (2002-2003) Colgate-Palmolive USA (2005) Tekion (2006-2007)

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